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1 acpi= [HW,ACPI,X86,ARM64]
2 Advanced Configuration and Power Interface
3 Format: { force | on | off | strict | noirq | rsdt |
4 copy_dsdt }
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
10 strictly ACPI specification compliant.
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
14 are available
15
16 See also Documentation/power/runtime_pm.txt, pci=noacpi
17
18 acpi_apic_instance= [ACPI, IOAPIC]
19 Format: <int>
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
22 default: 0
23
24 acpi_backlight= [HW,ACPI]
25 acpi_backlight=vendor
26 acpi_backlight=video
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
30
31 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
36
37 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
44
45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
47 Format: <int>
48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
58
59 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
63 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
68
69 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
72
73 acpi_enforce_resources= [ACPI]
74 { strict | lax | no }
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
88
89 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
92 size limitation.
93
94 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
96 default in APIC mode
97
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
100 default in PIC mode
101
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
104
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
106 use by PCI
107 Format: <irq>,<irq>...
108
109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
113 the GPE dispatcher.
114 This facility can be used to prevent such uncontrolled
115 GPE floodings.
116 Format: <int>
117
118 acpi_no_auto_serialize [HW,ACPI]
119 Disable auto-serialization of AML methods
120 AML control methods that contain the opcodes to create
121 named objects will be marked as "Serialized" by the
122 auto-serialization feature.
123 This feature is enabled by default.
124 This option allows to turn off the feature.
125
126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
127 kernels.
128
129 acpi_no_static_ssdt [HW,ACPI]
130 Disable installation of static SSDTs at early boot time
131 By default, SSDTs contained in the RSDT/XSDT will be
132 installed automatically and they will appear under
133 /sys/firmware/acpi/tables.
134 This option turns off this feature.
135 Note that specifying this option does not affect
136 dynamic table installation which will install SSDT
137 tables to /sys/firmware/acpi/tables/dynamic.
138
139 acpi_rsdp= [ACPI,EFI,KEXEC]
140 Pass the RSDP address to the kernel, mostly used
141 on machines running EFI runtime service to boot the
142 second kernel for kdump.
143
144 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
145 Format: To spoof as Windows 98: ="Microsoft Windows"
146
147 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
148 of 2 which is mandated by ACPI 6) as the supported ACPI
149 specification revision (when using this switch, it may
150 be necessary to carry out a cold reboot _twice_ in a
151 row to make it take effect on the platform firmware).
152
153 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
154 acpi_osi="string1" # add string1
155 acpi_osi="!string2" # remove string2
156 acpi_osi=!* # remove all strings
157 acpi_osi=! # disable all built-in OS vendor
158 strings
159 acpi_osi=!! # enable all built-in OS vendor
160 strings
161 acpi_osi= # disable all strings
162
163 'acpi_osi=!' can be used in combination with single or
164 multiple 'acpi_osi="string1"' to support specific OS
165 vendor string(s). Note that such command can only
166 affect the default state of the OS vendor strings, thus
167 it cannot affect the default state of the feature group
168 strings and the current state of the OS vendor strings,
169 specifying it multiple times through kernel command line
170 is meaningless. This command is useful when one do not
171 care about the state of the feature group strings which
172 should be controlled by the OSPM.
173 Examples:
174 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
175 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
176 can make '_OSI("Windows 2000")' TRUE.
177
178 'acpi_osi=' cannot be used in combination with other
179 'acpi_osi=' command lines, the _OSI method will not
180 exist in the ACPI namespace. NOTE that such command can
181 only affect the _OSI support state, thus specifying it
182 multiple times through kernel command line is also
183 meaningless.
184 Examples:
185 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
186 FALSE.
187
188 'acpi_osi=!*' can be used in combination with single or
189 multiple 'acpi_osi="string1"' to support specific
190 string(s). Note that such command can affect the
191 current state of both the OS vendor strings and the
192 feature group strings, thus specifying it multiple times
193 through kernel command line is meaningful. But it may
194 still not able to affect the final state of a string if
195 there are quirks related to this string. This command
196 is useful when one want to control the state of the
197 feature group strings to debug BIOS issues related to
198 the OSPM features.
199 Examples:
200 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
201 '_OSI("Module Device")' FALSE.
202 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
203 '_OSI("Module Device")' TRUE.
204 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
205 equivalent to
206 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
207 and
208 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
209 they all will make '_OSI("Windows 2000")' TRUE.
210
211 acpi_pm_good [X86]
212 Override the pmtimer bug detection: force the kernel
213 to assume that this machine's pmtimer latches its value
214 and always returns good values.
215
216 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
217 Format: { level | edge | high | low }
218
219 acpi_skip_timer_override [HW,ACPI]
220 Recognize and ignore IRQ0/pin2 Interrupt Override.
221 For broken nForce2 BIOS resulting in XT-PIC timer.
222
223 acpi_sleep= [HW,ACPI] Sleep options
224 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
225 old_ordering, nonvs, sci_force_enable, nobl }
226 See Documentation/power/video.txt for information on
227 s3_bios and s3_mode.
228 s3_beep is for debugging; it makes the PC's speaker beep
229 as soon as the kernel's real-mode entry point is called.
230 s4_nohwsig prevents ACPI hardware signature from being
231 used during resume from hibernation.
232 old_ordering causes the ACPI 1.0 ordering of the _PTS
233 control method, with respect to putting devices into
234 low power states, to be enforced (the ACPI 2.0 ordering
235 of _PTS is used by default).
236 nonvs prevents the kernel from saving/restoring the
237 ACPI NVS memory during suspend/hibernation and resume.
238 sci_force_enable causes the kernel to set SCI_EN directly
239 on resume from S1/S3 (which is against the ACPI spec,
240 but some broken systems don't work without it).
241 nobl causes the internal blacklist of systems known to
242 behave incorrectly in some ways with respect to system
243 suspend and resume to be ignored (use wisely).
244
245 acpi_use_timer_override [HW,ACPI]
246 Use timer override. For some broken Nvidia NF5 boards
247 that require a timer override, but don't have HPET
248
249 add_efi_memmap [EFI; X86] Include EFI memory map in
250 kernel's map of available physical RAM.
251
252 agp= [AGP]
253 { off | try_unsupported }
254 off: disable AGP support
255 try_unsupported: try to drive unsupported chipsets
256 (may crash computer or cause data corruption)
257
258 ALSA [HW,ALSA]
259 See Documentation/sound/alsa/alsa-parameters.txt
260
261 alignment= [KNL,ARM]
262 Allow the default userspace alignment fault handler
263 behaviour to be specified. Bit 0 enables warnings,
264 bit 1 enables fixups, and bit 2 sends a segfault.
265
266 align_va_addr= [X86-64]
267 Align virtual addresses by clearing slice [14:12] when
268 allocating a VMA at process creation time. This option
269 gives you up to 3% performance improvement on AMD F15h
270 machines (where it is enabled by default) for a
271 CPU-intensive style benchmark, and it can vary highly in
272 a microbenchmark depending on workload and compiler.
273
274 32: only for 32-bit processes
275 64: only for 64-bit processes
276 on: enable for both 32- and 64-bit processes
277 off: disable for both 32- and 64-bit processes
278
279 alloc_snapshot [FTRACE]
280 Allocate the ftrace snapshot buffer on boot up when the
281 main buffer is allocated. This is handy if debugging
282 and you need to use tracing_snapshot() on boot up, and
283 do not want to use tracing_snapshot_alloc() as it needs
284 to be done where GFP_KERNEL allocations are allowed.
285
286 amd_iommu= [HW,X86-64]
287 Pass parameters to the AMD IOMMU driver in the system.
288 Possible values are:
289 fullflush - enable flushing of IO/TLB entries when
290 they are unmapped. Otherwise they are
291 flushed before they will be reused, which
292 is a lot of faster
293 off - do not initialize any AMD IOMMU found in
294 the system
295 force_isolation - Force device isolation for all
296 devices. The IOMMU driver is not
297 allowed anymore to lift isolation
298 requirements as needed. This option
299 does not override iommu=pt
300
301 amd_iommu_dump= [HW,X86-64]
302 Enable AMD IOMMU driver option to dump the ACPI table
303 for AMD IOMMU. With this option enabled, AMD IOMMU
304 driver will print ACPI tables for AMD IOMMU during
305 IOMMU initialization.
306
307 amd_iommu_intr= [HW,X86-64]
308 Specifies one of the following AMD IOMMU interrupt
309 remapping modes:
310 legacy - Use legacy interrupt remapping mode.
311 vapic - Use virtual APIC mode, which allows IOMMU
312 to inject interrupts directly into guest.
313 This mode requires kvm-amd.avic=1.
314 (Default when IOMMU HW support is present.)
315
316 amijoy.map= [HW,JOY] Amiga joystick support
317 Map of devices attached to JOY0DAT and JOY1DAT
318 Format: <a>,<b>
319 See also Documentation/input/joydev/joystick.rst
320
321 analog.map= [HW,JOY] Analog joystick and gamepad support
322 Specifies type or capabilities of an analog joystick
323 connected to one of 16 gameports
324 Format: <type1>,<type2>,..<type16>
325
326 apc= [HW,SPARC]
327 Power management functions (SPARCstation-4/5 + deriv.)
328 Format: noidle
329 Disable APC CPU standby support. SPARCstation-Fox does
330 not play well with APC CPU idle - disable it if you have
331 APC and your system crashes randomly.
332
333 apic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Change the output verbosity whilst booting
335 Format: { quiet (default) | verbose | debug }
336 Change the amount of debugging information output
337 when initialising the APIC and IO-APIC components.
338 For X86-32, this can also be used to specify an APIC
339 driver name.
340 Format: apic=driver_name
341 Examples: apic=bigsmp
342
343 apic_extnmi= [APIC,X86] External NMI delivery setting
344 Format: { bsp (default) | all | none }
345 bsp: External NMI is delivered only to CPU 0
346 all: External NMIs are broadcast to all CPUs as a
347 backup of CPU 0
348 none: External NMI is masked for all CPUs. This is
349 useful so that a dump capture kernel won't be
350 shot down by NMI
351
352 autoconf= [IPV6]
353 See Documentation/networking/ipv6.txt.
354
355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
363
364 apm= [APM] Advanced Power Management
365 See header of arch/x86/kernel/apm_32.c.
366
367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
369
370 ataflop= [HW,M68k]
371
372 atarimouse= [HW,MOUSE] Atari Mouse
373
374 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
375 EzKey and similar keyboards
376
377 atkbd.reset= [HW] Reset keyboard during initialization
378
379 atkbd.set= [HW] Select keyboard code set
380 Format: <int> (2 = AT (default), 3 = PS/2)
381
382 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
383 keyboards
384
385 atkbd.softraw= [HW] Choose between synthetic and real raw mode
386 Format: <bool> (0 = real, 1 = synthetic (default))
387
388 atkbd.softrepeat= [HW]
389 Use software keyboard repeat
390
391 audit= [KNL] Enable the audit sub-system
392 Format: { "0" | "1" | "off" | "on" }
393 0 | off - kernel audit is disabled and can not be
394 enabled until the next reboot
395 unset - kernel audit is initialized but disabled and
396 will be fully enabled by the userspace auditd.
397 1 | on - kernel audit is initialized and partially
398 enabled, storing at most audit_backlog_limit
399 messages in RAM until it is fully enabled by the
400 userspace auditd.
401 Default: unset
402
403 audit_backlog_limit= [KNL] Set the audit queue size limit.
404 Format: <int> (must be >=0)
405 Default: 64
406
407 bau= [X86_UV] Enable the BAU on SGI UV. The default
408 behavior is to disable the BAU (i.e. bau=0).
409 Format: { "0" | "1" }
410 0 - Disable the BAU.
411 1 - Enable the BAU.
412 unset - Disable the BAU.
413
414 baycom_epp= [HW,AX25]
415 Format: <io>,<mode>
416
417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
418 Format: <io>,<mode>
419 See header of drivers/net/hamradio/baycom_par.c.
420
421 baycom_ser_fdx= [HW,AX25]
422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
423 Format: <io>,<irq>,<mode>[,<baud>]
424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
425
426 baycom_ser_hdx= [HW,AX25]
427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
428 Format: <io>,<irq>,<mode>
429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
430
431 blkdevparts= Manual partition parsing of block device(s) for
432 embedded devices based on command line input.
433 See Documentation/block/cmdline-partition.txt
434
435 boot_delay= Milliseconds to delay each printk during boot.
436 Values larger than 10 seconds (10000) are changed to
437 no delay (0).
438 Format: integer
439
440 bootmem_debug [KNL] Enable bootmem allocator debug messages.
441
442 bert_disable [ACPI]
443 Disable BERT OS support on buggy BIOSes.
444
445 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
446 bttv.radio= Most important insmod options are available as
447 kernel args too.
448 bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
449 bttv.tuner=
450
451 bulk_remove=off [PPC] This parameter disables the use of the pSeries
452 firmware feature for flushing multiple hpte entries
453 at a time.
454
455 c101= [NET] Moxa C101 synchronous serial card
456
457 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
458 Sometimes CPU hardware bugs make them report the cache
459 size incorrectly. The kernel will attempt work arounds
460 to fix known problems, but for some CPUs it is not
461 possible to determine what the correct size should be.
462 This option provides an override for these situations.
463
464 ca_keys= [KEYS] This parameter identifies a specific key(s) on
465 the system trusted keyring to be used for certificate
466 trust validation.
467 format: { id:<keyid> | builtin }
468
469 cca= [MIPS] Override the kernel pages' cache coherency
470 algorithm. Accepted values range from 0 to 7
471 inclusive. See arch/mips/include/asm/pgtable-bits.h
472 for platform specific values (SB1, Loongson3 and
473 others).
474
475 ccw_timeout_log [S390]
476 See Documentation/s390/CommonIO for details.
477
478 cgroup_disable= [KNL] Disable a particular controller
479 Format: {name of the controller(s) to disable}
480 The effects of cgroup_disable=foo are:
481 - foo isn't auto-mounted if you mount all cgroups in
482 a single hierarchy
483 - foo isn't visible as an individually mountable
484 subsystem
485 {Currently only "memory" controller deal with this and
486 cut the overhead, others just disable the usage. So
487 only cgroup_disable=memory is actually worthy}
488
489 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
490 Format: { controller[,controller...] | "all" }
491 Like cgroup_disable, but only applies to cgroup v1;
492 the blacklisted controllers remain available in cgroup2.
493
494 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
495 Format: <string>
496 nosocket -- Disable socket memory accounting.
497 nokmem -- Disable kernel memory accounting.
498
499 checkreqprot [SELINUX] Set initial checkreqprot flag value.
500 Format: { "0" | "1" }
501 See security/selinux/Kconfig help text.
502 0 -- check protection applied by kernel (includes
503 any implied execute protection).
504 1 -- check protection requested by application.
505 Default value is set via a kernel config option.
506 Value can be changed at runtime via
507 /selinux/checkreqprot.
508
509 cio_ignore= [S390]
510 See Documentation/s390/CommonIO for details.
511 clk_ignore_unused
512 [CLK]
513 Prevents the clock framework from automatically gating
514 clocks that have not been explicitly enabled by a Linux
515 device driver but are enabled in hardware at reset or
516 by the bootloader/firmware. Note that this does not
517 force such clocks to be always-on nor does it reserve
518 those clocks in any way. This parameter is useful for
519 debug and development, but should not be needed on a
520 platform with proper driver support. For more
521 information, see Documentation/clk.txt.
522
523 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
524 [Deprecated]
525 Forces specified clocksource (if available) to be used
526 when calculating gettimeofday(). If specified
527 clocksource is not available, it defaults to PIT.
528 Format: { pit | tsc | cyclone | pmtmr }
529
530 clocksource= Override the default clocksource
531 Format: <string>
532 Override the default clocksource and use the clocksource
533 with the name specified.
534 Some clocksource names to choose from, depending on
535 the platform:
536 [all] jiffies (this is the base, fallback clocksource)
537 [ACPI] acpi_pm
538 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
539 pxa_timer,timer3,32k_counter,timer0_1
540 [X86-32] pit,hpet,tsc;
541 scx200_hrt on Geode; cyclone on IBM x440
542 [MIPS] MIPS
543 [PARISC] cr16
544 [S390] tod
545 [SH] SuperH
546 [SPARC64] tick
547 [X86-64] hpet,tsc
548
549 clocksource.arm_arch_timer.evtstrm=
550 [ARM,ARM64]
551 Format: <bool>
552 Enable/disable the eventstream feature of the ARM
553 architected timer so that code using WFE-based polling
554 loops can be debugged more effectively on production
555 systems.
556
557 clearcpuid=BITNUM [X86]
558 Disable CPUID feature X for the kernel. See
559 arch/x86/include/asm/cpufeatures.h for the valid bit
560 numbers. Note the Linux specific bits are not necessarily
561 stable over kernel options, but the vendor specific
562 ones should be.
563 Also note that user programs calling CPUID directly
564 or using the feature without checking anything
565 will still see it. This just prevents it from
566 being used by the kernel or shown in /proc/cpuinfo.
567 Also note the kernel might malfunction if you disable
568 some critical bits.
569
570 cma=nn[MG]@[start[MG][-end[MG]]]
571 [ARM,X86,KNL]
572 Sets the size of kernel global memory area for
573 contiguous memory allocations and optionally the
574 placement constraint by the physical address range of
575 memory allocations. A value of 0 disables CMA
576 altogether. For more information, see
577 include/linux/dma-contiguous.h
578
579 cmo_free_hint= [PPC] Format: { yes | no }
580 Specify whether pages are marked as being inactive
581 when they are freed. This is used in CMO environments
582 to determine OS memory pressure for page stealing by
583 a hypervisor.
584 Default: yes
585
586 coherent_pool=nn[KMG] [ARM,KNL]
587 Sets the size of memory pool for coherent, atomic dma
588 allocations, by default set to 256K.
589
590 code_bytes [X86] How many bytes of object code to print
591 in an oops report.
592 Range: 0 - 8192
593 Default: 64
594
595 com20020= [HW,NET] ARCnet - COM20020 chipset
596 Format:
597 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
598
599 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
600 Format: <io>[,<irq>]
601
602 com90xx= [HW,NET]
603 ARCnet - COM90xx chipset (memory-mapped buffers)
604 Format: <io>[,<irq>[,<memstart>]]
605
606 condev= [HW,S390] console device
607 conmode=
608
609 console= [KNL] Output console device and options.
610
611 tty<n> Use the virtual console device <n>.
612
613 ttyS<n>[,options]
614 ttyUSB0[,options]
615 Use the specified serial port. The options are of
616 the form "bbbbpnf", where "bbbb" is the baud rate,
617 "p" is parity ("n", "o", or "e"), "n" is number of
618 bits, and "f" is flow control ("r" for RTS or
619 omit it). Default is "9600n8".
620
621 See Documentation/admin-guide/serial-console.rst for more
622 information. See
623 Documentation/networking/netconsole.txt for an
624 alternative.
625
626 uart[8250],io,<addr>[,options]
627 uart[8250],mmio,<addr>[,options]
628 uart[8250],mmio16,<addr>[,options]
629 uart[8250],mmio32,<addr>[,options]
630 uart[8250],0x<addr>[,options]
631 Start an early, polled-mode console on the 8250/16550
632 UART at the specified I/O port or MMIO address,
633 switching to the matching ttyS device later.
634 MMIO inter-register address stride is either 8-bit
635 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
636 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
637 to be equivalent to 'mmio'. 'options' are specified in
638 the same format described for ttyS above; if unspecified,
639 the h/w is not re-initialized.
640
641 hvc<n> Use the hypervisor console device <n>. This is for
642 both Xen and PowerPC hypervisors.
643
644 If the device connected to the port is not a TTY but a braille
645 device, prepend "brl," before the device type, for instance
646 console=brl,ttyS0
647 For now, only VisioBraille is supported.
648
649 console_msg_format=
650 [KNL] Change console messages format
651 default
652 By default we print messages on consoles in
653 "[time stamp] text\n" format (time stamp may not be
654 printed, depending on CONFIG_PRINTK_TIME or
655 `printk_time' param).
656 syslog
657 Switch to syslog format: "<%u>[time stamp] text\n"
658 IOW, each message will have a facility and loglevel
659 prefix. The format is similar to one used by syslog()
660 syscall, or to executing "dmesg -S --raw" or to reading
661 from /proc/kmsg.
662
663 consoleblank= [KNL] The console blank (screen saver) timeout in
664 seconds. A value of 0 disables the blank timer.
665 Defaults to 0.
666
667 coredump_filter=
668 [KNL] Change the default value for
669 /proc/<pid>/coredump_filter.
670 See also Documentation/filesystems/proc.txt.
671
672 coresight_cpu_debug.enable
673 [ARM,ARM64]
674 Format: <bool>
675 Enable/disable the CPU sampling based debugging.
676 0: default value, disable debugging
677 1: enable debugging at boot time
678
679 cpuidle.off=1 [CPU_IDLE]
680 disable the cpuidle sub-system
681
682 cpufreq.off=1 [CPU_FREQ]
683 disable the cpufreq sub-system
684
685 cpu_init_udelay=N
686 [X86] Delay for N microsec between assert and de-assert
687 of APIC INIT to start processors. This delay occurs
688 on every CPU online, such as boot, and resume from suspend.
689 Default: 10000
690
691 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
692 Format:
693 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
694
695 crashkernel=size[KMG][@offset[KMG]]
696 [KNL] Using kexec, Linux can switch to a 'crash kernel'
697 upon panic. This parameter reserves the physical
698 memory region [offset, offset + size] for that kernel
699 image. If '@offset' is omitted, then a suitable offset
700 is selected automatically. Check
701 Documentation/kdump/kdump.txt for further details.
702
703 crashkernel=range1:size1[,range2:size2,...][@offset]
704 [KNL] Same as above, but depends on the memory
705 in the running system. The syntax of range is
706 start-[end] where start and end are both
707 a memory unit (amount[KMG]). See also
708 Documentation/kdump/kdump.txt for an example.
709
710 crashkernel=size[KMG],high
711 [KNL, x86_64] range could be above 4G. Allow kernel
712 to allocate physical memory region from top, so could
713 be above 4G if system have more than 4G ram installed.
714 Otherwise memory region will be allocated below 4G, if
715 available.
716 It will be ignored if crashkernel=X is specified.
717 crashkernel=size[KMG],low
718 [KNL, x86_64] range under 4G. When crashkernel=X,high
719 is passed, kernel could allocate physical memory region
720 above 4G, that cause second kernel crash on system
721 that require some amount of low memory, e.g. swiotlb
722 requires at least 64M+32K low memory, also enough extra
723 low memory is needed to make sure DMA buffers for 32-bit
724 devices won't run out. Kernel would try to allocate at
725 at least 256M below 4G automatically.
726 This one let user to specify own low range under 4G
727 for second kernel instead.
728 0: to disable low allocation.
729 It will be ignored when crashkernel=X,high is not used
730 or memory reserved is below 4G.
731
732 cryptomgr.notests
733 [KNL] Disable crypto self-tests
734
735 cs89x0_dma= [HW,NET]
736 Format: <dma>
737
738 cs89x0_media= [HW,NET]
739 Format: { rj45 | aui | bnc }
740
741 dasd= [HW,NET]
742 See header of drivers/s390/block/dasd_devmap.c.
743
744 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
745 (one device per port)
746 Format: <port#>,<type>
747 See also Documentation/input/devices/joystick-parport.rst
748
749 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
750 time. See
751 Documentation/admin-guide/dynamic-debug-howto.rst for
752 details. Deprecated, see dyndbg.
753
754 debug [KNL] Enable kernel debugging (events log level).
755
756 debug_locks_verbose=
757 [KNL] verbose self-tests
758 Format=<0|1>
759 Print debugging info while doing the locking API
760 self-tests.
761 We default to 0 (no extra messages), setting it to
762 1 will print _a lot_ more information - normally
763 only useful to kernel developers.
764
765 debug_objects [KNL] Enable object debugging
766
767 no_debug_objects
768 [KNL] Disable object debugging
769
770 debug_guardpage_minorder=
771 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
772 parameter allows control of the order of pages that will
773 be intentionally kept free (and hence protected) by the
774 buddy allocator. Bigger value increase the probability
775 of catching random memory corruption, but reduce the
776 amount of memory for normal system use. The maximum
777 possible value is MAX_ORDER/2. Setting this parameter
778 to 1 or 2 should be enough to identify most random
779 memory corruption problems caused by bugs in kernel or
780 driver code when a CPU writes to (or reads from) a
781 random memory location. Note that there exists a class
782 of memory corruptions problems caused by buggy H/W or
783 F/W or by drivers badly programing DMA (basically when
784 memory is written at bus level and the CPU MMU is
785 bypassed) which are not detectable by
786 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
787 tracking down these problems.
788
789 debug_pagealloc=
790 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
791 parameter enables the feature at boot time. In
792 default, it is disabled. We can avoid allocating huge
793 chunk of memory for debug pagealloc if we don't enable
794 it at boot time and the system will work mostly same
795 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
796 on: enable the feature
797
798 debugpat [X86] Enable PAT debugging
799
800 decnet.addr= [HW,NET]
801 Format: <area>[,<node>]
802 See also Documentation/networking/decnet.txt.
803
804 default_hugepagesz=
805 [same as hugepagesz=] The size of the default
806 HugeTLB page size. This is the size represented by
807 the legacy /proc/ hugepages APIs, used for SHM, and
808 default size when mounting hugetlbfs filesystems.
809 Defaults to the default architecture's huge page size
810 if not specified.
811
812 dhash_entries= [KNL]
813 Set number of hash buckets for dentry cache.
814
815 disable_1tb_segments [PPC]
816 Disables the use of 1TB hash page table segments. This
817 causes the kernel to fall back to 256MB segments which
818 can be useful when debugging issues that require an SLB
819 miss to occur.
820
821 disable= [IPV6]
822 See Documentation/networking/ipv6.txt.
823
824 disable_radix [PPC]
825 Disable RADIX MMU mode on POWER9
826
827 disable_cpu_apicid= [X86,APIC,SMP]
828 Format: <int>
829 The number of initial APIC ID for the
830 corresponding CPU to be disabled at boot,
831 mostly used for the kdump 2nd kernel to
832 disable BSP to wake up multiple CPUs without
833 causing system reset or hang due to sending
834 INIT from AP to BSP.
835
836 disable_ddw [PPC/PSERIES]
837 Disable Dynamic DMA Window support. Use this if
838 to workaround buggy firmware.
839
840 disable_ipv6= [IPV6]
841 See Documentation/networking/ipv6.txt.
842
843 disable_mtrr_cleanup [X86]
844 The kernel tries to adjust MTRR layout from continuous
845 to discrete, to make X server driver able to add WB
846 entry later. This parameter disables that.
847
848 disable_mtrr_trim [X86, Intel and AMD only]
849 By default the kernel will trim any uncacheable
850 memory out of your available memory pool based on
851 MTRR settings. This parameter disables that behavior,
852 possibly causing your machine to run very slowly.
853
854 disable_timer_pin_1 [X86]
855 Disable PIN 1 of APIC timer
856 Can be useful to work around chipset bugs.
857
858 dis_ucode_ldr [X86] Disable the microcode loader.
859
860 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
861 this option disables the debugging code at boot.
862
863 dma_debug_entries=<number>
864 This option allows to tune the number of preallocated
865 entries for DMA-API debugging code. One entry is
866 required per DMA-API allocation. Use this if the
867 DMA-API debugging code disables itself because the
868 architectural default is too low.
869
870 dma_debug_driver=<driver_name>
871 With this option the DMA-API debugging driver
872 filter feature can be enabled at boot time. Just
873 pass the driver to filter for as the parameter.
874 The filter can be disabled or changed to another
875 driver later using sysfs.
876
877 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
878 Broken monitors, graphic adapters, KVMs and EDIDless
879 panels may send no or incorrect EDID data sets.
880 This parameter allows to specify an EDID data sets
881 in the /lib/firmware directory that are used instead.
882 Generic built-in EDID data sets are used, if one of
883 edid/1024x768.bin, edid/1280x1024.bin,
884 edid/1680x1050.bin, or edid/1920x1080.bin is given
885 and no file with the same name exists. Details and
886 instructions how to build your own EDID data are
887 available in Documentation/EDID/HOWTO.txt. An EDID
888 data set will only be used for a particular connector,
889 if its name and a colon are prepended to the EDID
890 name. Each connector may use a unique EDID data
891 set by separating the files with a comma. An EDID
892 data set with no connector name will be used for
893 any connectors not explicitly specified.
894
895 dscc4.setup= [NET]
896
897 dt_cpu_ftrs= [PPC]
898 Format: {"off" | "known"}
899 Control how the dt_cpu_ftrs device-tree binding is
900 used for CPU feature discovery and setup (if it
901 exists).
902 off: Do not use it, fall back to legacy cpu table.
903 known: Do not pass through unknown features to guests
904 or userspace, only those that the kernel is aware of.
905
906 dump_apple_properties [X86]
907 Dump name and content of EFI device properties on
908 x86 Macs. Useful for driver authors to determine
909 what data is available or for reverse-engineering.
910
911 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
912 module.dyndbg[="val"]
913 Enable debug messages at boot time. See
914 Documentation/admin-guide/dynamic-debug-howto.rst
915 for details.
916
917 nompx [X86] Disables Intel Memory Protection Extensions.
918 See Documentation/x86/intel_mpx.txt for more
919 information about the feature.
920
921 nopku [X86] Disable Memory Protection Keys CPU feature found
922 in some Intel CPUs.
923
924 module.async_probe [KNL]
925 Enable asynchronous probe on this module.
926
927 early_ioremap_debug [KNL]
928 Enable debug messages in early_ioremap support. This
929 is useful for tracking down temporary early mappings
930 which are not unmapped.
931
932 earlycon= [KNL] Output early console device and options.
933
934 [ARM64] The early console is determined by the
935 stdout-path property in device tree's chosen node,
936 or determined by the ACPI SPCR table.
937
938 [X86] When used with no options the early console is
939 determined by the ACPI SPCR table.
940
941 cdns,<addr>[,options]
942 Start an early, polled-mode console on a Cadence
943 (xuartps) serial port at the specified address. Only
944 supported option is baud rate. If baud rate is not
945 specified, the serial port must already be setup and
946 configured.
947
948 uart[8250],io,<addr>[,options]
949 uart[8250],mmio,<addr>[,options]
950 uart[8250],mmio32,<addr>[,options]
951 uart[8250],mmio32be,<addr>[,options]
952 uart[8250],0x<addr>[,options]
953 Start an early, polled-mode console on the 8250/16550
954 UART at the specified I/O port or MMIO address.
955 MMIO inter-register address stride is either 8-bit
956 (mmio) or 32-bit (mmio32 or mmio32be).
957 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
958 to be equivalent to 'mmio'. 'options' are specified
959 in the same format described for "console=ttyS<n>"; if
960 unspecified, the h/w is not initialized.
961
962 pl011,<addr>
963 pl011,mmio32,<addr>
964 Start an early, polled-mode console on a pl011 serial
965 port at the specified address. The pl011 serial port
966 must already be setup and configured. Options are not
967 yet supported. If 'mmio32' is specified, then only
968 the driver will use only 32-bit accessors to read/write
969 the device registers.
970
971 meson,<addr>
972 Start an early, polled-mode console on a meson serial
973 port at the specified address. The serial port must
974 already be setup and configured. Options are not yet
975 supported.
976
977 msm_serial,<addr>
978 Start an early, polled-mode console on an msm serial
979 port at the specified address. The serial port
980 must already be setup and configured. Options are not
981 yet supported.
982
983 msm_serial_dm,<addr>
984 Start an early, polled-mode console on an msm serial
985 dm port at the specified address. The serial port
986 must already be setup and configured. Options are not
987 yet supported.
988
989 owl,<addr>
990 Start an early, polled-mode console on a serial port
991 of an Actions Semi SoC, such as S500 or S900, at the
992 specified address. The serial port must already be
993 setup and configured. Options are not yet supported.
994
995 smh Use ARM semihosting calls for early console.
996
997 s3c2410,<addr>
998 s3c2412,<addr>
999 s3c2440,<addr>
1000 s3c6400,<addr>
1001 s5pv210,<addr>
1002 exynos4210,<addr>
1003 Use early console provided by serial driver available
1004 on Samsung SoCs, requires selecting proper type and
1005 a correct base address of the selected UART port. The
1006 serial port must already be setup and configured.
1007 Options are not yet supported.
1008
1009 lantiq,<addr>
1010 Start an early, polled-mode console on a lantiq serial
1011 (lqasc) port at the specified address. The serial port
1012 must already be setup and configured. Options are not
1013 yet supported.
1014
1015 lpuart,<addr>
1016 lpuart32,<addr>
1017 Use early console provided by Freescale LP UART driver
1018 found on Freescale Vybrid and QorIQ LS1021A processors.
1019 A valid base address must be provided, and the serial
1020 port must already be setup and configured.
1021
1022 ar3700_uart,<addr>
1023 Start an early, polled-mode console on the
1024 Armada 3700 serial port at the specified
1025 address. The serial port must already be setup
1026 and configured. Options are not yet supported.
1027
1028 earlyprintk= [X86,SH,ARM,M68k,S390]
1029 earlyprintk=vga
1030 earlyprintk=efi
1031 earlyprintk=sclp
1032 earlyprintk=xen
1033 earlyprintk=serial[,ttySn[,baudrate]]
1034 earlyprintk=serial[,0x...[,baudrate]]
1035 earlyprintk=ttySn[,baudrate]
1036 earlyprintk=dbgp[debugController#]
1037 earlyprintk=pciserial,bus:device.function[,baudrate]
1038 earlyprintk=xdbc[xhciController#]
1039
1040 earlyprintk is useful when the kernel crashes before
1041 the normal console is initialized. It is not enabled by
1042 default because it has some cosmetic problems.
1043
1044 Append ",keep" to not disable it when the real console
1045 takes over.
1046
1047 Only one of vga, efi, serial, or usb debug port can
1048 be used at a time.
1049
1050 Currently only ttyS0 and ttyS1 may be specified by
1051 name. Other I/O ports may be explicitly specified
1052 on some architectures (x86 and arm at least) by
1053 replacing ttySn with an I/O port address, like this:
1054 earlyprintk=serial,0x1008,115200
1055 You can find the port for a given device in
1056 /proc/tty/driver/serial:
1057 2: uart:ST16650V2 port:00001008 irq:18 ...
1058
1059 Interaction with the standard serial driver is not
1060 very good.
1061
1062 The VGA and EFI output is eventually overwritten by
1063 the real console.
1064
1065 The xen output can only be used by Xen PV guests.
1066
1067 The sclp output can only be used on s390.
1068
1069 edac_report= [HW,EDAC] Control how to report EDAC event
1070 Format: {"on" | "off" | "force"}
1071 on: enable EDAC to report H/W event. May be overridden
1072 by other higher priority error reporting module.
1073 off: disable H/W event reporting through EDAC.
1074 force: enforce the use of EDAC to report H/W event.
1075 default: on.
1076
1077 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1078 ekgdboc=kbd
1079
1080 This is designed to be used in conjunction with
1081 the boot argument: earlyprintk=vga
1082
1083 edd= [EDD]
1084 Format: {"off" | "on" | "skip[mbr]"}
1085
1086 efi= [EFI]
1087 Format: { "old_map", "nochunk", "noruntime", "debug" }
1088 old_map [X86-64]: switch to the old ioremap-based EFI
1089 runtime services mapping. 32-bit still uses this one by
1090 default.
1091 nochunk: disable reading files in "chunks" in the EFI
1092 boot stub, as chunking can cause problems with some
1093 firmware implementations.
1094 noruntime : disable EFI runtime services support
1095 debug: enable misc debug output
1096
1097 efi_no_storage_paranoia [EFI; X86]
1098 Using this parameter you can use more than 50% of
1099 your efi variable storage. Use this parameter only if
1100 you are really sure that your UEFI does sane gc and
1101 fulfills the spec otherwise your board may brick.
1102
1103 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1104 Add arbitrary attribute to specific memory range by
1105 updating original EFI memory map.
1106 Region of memory which aa attribute is added to is
1107 from ss to ss+nn.
1108 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1109 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1110 attribute is added to range 0x100000000-0x180000000 and
1111 0x10a0000000-0x1120000000.
1112
1113 Using this parameter you can do debugging of EFI memmap
1114 related feature. For example, you can do debugging of
1115 Address Range Mirroring feature even if your box
1116 doesn't support it.
1117
1118 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1119 that is to be dynamically loaded by Linux. If there are
1120 multiple variables with the same name but with different
1121 vendor GUIDs, all of them will be loaded. See
1122 Documentation/acpi/ssdt-overlays.txt for details.
1123
1124
1125 eisa_irq_edge= [PARISC,HW]
1126 See header of drivers/parisc/eisa.c.
1127
1128 elanfreq= [X86-32]
1129 See comment before function elanfreq_setup() in
1130 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1131
1132 elevator= [IOSCHED]
1133 Format: {"cfq" | "deadline" | "noop"}
1134 See Documentation/block/cfq-iosched.txt and
1135 Documentation/block/deadline-iosched.txt for details.
1136
1137 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1138 Specifies physical address of start of kernel core
1139 image elf header and optionally the size. Generally
1140 kexec loader will pass this option to capture kernel.
1141 See Documentation/kdump/kdump.txt for details.
1142
1143 enable_mtrr_cleanup [X86]
1144 The kernel tries to adjust MTRR layout from continuous
1145 to discrete, to make X server driver able to add WB
1146 entry later. This parameter enables that.
1147
1148 enable_timer_pin_1 [X86]
1149 Enable PIN 1 of APIC timer
1150 Can be useful to work around chipset bugs
1151 (in particular on some ATI chipsets).
1152 The kernel tries to set a reasonable default.
1153
1154 enforcing [SELINUX] Set initial enforcing status.
1155 Format: {"0" | "1"}
1156 See security/selinux/Kconfig help text.
1157 0 -- permissive (log only, no denials).
1158 1 -- enforcing (deny and log).
1159 Default value is 0.
1160 Value can be changed at runtime via /selinux/enforce.
1161
1162 erst_disable [ACPI]
1163 Disable Error Record Serialization Table (ERST)
1164 support.
1165
1166 ether= [HW,NET] Ethernet cards parameters
1167 This option is obsoleted by the "netdev=" option, which
1168 has equivalent usage. See its documentation for details.
1169
1170 evm= [EVM]
1171 Format: { "fix" }
1172 Permit 'security.evm' to be updated regardless of
1173 current integrity status.
1174
1175 failslab=
1176 fail_page_alloc=
1177 fail_make_request=[KNL]
1178 General fault injection mechanism.
1179 Format: <interval>,<probability>,<space>,<times>
1180 See also Documentation/fault-injection/.
1181
1182 floppy= [HW]
1183 See Documentation/blockdev/floppy.txt.
1184
1185 force_pal_cache_flush
1186 [IA-64] Avoid check_sal_cache_flush which may hang on
1187 buggy SAL_CACHE_FLUSH implementations. Using this
1188 parameter will force ia64_sal_cache_flush to call
1189 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1190
1191 forcepae [X86-32]
1192 Forcefully enable Physical Address Extension (PAE).
1193 Many Pentium M systems disable PAE but may have a
1194 functionally usable PAE implementation.
1195 Warning: use of this parameter will taint the kernel
1196 and may cause unknown problems.
1197
1198 ftrace=[tracer]
1199 [FTRACE] will set and start the specified tracer
1200 as early as possible in order to facilitate early
1201 boot debugging.
1202
1203 ftrace_dump_on_oops[=orig_cpu]
1204 [FTRACE] will dump the trace buffers on oops.
1205 If no parameter is passed, ftrace will dump
1206 buffers of all CPUs, but if you pass orig_cpu, it will
1207 dump only the buffer of the CPU that triggered the
1208 oops.
1209
1210 ftrace_filter=[function-list]
1211 [FTRACE] Limit the functions traced by the function
1212 tracer at boot up. function-list is a comma separated
1213 list of functions. This list can be changed at run
1214 time by the set_ftrace_filter file in the debugfs
1215 tracing directory.
1216
1217 ftrace_notrace=[function-list]
1218 [FTRACE] Do not trace the functions specified in
1219 function-list. This list can be changed at run time
1220 by the set_ftrace_notrace file in the debugfs
1221 tracing directory.
1222
1223 ftrace_graph_filter=[function-list]
1224 [FTRACE] Limit the top level callers functions traced
1225 by the function graph tracer at boot up.
1226 function-list is a comma separated list of functions
1227 that can be changed at run time by the
1228 set_graph_function file in the debugfs tracing directory.
1229
1230 ftrace_graph_notrace=[function-list]
1231 [FTRACE] Do not trace from the functions specified in
1232 function-list. This list is a comma separated list of
1233 functions that can be changed at run time by the
1234 set_graph_notrace file in the debugfs tracing directory.
1235
1236 ftrace_graph_max_depth=<uint>
1237 [FTRACE] Used with the function graph tracer. This is
1238 the max depth it will trace into a function. This value
1239 can be changed at run time by the max_graph_depth file
1240 in the tracefs tracing directory. default: 0 (no limit)
1241
1242 gamecon.map[2|3]=
1243 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1244 support via parallel port (up to 5 devices per port)
1245 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1246 See also Documentation/input/devices/joystick-parport.rst
1247
1248 gamma= [HW,DRM]
1249
1250 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1251 Format: off | on
1252 default: on
1253
1254 gcov_persist= [GCOV] When non-zero (default), profiling data for
1255 kernel modules is saved and remains accessible via
1256 debugfs, even when the module is unloaded/reloaded.
1257 When zero, profiling data is discarded and associated
1258 debugfs files are removed at module unload time.
1259
1260 goldfish [X86] Enable the goldfish android emulator platform.
1261 Don't use this when you are not running on the
1262 android emulator
1263
1264 gpt [EFI] Forces disk with valid GPT signature but
1265 invalid Protective MBR to be treated as GPT. If the
1266 primary GPT is corrupted, it enables the backup/alternate
1267 GPT to be used instead.
1268
1269 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1270 the "Enable 0" bit of the configuration register.
1271 Format: 0 | 1
1272 Default: 0
1273 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1274 the "Enable 0" bit of the configuration register.
1275 Format: 0 | 1
1276 Default: 0
1277 grcan.select= [HW] Select which physical interface to use.
1278 Format: 0 | 1
1279 Default: 0
1280 grcan.txsize= [HW] Sets the size of the tx buffer.
1281 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1282 Default: 1024
1283 grcan.rxsize= [HW] Sets the size of the rx buffer.
1284 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1285 Default: 1024
1286
1287 gpio-mockup.gpio_mockup_ranges
1288 [HW] Sets the ranges of gpiochip of for this device.
1289 Format: <start1>,<end1>,<start2>,<end2>...
1290
1291 hardlockup_all_cpu_backtrace=
1292 [KNL] Should the hard-lockup detector generate
1293 backtraces on all cpus.
1294 Format: <integer>
1295
1296 hashdist= [KNL,NUMA] Large hashes allocated during boot
1297 are distributed across NUMA nodes. Defaults on
1298 for 64-bit NUMA, off otherwise.
1299 Format: 0 | 1 (for off | on)
1300
1301 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1302
1303 hd= [EIDE] (E)IDE hard drive subsystem geometry
1304 Format: <cyl>,<head>,<sect>
1305
1306 hest_disable [ACPI]
1307 Disable Hardware Error Source Table (HEST) support;
1308 corresponding firmware-first mode error processing
1309 logic will be disabled.
1310
1311 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1312 size of <nn>. This works even on boxes that have no
1313 highmem otherwise. This also works to reduce highmem
1314 size on bigger boxes.
1315
1316 highres= [KNL] Enable/disable high resolution timer mode.
1317 Valid parameters: "on", "off"
1318 Default: "on"
1319
1320 hisax= [HW,ISDN]
1321 See Documentation/isdn/README.HiSax.
1322
1323 hlt [BUGS=ARM,SH]
1324
1325 hpet= [X86-32,HPET] option to control HPET usage
1326 Format: { enable (default) | disable | force |
1327 verbose }
1328 disable: disable HPET and use PIT instead
1329 force: allow force enabled of undocumented chips (ICH4,
1330 VIA, nVidia)
1331 verbose: show contents of HPET registers during setup
1332
1333 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1334 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1335
1336 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1337 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1338 On x86-64 and powerpc, this option can be specified
1339 multiple times interleaved with hugepages= to reserve
1340 huge pages of different sizes. Valid pages sizes on
1341 x86-64 are 2M (when the CPU supports "pse") and 1G
1342 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1343
1344 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1345 terminal devices. Valid values: 0..8
1346 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1347 If specified, z/VM IUCV HVC accepts connections
1348 from listed z/VM user IDs only.
1349
1350 keep_bootcon [KNL]
1351 Do not unregister boot console at start. This is only
1352 useful for debugging when something happens in the window
1353 between unregistering the boot console and initializing
1354 the real console.
1355
1356 i2c_bus= [HW] Override the default board specific I2C bus speed
1357 or register an additional I2C bus that is not
1358 registered from board initialization code.
1359 Format:
1360 <bus_id>,<clkrate>
1361
1362 i8042.debug [HW] Toggle i8042 debug mode
1363 i8042.unmask_kbd_data
1364 [HW] Enable printing of interrupt data from the KBD port
1365 (disabled by default, and as a pre-condition
1366 requires that i8042.debug=1 be enabled)
1367 i8042.direct [HW] Put keyboard port into non-translated mode
1368 i8042.dumbkbd [HW] Pretend that controller can only read data from
1369 keyboard and cannot control its state
1370 (Don't attempt to blink the leds)
1371 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1372 i8042.nokbd [HW] Don't check/create keyboard port
1373 i8042.noloop [HW] Disable the AUX Loopback command while probing
1374 for the AUX port
1375 i8042.nomux [HW] Don't check presence of an active multiplexing
1376 controller
1377 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1378 controllers
1379 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1380 i8042.reset [HW] Reset the controller during init, cleanup and
1381 suspend-to-ram transitions, only during s2r
1382 transitions, or never reset
1383 Format: { 1 | Y | y | 0 | N | n }
1384 1, Y, y: always reset controller
1385 0, N, n: don't ever reset controller
1386 Default: only on s2r transitions on x86; most other
1387 architectures force reset to be always executed
1388 i8042.unlock [HW] Unlock (ignore) the keylock
1389 i8042.kbdreset [HW] Reset device connected to KBD port
1390
1391 i810= [HW,DRM]
1392
1393 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1394 indicates that the driver is running on unsupported
1395 hardware.
1396 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1397 does not match list of supported models.
1398 i8k.power_status
1399 [HW] Report power status in /proc/i8k
1400 (disabled by default)
1401 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1402 capability is set.
1403
1404 i915.invert_brightness=
1405 [DRM] Invert the sense of the variable that is used to
1406 set the brightness of the panel backlight. Normally a
1407 brightness value of 0 indicates backlight switched off,
1408 and the maximum of the brightness value sets the backlight
1409 to maximum brightness. If this parameter is set to 0
1410 (default) and the machine requires it, or this parameter
1411 is set to 1, a brightness value of 0 sets the backlight
1412 to maximum brightness, and the maximum of the brightness
1413 value switches the backlight off.
1414 -1 -- never invert brightness
1415 0 -- machine default
1416 1 -- force brightness inversion
1417
1418 icn= [HW,ISDN]
1419 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1420
1421 ide-core.nodma= [HW] (E)IDE subsystem
1422 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1423 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1424 .cdrom .chs .ignore_cable are additional options
1425 See Documentation/ide/ide.txt.
1426
1427 ide-generic.probe-mask= [HW] (E)IDE subsystem
1428 Format: <int>
1429 Probe mask for legacy ISA IDE ports. Depending on
1430 platform up to 6 ports are supported, enabled by
1431 setting corresponding bits in the mask to 1. The
1432 default value is 0x0, which has a special meaning.
1433 On systems that have PCI, it triggers scanning the
1434 PCI bus for the first and the second port, which
1435 are then probed. On systems without PCI the value
1436 of 0x0 enables probing the two first ports as if it
1437 was 0x3.
1438
1439 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1440 Claim all unknown PCI IDE storage controllers.
1441
1442 idle= [X86]
1443 Format: idle=poll, idle=halt, idle=nomwait
1444 Poll forces a polling idle loop that can slightly
1445 improve the performance of waking up a idle CPU, but
1446 will use a lot of power and make the system run hot.
1447 Not recommended.
1448 idle=halt: Halt is forced to be used for CPU idle.
1449 In such case C2/C3 won't be used again.
1450 idle=nomwait: Disable mwait for CPU C-states
1451
1452 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1453 Format: { strict | legacy | 2008 | relaxed }
1454 Default: strict
1455
1456 Choose which programs will be accepted for execution
1457 based on the IEEE 754 NaN encoding(s) supported by
1458 the FPU and the NaN encoding requested with the value
1459 of an ELF file header flag individually set by each
1460 binary. Hardware implementations are permitted to
1461 support either or both of the legacy and the 2008 NaN
1462 encoding mode.
1463
1464 Available settings are as follows:
1465 strict accept binaries that request a NaN encoding
1466 supported by the FPU
1467 legacy only accept legacy-NaN binaries, if supported
1468 by the FPU
1469 2008 only accept 2008-NaN binaries, if supported
1470 by the FPU
1471 relaxed accept any binaries regardless of whether
1472 supported by the FPU
1473
1474 The FPU emulator is always able to support both NaN
1475 encodings, so if no FPU hardware is present or it has
1476 been disabled with 'nofpu', then the settings of
1477 'legacy' and '2008' strap the emulator accordingly,
1478 'relaxed' straps the emulator for both legacy-NaN and
1479 2008-NaN, whereas 'strict' enables legacy-NaN only on
1480 legacy processors and both NaN encodings on MIPS32 or
1481 MIPS64 CPUs.
1482
1483 The setting for ABS.fmt/NEG.fmt instruction execution
1484 mode generally follows that for the NaN encoding,
1485 except where unsupported by hardware.
1486
1487 ignore_loglevel [KNL]
1488 Ignore loglevel setting - this will print /all/
1489 kernel messages to the console. Useful for debugging.
1490 We also add it as printk module parameter, so users
1491 could change it dynamically, usually by
1492 /sys/module/printk/parameters/ignore_loglevel.
1493
1494 ignore_rlimit_data
1495 Ignore RLIMIT_DATA setting for data mappings,
1496 print warning at first misuse. Can be changed via
1497 /sys/module/kernel/parameters/ignore_rlimit_data.
1498
1499 ihash_entries= [KNL]
1500 Set number of hash buckets for inode cache.
1501
1502 ima_appraise= [IMA] appraise integrity measurements
1503 Format: { "off" | "enforce" | "fix" | "log" }
1504 default: "enforce"
1505
1506 ima_appraise_tcb [IMA]
1507 The builtin appraise policy appraises all files
1508 owned by uid=0.
1509
1510 ima_canonical_fmt [IMA]
1511 Use the canonical format for the binary runtime
1512 measurements, instead of host native format.
1513
1514 ima_hash= [IMA]
1515 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1516 | sha512 | ... }
1517 default: "sha1"
1518
1519 The list of supported hash algorithms is defined
1520 in crypto/hash_info.h.
1521
1522 ima_policy= [IMA]
1523 The builtin policies to load during IMA setup.
1524 Format: "tcb | appraise_tcb | secure_boot |
1525 fail_securely"
1526
1527 The "tcb" policy measures all programs exec'd, files
1528 mmap'd for exec, and all files opened with the read
1529 mode bit set by either the effective uid (euid=0) or
1530 uid=0.
1531
1532 The "appraise_tcb" policy appraises the integrity of
1533 all files owned by root. (This is the equivalent
1534 of ima_appraise_tcb.)
1535
1536 The "secure_boot" policy appraises the integrity
1537 of files (eg. kexec kernel image, kernel modules,
1538 firmware, policy, etc) based on file signatures.
1539
1540 The "fail_securely" policy forces file signature
1541 verification failure also on privileged mounted
1542 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1543 flag.
1544
1545 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1546 Load a policy which meets the needs of the Trusted
1547 Computing Base. This means IMA will measure all
1548 programs exec'd, files mmap'd for exec, and all files
1549 opened for read by uid=0.
1550
1551 ima_template= [IMA]
1552 Select one of defined IMA measurements template formats.
1553 Formats: { "ima" | "ima-ng" | "ima-sig" }
1554 Default: "ima-ng"
1555
1556 ima_template_fmt=
1557 [IMA] Define a custom template format.
1558 Format: { "field1|...|fieldN" }
1559
1560 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1561 Format: <min_file_size>
1562 Set the minimal file size for using asynchronous hash.
1563 If left unspecified, ahash usage is disabled.
1564
1565 ahash performance varies for different data sizes on
1566 different crypto accelerators. This option can be used
1567 to achieve the best performance for a particular HW.
1568
1569 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1570 Format: <bufsize>
1571 Set hashing buffer size. Default: 4k.
1572
1573 ahash performance varies for different chunk sizes on
1574 different crypto accelerators. This option can be used
1575 to achieve best performance for particular HW.
1576
1577 init= [KNL]
1578 Format: <full_path>
1579 Run specified binary instead of /sbin/init as init
1580 process.
1581
1582 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1583 for working out where the kernel is dying during
1584 startup.
1585
1586 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1587 initcall functions. Useful for debugging built-in
1588 modules and initcalls.
1589
1590 initrd= [BOOT] Specify the location of the initial ramdisk
1591
1592 init_pkru= [x86] Specify the default memory protection keys rights
1593 register contents for all processes. 0x55555554 by
1594 default (disallow access to all but pkey 0). Can
1595 override in debugfs after boot.
1596
1597 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1598 Format: <irq>
1599
1600 int_pln_enable [x86] Enable power limit notification interrupt
1601
1602 integrity_audit=[IMA]
1603 Format: { "0" | "1" }
1604 0 -- basic integrity auditing messages. (Default)
1605 1 -- additional integrity auditing messages.
1606
1607 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1608 on
1609 Enable intel iommu driver.
1610 off
1611 Disable intel iommu driver.
1612 igfx_off [Default Off]
1613 By default, gfx is mapped as normal device. If a gfx
1614 device has a dedicated DMAR unit, the DMAR unit is
1615 bypassed by not enabling DMAR with this option. In
1616 this case, gfx device will use physical address for
1617 DMA.
1618 forcedac [x86_64]
1619 With this option iommu will not optimize to look
1620 for io virtual address below 32-bit forcing dual
1621 address cycle on pci bus for cards supporting greater
1622 than 32-bit addressing. The default is to look
1623 for translation below 32-bit and if not available
1624 then look in the higher range.
1625 strict [Default Off]
1626 With this option on every unmap_single operation will
1627 result in a hardware IOTLB flush operation as opposed
1628 to batching them for performance.
1629 sp_off [Default Off]
1630 By default, super page will be supported if Intel IOMMU
1631 has the capability. With this option, super page will
1632 not be supported.
1633 ecs_off [Default Off]
1634 By default, extended context tables will be supported if
1635 the hardware advertises that it has support both for the
1636 extended tables themselves, and also PASID support. With
1637 this option set, extended tables will not be used even
1638 on hardware which claims to support them.
1639 tboot_noforce [Default Off]
1640 Do not force the Intel IOMMU enabled under tboot.
1641 By default, tboot will force Intel IOMMU on, which
1642 could harm performance of some high-throughput
1643 devices like 40GBit network cards, even if identity
1644 mapping is enabled.
1645 Note that using this option lowers the security
1646 provided by tboot because it makes the system
1647 vulnerable to DMA attacks.
1648
1649 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1650 0 disables intel_idle and fall back on acpi_idle.
1651 1 to 9 specify maximum depth of C-state.
1652
1653 intel_pstate= [X86]
1654 disable
1655 Do not enable intel_pstate as the default
1656 scaling driver for the supported processors
1657 passive
1658 Use intel_pstate as a scaling driver, but configure it
1659 to work with generic cpufreq governors (instead of
1660 enabling its internal governor). This mode cannot be
1661 used along with the hardware-managed P-states (HWP)
1662 feature.
1663 force
1664 Enable intel_pstate on systems that prohibit it by default
1665 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1666 instead of acpi-cpufreq may disable platform features, such
1667 as thermal controls and power capping, that rely on ACPI
1668 P-States information being indicated to OSPM and therefore
1669 should be used with caution. This option does not work with
1670 processors that aren't supported by the intel_pstate driver
1671 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1672 no_hwp
1673 Do not enable hardware P state control (HWP)
1674 if available.
1675 hwp_only
1676 Only load intel_pstate on systems which support
1677 hardware P state control (HWP) if available.
1678 support_acpi_ppc
1679 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1680 Description Table, specifies preferred power management
1681 profile as "Enterprise Server" or "Performance Server",
1682 then this feature is turned on by default.
1683 per_cpu_perf_limits
1684 Allow per-logical-CPU P-State performance control limits using
1685 cpufreq sysfs interface
1686
1687 intremap= [X86-64, Intel-IOMMU]
1688 on enable Interrupt Remapping (default)
1689 off disable Interrupt Remapping
1690 nosid disable Source ID checking
1691 no_x2apic_optout
1692 BIOS x2APIC opt-out request will be ignored
1693 nopost disable Interrupt Posting
1694
1695 iomem= Disable strict checking of access to MMIO memory
1696 strict regions from userspace.
1697 relaxed
1698
1699 iommu= [x86]
1700 off
1701 force
1702 noforce
1703 biomerge
1704 panic
1705 nopanic
1706 merge
1707 nomerge
1708 forcesac
1709 soft
1710 pt [x86, IA-64]
1711 nobypass [PPC/POWERNV]
1712 Disable IOMMU bypass, using IOMMU for PCI devices.
1713
1714 iommu.passthrough=
1715 [ARM64] Configure DMA to bypass the IOMMU by default.
1716 Format: { "0" | "1" }
1717 0 - Use IOMMU translation for DMA.
1718 1 - Bypass the IOMMU for DMA.
1719 unset - Use IOMMU translation for DMA.
1720
1721 io7= [HW] IO7 for Marvel based alpha systems
1722 See comment before marvel_specify_io7 in
1723 arch/alpha/kernel/core_marvel.c.
1724
1725 io_delay= [X86] I/O delay method
1726 0x80
1727 Standard port 0x80 based delay
1728 0xed
1729 Alternate port 0xed based delay (needed on some systems)
1730 udelay
1731 Simple two microseconds delay
1732 none
1733 No delay
1734
1735 ip= [IP_PNP]
1736 See Documentation/filesystems/nfs/nfsroot.txt.
1737
1738 irqaffinity= [SMP] Set the default irq affinity mask
1739 The argument is a cpu list, as described above.
1740
1741 irqchip.gicv2_force_probe=
1742 [ARM, ARM64]
1743 Format: <bool>
1744 Force the kernel to look for the second 4kB page
1745 of a GICv2 controller even if the memory range
1746 exposed by the device tree is too small.
1747
1748 irqchip.gicv3_nolpi=
1749 [ARM, ARM64]
1750 Force the kernel to ignore the availability of
1751 LPIs (and by consequence ITSs). Intended for system
1752 that use the kernel as a bootloader, and thus want
1753 to let secondary kernels in charge of setting up
1754 LPIs.
1755
1756 irqfixup [HW]
1757 When an interrupt is not handled search all handlers
1758 for it. Intended to get systems with badly broken
1759 firmware running.
1760
1761 irqpoll [HW]
1762 When an interrupt is not handled search all handlers
1763 for it. Also check all handlers each timer
1764 interrupt. Intended to get systems with badly broken
1765 firmware running.
1766
1767 isapnp= [ISAPNP]
1768 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1769
1770 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
1771 [Deprecated - use cpusets instead]
1772 Format: [flag-list,]<cpu-list>
1773
1774 Specify one or more CPUs to isolate from disturbances
1775 specified in the flag list (default: domain):
1776
1777 nohz
1778 Disable the tick when a single task runs.
1779
1780 A residual 1Hz tick is offloaded to workqueues, which you
1781 need to affine to housekeeping through the global
1782 workqueue's affinity configured via the
1783 /sys/devices/virtual/workqueue/cpumask sysfs file, or
1784 by using the 'domain' flag described below.
1785
1786 NOTE: by default the global workqueue runs on all CPUs,
1787 so to protect individual CPUs the 'cpumask' file has to
1788 be configured manually after bootup.
1789
1790 domain
1791 Isolate from the general SMP balancing and scheduling
1792 algorithms. Note that performing domain isolation this way
1793 is irreversible: it's not possible to bring back a CPU to
1794 the domains once isolated through isolcpus. It's strongly
1795 advised to use cpusets instead to disable scheduler load
1796 balancing through the "cpuset.sched_load_balance" file.
1797 It offers a much more flexible interface where CPUs can
1798 move in and out of an isolated set anytime.
1799
1800 You can move a process onto or off an "isolated" CPU via
1801 the CPU affinity syscalls or cpuset.
1802 <cpu number> begins at 0 and the maximum value is
1803 "number of CPUs in system - 1".
1804
1805 The format of <cpu-list> is described above.
1806
1807
1808
1809 iucv= [HW,NET]
1810
1811 ivrs_ioapic [HW,X86_64]
1812 Provide an override to the IOAPIC-ID<->DEVICE-ID
1813 mapping provided in the IVRS ACPI table. For
1814 example, to map IOAPIC-ID decimal 10 to
1815 PCI device 00:14.0 write the parameter as:
1816 ivrs_ioapic[10]=00:14.0
1817
1818 ivrs_hpet [HW,X86_64]
1819 Provide an override to the HPET-ID<->DEVICE-ID
1820 mapping provided in the IVRS ACPI table. For
1821 example, to map HPET-ID decimal 0 to
1822 PCI device 00:14.0 write the parameter as:
1823 ivrs_hpet[0]=00:14.0
1824
1825 ivrs_acpihid [HW,X86_64]
1826 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1827 mapping provided in the IVRS ACPI table. For
1828 example, to map UART-HID:UID AMD0020:0 to
1829 PCI device 00:14.5 write the parameter as:
1830 ivrs_acpihid[00:14.5]=AMD0020:0
1831
1832 js= [HW,JOY] Analog joystick
1833 See Documentation/input/joydev/joystick.rst.
1834
1835 nokaslr [KNL]
1836 When CONFIG_RANDOMIZE_BASE is set, this disables
1837 kernel and module base offset ASLR (Address Space
1838 Layout Randomization).
1839
1840 kasan_multi_shot
1841 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1842 report on every invalid memory access. Without this
1843 parameter KASAN will print report only for the first
1844 invalid access.
1845
1846 keepinitrd [HW,ARM]
1847
1848 kernelcore= [KNL,X86,IA-64,PPC]
1849 Format: nn[KMGTPE] | nn% | "mirror"
1850 This parameter specifies the amount of memory usable by
1851 the kernel for non-movable allocations. The requested
1852 amount is spread evenly throughout all nodes in the
1853 system as ZONE_NORMAL. The remaining memory is used for
1854 movable memory in its own zone, ZONE_MOVABLE. In the
1855 event, a node is too small to have both ZONE_NORMAL and
1856 ZONE_MOVABLE, kernelcore memory will take priority and
1857 other nodes will have a larger ZONE_MOVABLE.
1858
1859 ZONE_MOVABLE is used for the allocation of pages that
1860 may be reclaimed or moved by the page migration
1861 subsystem. Note that allocations like PTEs-from-HighMem
1862 still use the HighMem zone if it exists, and the Normal
1863 zone if it does not.
1864
1865 It is possible to specify the exact amount of memory in
1866 the form of "nn[KMGTPE]", a percentage of total system
1867 memory in the form of "nn%", or "mirror". If "mirror"
1868 option is specified, mirrored (reliable) memory is used
1869 for non-movable allocations and remaining memory is used
1870 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
1871 are exclusive, so you cannot specify multiple forms.
1872
1873 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1874 Format: <Controller#>[,poll interval]
1875 The controller # is the number of the ehci usb debug
1876 port as it is probed via PCI. The poll interval is
1877 optional and is the number seconds in between
1878 each poll cycle to the debug port in case you need
1879 the functionality for interrupting the kernel with
1880 gdb or control-c on the dbgp connection. When
1881 not using this parameter you use sysrq-g to break into
1882 the kernel debugger.
1883
1884 kgdboc= [KGDB,HW] kgdb over consoles.
1885 Requires a tty driver that supports console polling,
1886 or a supported polling keyboard driver (non-usb).
1887 Serial only format: <serial_device>[,baud]
1888 keyboard only format: kbd
1889 keyboard and serial format: kbd,<serial_device>[,baud]
1890 Optional Kernel mode setting:
1891 kms, kbd format: kms,kbd
1892 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1893
1894 kgdbwait [KGDB] Stop kernel execution and enter the
1895 kernel debugger at the earliest opportunity.
1896
1897 kmac= [MIPS] korina ethernet MAC address.
1898 Configure the RouterBoard 532 series on-chip
1899 Ethernet adapter MAC address.
1900
1901 kmemleak= [KNL] Boot-time kmemleak enable/disable
1902 Valid arguments: on, off
1903 Default: on
1904 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1905 the default is off.
1906
1907 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1908 Default is 0 (don't ignore, but inject #GP)
1909
1910 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
1911 Default is false (don't support).
1912
1913 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1914 KVM MMU at runtime.
1915 Default is 0 (off)
1916
1917 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1918 Default is 1 (enabled)
1919
1920 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1921 for all guests.
1922 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1923
1924 kvm-arm.vgic_v3_group0_trap=
1925 [KVM,ARM] Trap guest accesses to GICv3 group-0
1926 system registers
1927
1928 kvm-arm.vgic_v3_group1_trap=
1929 [KVM,ARM] Trap guest accesses to GICv3 group-1
1930 system registers
1931
1932 kvm-arm.vgic_v3_common_trap=
1933 [KVM,ARM] Trap guest accesses to GICv3 common
1934 system registers
1935
1936 kvm-arm.vgic_v4_enable=
1937 [KVM,ARM] Allow use of GICv4 for direct injection of
1938 LPIs.
1939
1940 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1941 (virtualized MMU) support on capable Intel chips.
1942 Default is 1 (enabled)
1943
1944 kvm-intel.emulate_invalid_guest_state=
1945 [KVM,Intel] Enable emulation of invalid guest states
1946 Default is 0 (disabled)
1947
1948 kvm-intel.flexpriority=
1949 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1950 Default is 1 (enabled)
1951
1952 kvm-intel.nested=
1953 [KVM,Intel] Enable VMX nesting (nVMX).
1954 Default is 0 (disabled)
1955
1956 kvm-intel.unrestricted_guest=
1957 [KVM,Intel] Disable unrestricted guest feature
1958 (virtualized real and unpaged mode) on capable
1959 Intel chips. Default is 1 (enabled)
1960
1961 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1962 feature (tagged TLBs) on capable Intel chips.
1963 Default is 1 (enabled)
1964
1965 l2cr= [PPC]
1966
1967 l3cr= [PPC]
1968
1969 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1970 disabled it.
1971
1972 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1973 value for LAPIC timer one-shot implementation. Default
1974 back to the programmable timer unit in the LAPIC.
1975
1976 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1977 in C2 power state.
1978
1979 libata.dma= [LIBATA] DMA control
1980 libata.dma=0 Disable all PATA and SATA DMA
1981 libata.dma=1 PATA and SATA Disk DMA only
1982 libata.dma=2 ATAPI (CDROM) DMA only
1983 libata.dma=4 Compact Flash DMA only
1984 Combinations also work, so libata.dma=3 enables DMA
1985 for disks and CDROMs, but not CFs.
1986
1987 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1988 libata.ignore_hpa=0 keep BIOS limits (default)
1989 libata.ignore_hpa=1 ignore limits, using full disk
1990
1991 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1992 when set.
1993 Format: <int>
1994
1995 libata.force= [LIBATA] Force configurations. The format is comma
1996 separated list of "[ID:]VAL" where ID is
1997 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1998 matching port, link or device. Basically, it matches
1999 the ATA ID string printed on console by libata. If
2000 the whole ID part is omitted, the last PORT and DEVICE
2001 values are used. If ID hasn't been specified yet, the
2002 configuration applies to all ports, links and devices.
2003
2004 If only DEVICE is omitted, the parameter applies to
2005 the port and all links and devices behind it. DEVICE
2006 number of 0 either selects the first device or the
2007 first fan-out link behind PMP device. It does not
2008 select the host link. DEVICE number of 15 selects the
2009 host link and device attached to it.
2010
2011 The VAL specifies the configuration to force. As long
2012 as there's no ambiguity shortcut notation is allowed.
2013 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2014 The following configurations can be forced.
2015
2016 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2017 Any ID with matching PORT is used.
2018
2019 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2020
2021 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2022 udma[/][16,25,33,44,66,100,133] notation is also
2023 allowed.
2024
2025 * [no]ncq: Turn on or off NCQ.
2026
2027 * [no]ncqtrim: Turn off queued DSM TRIM.
2028
2029 * nohrst, nosrst, norst: suppress hard, soft
2030 and both resets.
2031
2032 * rstonce: only attempt one reset during
2033 hot-unplug link recovery
2034
2035 * dump_id: dump IDENTIFY data.
2036
2037 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2038
2039 * disable: Disable this device.
2040
2041 If there are multiple matching configurations changing
2042 the same attribute, the last one is used.
2043
2044 memblock=debug [KNL] Enable memblock debug messages.
2045
2046 load_ramdisk= [RAM] List of ramdisks to load from floppy
2047 See Documentation/blockdev/ramdisk.txt.
2048
2049 lockd.nlm_grace_period=P [NFS] Assign grace period.
2050 Format: <integer>
2051
2052 lockd.nlm_tcpport=N [NFS] Assign TCP port.
2053 Format: <integer>
2054
2055 lockd.nlm_timeout=T [NFS] Assign timeout value.
2056 Format: <integer>
2057
2058 lockd.nlm_udpport=M [NFS] Assign UDP port.
2059 Format: <integer>
2060
2061 locktorture.nreaders_stress= [KNL]
2062 Set the number of locking read-acquisition kthreads.
2063 Defaults to being automatically set based on the
2064 number of online CPUs.
2065
2066 locktorture.nwriters_stress= [KNL]
2067 Set the number of locking write-acquisition kthreads.
2068
2069 locktorture.onoff_holdoff= [KNL]
2070 Set time (s) after boot for CPU-hotplug testing.
2071
2072 locktorture.onoff_interval= [KNL]
2073 Set time (s) between CPU-hotplug operations, or
2074 zero to disable CPU-hotplug testing.
2075
2076 locktorture.shuffle_interval= [KNL]
2077 Set task-shuffle interval (jiffies). Shuffling
2078 tasks allows some CPUs to go into dyntick-idle
2079 mode during the locktorture test.
2080
2081 locktorture.shutdown_secs= [KNL]
2082 Set time (s) after boot system shutdown. This
2083 is useful for hands-off automated testing.
2084
2085 locktorture.stat_interval= [KNL]
2086 Time (s) between statistics printk()s.
2087
2088 locktorture.stutter= [KNL]
2089 Time (s) to stutter testing, for example,
2090 specifying five seconds causes the test to run for
2091 five seconds, wait for five seconds, and so on.
2092 This tests the locking primitive's ability to
2093 transition abruptly to and from idle.
2094
2095 locktorture.torture_type= [KNL]
2096 Specify the locking implementation to test.
2097
2098 locktorture.verbose= [KNL]
2099 Enable additional printk() statements.
2100
2101 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
2102 Format: <irq>
2103
2104 loglevel= All Kernel Messages with a loglevel smaller than the
2105 console loglevel will be printed to the console. It can
2106 also be changed with klogd or other programs. The
2107 loglevels are defined as follows:
2108
2109 0 (KERN_EMERG) system is unusable
2110 1 (KERN_ALERT) action must be taken immediately
2111 2 (KERN_CRIT) critical conditions
2112 3 (KERN_ERR) error conditions
2113 4 (KERN_WARNING) warning conditions
2114 5 (KERN_NOTICE) normal but significant condition
2115 6 (KERN_INFO) informational
2116 7 (KERN_DEBUG) debug-level messages
2117
2118 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
2119 in bytes. n must be a power of two and greater
2120 than the minimal size. The minimal size is defined
2121 by LOG_BUF_SHIFT kernel config parameter. There is
2122 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2123 that allows to increase the default size depending on
2124 the number of CPUs. See init/Kconfig for more details.
2125
2126 logo.nologo [FB] Disables display of the built-in Linux logo.
2127 This may be used to provide more screen space for
2128 kernel log messages and is useful when debugging
2129 kernel boot problems.
2130
2131 lp=0 [LP] Specify parallel ports to use, e.g,
2132 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
2133 lp=reset first parallel port). 'lp=0' disables the
2134 lp=auto printer driver. 'lp=reset' (which can be
2135 specified in addition to the ports) causes
2136 attached printers to be reset. Using
2137 lp=port1,port2,... specifies the parallel ports
2138 to associate lp devices with, starting with
2139 lp0. A port specification may be 'none' to skip
2140 that lp device, or a parport name such as
2141 'parport0'. Specifying 'lp=auto' instead of a
2142 port specification list means that device IDs
2143 from each port should be examined, to see if
2144 an IEEE 1284-compliant printer is attached; if
2145 so, the driver will manage that printer.
2146 See also header of drivers/char/lp.c.
2147
2148 lpj=n [KNL]
2149 Sets loops_per_jiffy to given constant, thus avoiding
2150 time-consuming boot-time autodetection (up to 250 ms per
2151 CPU). 0 enables autodetection (default). To determine
2152 the correct value for your kernel, boot with normal
2153 autodetection and see what value is printed. Note that
2154 on SMP systems the preset will be applied to all CPUs,
2155 which is likely to cause problems if your CPUs need
2156 significantly divergent settings. An incorrect value
2157 will cause delays in the kernel to be wrong, leading to
2158 unpredictable I/O errors and other breakage. Although
2159 unlikely, in the extreme case this might damage your
2160 hardware.
2161
2162 ltpc= [NET]
2163 Format: <io>,<irq>,<dma>
2164
2165 machvec= [IA-64] Force the use of a particular machine-vector
2166 (machvec) in a generic kernel.
2167 Example: machvec=hpzx1_swiotlb
2168
2169 machtype= [Loongson] Share the same kernel image file between different
2170 yeeloong laptop.
2171 Example: machtype=lemote-yeeloong-2f-7inch
2172
2173 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2174 than or equal to this physical address is ignored.
2175
2176 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2177 will bring up during bootup. maxcpus=n : n >= 0 limits
2178 the kernel to bring up 'n' processors. Surely after
2179 bootup you can bring up the other plugged cpu by executing
2180 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2181 only takes effect during system bootup.
2182 While n=0 is a special case, it is equivalent to "nosmp",
2183 which also disables the IO APIC.
2184
2185 max_loop= [LOOP] The number of loop block devices that get
2186 (loop.max_loop) unconditionally pre-created at init time. The default
2187 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2188 of statically allocating a predefined number, loop
2189 devices can be requested on-demand with the
2190 /dev/loop-control interface.
2191
2192 mce [X86-32] Machine Check Exception
2193
2194 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2195
2196 md= [HW] RAID subsystems devices and level
2197 See Documentation/admin-guide/md.rst.
2198
2199 mdacon= [MDA]
2200 Format: <first>,<last>
2201 Specifies range of consoles to be captured by the MDA.
2202
2203 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2204 Amount of memory to be used when the kernel is not able
2205 to see the whole system memory or for test.
2206 [X86] Work as limiting max address. Use together
2207 with memmap= to avoid physical address space collisions.
2208 Without memmap= PCI devices could be placed at addresses
2209 belonging to unused RAM.
2210
2211 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2212 memory.
2213
2214 memchunk=nn[KMG]
2215 [KNL,SH] Allow user to override the default size for
2216 per-device physically contiguous DMA buffers.
2217
2218 memhp_default_state=online/offline
2219 [KNL] Set the initial state for the memory hotplug
2220 onlining policy. If not specified, the default value is
2221 set according to the
2222 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2223 option.
2224 See Documentation/memory-hotplug.txt.
2225
2226 memmap=exactmap [KNL,X86] Enable setting of an exact
2227 E820 memory map, as specified by the user.
2228 Such memmap=exactmap lines can be constructed based on
2229 BIOS output or other requirements. See the memmap=nn@ss
2230 option description.
2231
2232 memmap=nn[KMG]@ss[KMG]
2233 [KNL] Force usage of a specific region of memory.
2234 Region of memory to be used is from ss to ss+nn.
2235 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2236 which limits max address to nn[KMG].
2237 Multiple different regions can be specified,
2238 comma delimited.
2239 Example:
2240 memmap=100M@2G,100M#3G,1G!1024G
2241
2242 memmap=nn[KMG]#ss[KMG]
2243 [KNL,ACPI] Mark specific memory as ACPI data.
2244 Region of memory to be marked is from ss to ss+nn.
2245
2246 memmap=nn[KMG]$ss[KMG]
2247 [KNL,ACPI] Mark specific memory as reserved.
2248 Region of memory to be reserved is from ss to ss+nn.
2249 Example: Exclude memory from 0x18690000-0x1869ffff
2250 memmap=64K$0x18690000
2251 or
2252 memmap=0x10000$0x18690000
2253 Some bootloaders may need an escape character before '$',
2254 like Grub2, otherwise '$' and the following number
2255 will be eaten.
2256
2257 memmap=nn[KMG]!ss[KMG]
2258 [KNL,X86] Mark specific memory as protected.
2259 Region of memory to be used, from ss to ss+nn.
2260 The memory region may be marked as e820 type 12 (0xc)
2261 and is NVDIMM or ADR memory.
2262
2263 memmap=<size>%<offset>-<oldtype>+<newtype>
2264 [KNL,ACPI] Convert memory within the specified region
2265 from <oldtype> to <newtype>. If "-<oldtype>" is left
2266 out, the whole region will be marked as <newtype>,
2267 even if previously unavailable. If "+<newtype>" is left
2268 out, matching memory will be removed. Types are
2269 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
2270 3 = ACPI, 12 = PRAM.
2271
2272 memory_corruption_check=0/1 [X86]
2273 Some BIOSes seem to corrupt the first 64k of
2274 memory when doing things like suspend/resume.
2275 Setting this option will scan the memory
2276 looking for corruption. Enabling this will
2277 both detect corruption and prevent the kernel
2278 from using the memory being corrupted.
2279 However, its intended as a diagnostic tool; if
2280 repeatable BIOS-originated corruption always
2281 affects the same memory, you can use memmap=
2282 to prevent the kernel from using that memory.
2283
2284 memory_corruption_check_size=size [X86]
2285 By default it checks for corruption in the low
2286 64k, making this memory unavailable for normal
2287 use. Use this parameter to scan for
2288 corruption in more or less memory.
2289
2290 memory_corruption_check_period=seconds [X86]
2291 By default it checks for corruption every 60
2292 seconds. Use this parameter to check at some
2293 other rate. 0 disables periodic checking.
2294
2295 memtest= [KNL,X86,ARM] Enable memtest
2296 Format: <integer>
2297 default : 0 <disable>
2298 Specifies the number of memtest passes to be
2299 performed. Each pass selects another test
2300 pattern from a given set of patterns. Memtest
2301 fills the memory with this pattern, validates
2302 memory contents and reserves bad memory
2303 regions that are detected.
2304
2305 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
2306 Valid arguments: on, off
2307 Default (depends on kernel configuration option):
2308 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2309 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2310 mem_encrypt=on: Activate SME
2311 mem_encrypt=off: Do not activate SME
2312
2313 Refer to Documentation/x86/amd-memory-encryption.txt
2314 for details on when memory encryption can be activated.
2315
2316 mem_sleep_default= [SUSPEND] Default system suspend mode:
2317 s2idle - Suspend-To-Idle
2318 shallow - Power-On Suspend or equivalent (if supported)
2319 deep - Suspend-To-RAM or equivalent (if supported)
2320 See Documentation/admin-guide/pm/sleep-states.rst.
2321
2322 meye.*= [HW] Set MotionEye Camera parameters
2323 See Documentation/media/v4l-drivers/meye.rst.
2324
2325 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2326 Multi-Function General Purpose Timers on AMD Geode
2327 platforms.
2328
2329 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2330 the BIOS has incorrectly applied a workaround. TinyBIOS
2331 version 0.98 is known to be affected, 0.99 fixes the
2332 problem by letting the user disable the workaround.
2333
2334 mga= [HW,DRM]
2335
2336 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2337 physical address is ignored.
2338
2339 mini2440= [ARM,HW,KNL]
2340 Format:[0..2][b][c][t]
2341 Default: "0tb"
2342 MINI2440 configuration specification:
2343 0 - The attached screen is the 3.5" TFT
2344 1 - The attached screen is the 7" TFT
2345 2 - The VGA Shield is attached (1024x768)
2346 Leaving out the screen size parameter will not load
2347 the TFT driver, and the framebuffer will be left
2348 unconfigured.
2349 b - Enable backlight. The TFT backlight pin will be
2350 linked to the kernel VESA blanking code and a GPIO
2351 LED. This parameter is not necessary when using the
2352 VGA shield.
2353 c - Enable the s3c camera interface.
2354 t - Reserved for enabling touchscreen support. The
2355 touchscreen support is not enabled in the mainstream
2356 kernel as of 2.6.30, a preliminary port can be found
2357 in the "bleeding edge" mini2440 support kernel at
2358 http://repo.or.cz/w/linux-2.6/mini2440.git
2359
2360 mminit_loglevel=
2361 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2362 parameter allows control of the logging verbosity for
2363 the additional memory initialisation checks. A value
2364 of 0 disables mminit logging and a level of 4 will
2365 log everything. Information is printed at KERN_DEBUG
2366 so loglevel=8 may also need to be specified.
2367
2368 module.sig_enforce
2369 [KNL] When CONFIG_MODULE_SIG is set, this means that
2370 modules without (valid) signatures will fail to load.
2371 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2372 is always true, so this option does nothing.
2373
2374 module_blacklist= [KNL] Do not load a comma-separated list of
2375 modules. Useful for debugging problem modules.
2376
2377 mousedev.tap_time=
2378 [MOUSE] Maximum time between finger touching and
2379 leaving touchpad surface for touch to be considered
2380 a tap and be reported as a left button click (for
2381 touchpads working in absolute mode only).
2382 Format: <msecs>
2383 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2384 reporting absolute coordinates, such as tablets
2385 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2386 reporting absolute coordinates, such as tablets
2387
2388 movablecore= [KNL,X86,IA-64,PPC]
2389 Format: nn[KMGTPE] | nn%
2390 This parameter is the complement to kernelcore=, it
2391 specifies the amount of memory used for migratable
2392 allocations. If both kernelcore and movablecore is
2393 specified, then kernelcore will be at *least* the
2394 specified value but may be more. If movablecore on its
2395 own is specified, the administrator must be careful
2396 that the amount of memory usable for all allocations
2397 is not too small.
2398
2399 movable_node [KNL] Boot-time switch to make hotplugable memory
2400 NUMA nodes to be movable. This means that the memory
2401 of such nodes will be usable only for movable
2402 allocations which rules out almost all kernel
2403 allocations. Use with caution!
2404
2405 MTD_Partition= [MTD]
2406 Format: <name>,<region-number>,<size>,<offset>
2407
2408 MTD_Region= [MTD] Format:
2409 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2410
2411 mtdparts= [MTD]
2412 See drivers/mtd/cmdlinepart.c.
2413
2414 multitce=off [PPC] This parameter disables the use of the pSeries
2415 firmware feature for updating multiple TCE entries
2416 at a time.
2417
2418 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2419
2420 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2421
2422 boundary - index of last SLC block on Flex-OneNAND.
2423 The remaining blocks are configured as MLC blocks.
2424 lock - Configure if Flex-OneNAND boundary should be locked.
2425 Once locked, the boundary cannot be changed.
2426 1 indicates lock status, 0 indicates unlock status.
2427
2428 mtdset= [ARM]
2429 ARM/S3C2412 JIVE boot control
2430
2431 See arch/arm/mach-s3c2412/mach-jive.c
2432
2433 mtouchusb.raw_coordinates=
2434 [HW] Make the MicroTouch USB driver use raw coordinates
2435 ('y', default) or cooked coordinates ('n')
2436
2437 mtrr_chunk_size=nn[KMG] [X86]
2438 used for mtrr cleanup. It is largest continuous chunk
2439 that could hold holes aka. UC entries.
2440
2441 mtrr_gran_size=nn[KMG] [X86]
2442 Used for mtrr cleanup. It is granularity of mtrr block.
2443 Default is 1.
2444 Large value could prevent small alignment from
2445 using up MTRRs.
2446
2447 mtrr_spare_reg_nr=n [X86]
2448 Format: <integer>
2449 Range: 0,7 : spare reg number
2450 Default : 1
2451 Used for mtrr cleanup. It is spare mtrr entries number.
2452 Set to 2 or more if your graphical card needs more.
2453
2454 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2455
2456 netdev= [NET] Network devices parameters
2457 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2458 Note that mem_start is often overloaded to mean
2459 something different and driver-specific.
2460 This usage is only documented in each driver source
2461 file if at all.
2462
2463 nf_conntrack.acct=
2464 [NETFILTER] Enable connection tracking flow accounting
2465 0 to disable accounting
2466 1 to enable accounting
2467 Default value is 0.
2468
2469 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2470 See Documentation/filesystems/nfs/nfsroot.txt.
2471
2472 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2473 See Documentation/filesystems/nfs/nfsroot.txt.
2474
2475 nfsrootdebug [NFS] enable nfsroot debugging messages.
2476 See Documentation/filesystems/nfs/nfsroot.txt.
2477
2478 nfs.callback_nr_threads=
2479 [NFSv4] set the total number of threads that the
2480 NFS client will assign to service NFSv4 callback
2481 requests.
2482
2483 nfs.callback_tcpport=
2484 [NFS] set the TCP port on which the NFSv4 callback
2485 channel should listen.
2486
2487 nfs.cache_getent=
2488 [NFS] sets the pathname to the program which is used
2489 to update the NFS client cache entries.
2490
2491 nfs.cache_getent_timeout=
2492 [NFS] sets the timeout after which an attempt to
2493 update a cache entry is deemed to have failed.
2494
2495 nfs.idmap_cache_timeout=
2496 [NFS] set the maximum lifetime for idmapper cache
2497 entries.
2498
2499 nfs.enable_ino64=
2500 [NFS] enable 64-bit inode numbers.
2501 If zero, the NFS client will fake up a 32-bit inode
2502 number for the readdir() and stat() syscalls instead
2503 of returning the full 64-bit number.
2504 The default is to return 64-bit inode numbers.
2505
2506 nfs.max_session_cb_slots=
2507 [NFSv4.1] Sets the maximum number of session
2508 slots the client will assign to the callback
2509 channel. This determines the maximum number of
2510 callbacks the client will process in parallel for
2511 a particular server.
2512
2513 nfs.max_session_slots=
2514 [NFSv4.1] Sets the maximum number of session slots
2515 the client will attempt to negotiate with the server.
2516 This limits the number of simultaneous RPC requests
2517 that the client can send to the NFSv4.1 server.
2518 Note that there is little point in setting this
2519 value higher than the max_tcp_slot_table_limit.
2520
2521 nfs.nfs4_disable_idmapping=
2522 [NFSv4] When set to the default of '1', this option
2523 ensures that both the RPC level authentication
2524 scheme and the NFS level operations agree to use
2525 numeric uids/gids if the mount is using the
2526 'sec=sys' security flavour. In effect it is
2527 disabling idmapping, which can make migration from
2528 legacy NFSv2/v3 systems to NFSv4 easier.
2529 Servers that do not support this mode of operation
2530 will be autodetected by the client, and it will fall
2531 back to using the idmapper.
2532 To turn off this behaviour, set the value to '0'.
2533 nfs.nfs4_unique_id=
2534 [NFS4] Specify an additional fixed unique ident-
2535 ification string that NFSv4 clients can insert into
2536 their nfs_client_id4 string. This is typically a
2537 UUID that is generated at system install time.
2538
2539 nfs.send_implementation_id =
2540 [NFSv4.1] Send client implementation identification
2541 information in exchange_id requests.
2542 If zero, no implementation identification information
2543 will be sent.
2544 The default is to send the implementation identification
2545 information.
2546
2547 nfs.recover_lost_locks =
2548 [NFSv4] Attempt to recover locks that were lost due
2549 to a lease timeout on the server. Please note that
2550 doing this risks data corruption, since there are
2551 no guarantees that the file will remain unchanged
2552 after the locks are lost.
2553 If you want to enable the kernel legacy behaviour of
2554 attempting to recover these locks, then set this
2555 parameter to '1'.
2556 The default parameter value of '0' causes the kernel
2557 not to attempt recovery of lost locks.
2558
2559 nfs4.layoutstats_timer =
2560 [NFSv4.2] Change the rate at which the kernel sends
2561 layoutstats to the pNFS metadata server.
2562
2563 Setting this to value to 0 causes the kernel to use
2564 whatever value is the default set by the layout
2565 driver. A non-zero value sets the minimum interval
2566 in seconds between layoutstats transmissions.
2567
2568 nfsd.nfs4_disable_idmapping=
2569 [NFSv4] When set to the default of '1', the NFSv4
2570 server will return only numeric uids and gids to
2571 clients using auth_sys, and will accept numeric uids
2572 and gids from such clients. This is intended to ease
2573 migration from NFSv2/v3.
2574
2575 nmi_debug= [KNL,SH] Specify one or more actions to take
2576 when a NMI is triggered.
2577 Format: [state][,regs][,debounce][,die]
2578
2579 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2580 Format: [panic,][nopanic,][num]
2581 Valid num: 0 or 1
2582 0 - turn hardlockup detector in nmi_watchdog off
2583 1 - turn hardlockup detector in nmi_watchdog on
2584 When panic is specified, panic when an NMI watchdog
2585 timeout occurs (or 'nopanic' to override the opposite
2586 default). To disable both hard and soft lockup detectors,
2587 please see 'nowatchdog'.
2588 This is useful when you use a panic=... timeout and
2589 need the box quickly up again.
2590
2591 These settings can be accessed at runtime via
2592 the nmi_watchdog and hardlockup_panic sysctls.
2593
2594 netpoll.carrier_timeout=
2595 [NET] Specifies amount of time (in seconds) that
2596 netpoll should wait for a carrier. By default netpoll
2597 waits 4 seconds.
2598
2599 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2600 emulation library even if a 387 maths coprocessor
2601 is present.
2602
2603 no_console_suspend
2604 [HW] Never suspend the console
2605 Disable suspending of consoles during suspend and
2606 hibernate operations. Once disabled, debugging
2607 messages can reach various consoles while the rest
2608 of the system is being put to sleep (ie, while
2609 debugging driver suspend/resume hooks). This may
2610 not work reliably with all consoles, but is known
2611 to work with serial and VGA consoles.
2612 To facilitate more flexible debugging, we also add
2613 console_suspend, a printk module parameter to control
2614 it. Users could use console_suspend (usually
2615 /sys/module/printk/parameters/console_suspend) to
2616 turn on/off it dynamically.
2617
2618 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2619 caches in the slab allocator. Saves per-node memory,
2620 but will impact performance.
2621
2622 noalign [KNL,ARM]
2623
2624 noaltinstr [S390] Disables alternative instructions patching
2625 (CPU alternatives feature).
2626
2627 noapic [SMP,APIC] Tells the kernel to not make use of any
2628 IOAPICs that may be present in the system.
2629
2630 noautogroup Disable scheduler automatic task group creation.
2631
2632 nobats [PPC] Do not use BATs for mapping kernel lowmem
2633 on "Classic" PPC cores.
2634
2635 nocache [ARM]
2636
2637 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2638
2639 nodelayacct [KNL] Disable per-task delay accounting
2640
2641 nodsp [SH] Disable hardware DSP at boot time.
2642
2643 noefi Disable EFI runtime services support.
2644
2645 noexec [IA-64]
2646
2647 noexec [X86]
2648 On X86-32 available only on PAE configured kernels.
2649 noexec=on: enable non-executable mappings (default)
2650 noexec=off: disable non-executable mappings
2651
2652 nosmap [X86]
2653 Disable SMAP (Supervisor Mode Access Prevention)
2654 even if it is supported by processor.
2655
2656 nosmep [X86]
2657 Disable SMEP (Supervisor Mode Execution Prevention)
2658 even if it is supported by processor.
2659
2660 noexec32 [X86-64]
2661 This affects only 32-bit executables.
2662 noexec32=on: enable non-executable mappings (default)
2663 read doesn't imply executable mappings
2664 noexec32=off: disable non-executable mappings
2665 read implies executable mappings
2666
2667 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2668
2669 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2670 register save and restore. The kernel will only save
2671 legacy floating-point registers on task switch.
2672
2673 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2674
2675 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2676 Equivalent to smt=1.
2677
2678 nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2
2679 (indirect branch prediction) vulnerability. System may
2680 allow data leaks with this option, which is equivalent
2681 to spectre_v2=off.
2682
2683 nospec_store_bypass_disable
2684 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
2685
2686 noxsave [BUGS=X86] Disables x86 extended register state save
2687 and restore using xsave. The kernel will fallback to
2688 enabling legacy floating-point and sse state.
2689
2690 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2691 register states. The kernel will fall back to use
2692 xsave to save the states. By using this parameter,
2693 performance of saving the states is degraded because
2694 xsave doesn't support modified optimization while
2695 xsaveopt supports it on xsaveopt enabled systems.
2696
2697 noxsaves [X86] Disables xsaves and xrstors used in saving and
2698 restoring x86 extended register state in compacted
2699 form of xsave area. The kernel will fall back to use
2700 xsaveopt and xrstor to save and restore the states
2701 in standard form of xsave area. By using this
2702 parameter, xsave area per process might occupy more
2703 memory on xsaves enabled systems.
2704
2705 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2706 wfi(ARM) instruction doesn't work correctly and not to
2707 use it. This is also useful when using JTAG debugger.
2708
2709 no_file_caps Tells the kernel not to honor file capabilities. The
2710 only way then for a file to be executed with privilege
2711 is to be setuid root or executed by root.
2712
2713 nohalt [IA-64] Tells the kernel not to use the power saving
2714 function PAL_HALT_LIGHT when idle. This increases
2715 power-consumption. On the positive side, it reduces
2716 interrupt wake-up latency, which may improve performance
2717 in certain environments such as networked servers or
2718 real-time systems.
2719
2720 nohibernate [HIBERNATION] Disable hibernation and resume.
2721
2722 nohz= [KNL] Boottime enable/disable dynamic ticks
2723 Valid arguments: on, off
2724 Default: on
2725
2726 nohz_full= [KNL,BOOT,SMP,ISOL]
2727 The argument is a cpu list, as described above.
2728 In kernels built with CONFIG_NO_HZ_FULL=y, set
2729 the specified list of CPUs whose tick will be stopped
2730 whenever possible. The boot CPU will be forced outside
2731 the range to maintain the timekeeping. Any CPUs
2732 in this list will have their RCU callbacks offloaded,
2733 just as if they had also been called out in the
2734 rcu_nocbs= boot parameter.
2735
2736 noiotrap [SH] Disables trapped I/O port accesses.
2737
2738 noirqdebug [X86-32] Disables the code which attempts to detect and
2739 disable unhandled interrupt sources.
2740
2741 no_timer_check [X86,APIC] Disables the code which tests for
2742 broken timer IRQ sources.
2743
2744 noisapnp [ISAPNP] Disables ISA PnP code.
2745
2746 noinitrd [RAM] Tells the kernel not to load any configured
2747 initial RAM disk.
2748
2749 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2750 remapping.
2751 [Deprecated - use intremap=off]
2752
2753 nointroute [IA-64]
2754
2755 noinvpcid [X86] Disable the INVPCID cpu feature.
2756
2757 nojitter [IA-64] Disables jitter checking for ITC timers.
2758
2759 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2760
2761 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2762 fault handling.
2763
2764 no-vmw-sched-clock
2765 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2766 clock and use the default one.
2767
2768 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2769 steal time is computed, but won't influence scheduler
2770 behaviour
2771
2772 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2773
2774 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2775
2776 noltlbs [PPC] Do not use large page/tlb entries for kernel
2777 lowmem mapping on PPC40x and PPC8xx
2778
2779 nomca [IA-64] Disable machine check abort handling
2780
2781 nomce [X86-32] Disable Machine Check Exception
2782
2783 nomfgpt [X86-32] Disable Multi-Function General Purpose
2784 Timer usage (for AMD Geode machines).
2785
2786 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2787 shutdown the other cpus. Instead use the REBOOT_VECTOR
2788 irq.
2789
2790 nomodule Disable module load
2791
2792 nopat [X86] Disable PAT (page attribute table extension of
2793 pagetables) support.
2794
2795 nopcid [X86-64] Disable the PCID cpu feature.
2796
2797 norandmaps Don't use address space randomization. Equivalent to
2798 echo 0 > /proc/sys/kernel/randomize_va_space
2799
2800 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2801 with UP alternatives
2802
2803 nordrand [X86] Disable kernel use of the RDRAND and
2804 RDSEED instructions even if they are supported
2805 by the processor. RDRAND and RDSEED are still
2806 available to user space applications.
2807
2808 noresume [SWSUSP] Disables resume and restores original swap
2809 space.
2810
2811 no-scroll [VGA] Disables scrollback.
2812 This is required for the Braillex ib80-piezo Braille
2813 reader made by F.H. Papenmeier (Germany).
2814
2815 nosbagart [IA-64]
2816
2817 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2818
2819 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2820 and disable the IO APIC. legacy for "maxcpus=0".
2821
2822 nosoftlockup [KNL] Disable the soft-lockup detector.
2823
2824 nosync [HW,M68K] Disables sync negotiation for all devices.
2825
2826 notsc [BUGS=X86-32] Disable Time Stamp Counter
2827
2828 nowatchdog [KNL] Disable both lockup detectors, i.e.
2829 soft-lockup and NMI watchdog (hard-lockup).
2830
2831 nowb [ARM]
2832
2833 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2834
2835 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2836 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2837 Some features depend on CPU0. Known dependencies are:
2838 1. Resume from suspend/hibernate depends on CPU0.
2839 Suspend/hibernate will fail if CPU0 is offline and you
2840 need to online CPU0 before suspend/hibernate.
2841 2. PIC interrupts also depend on CPU0. CPU0 can't be
2842 removed if a PIC interrupt is detected.
2843 It's said poweroff/reboot may depend on CPU0 on some
2844 machines although I haven't seen such issues so far
2845 after CPU0 is offline on a few tested machines.
2846 If the dependencies are under your control, you can
2847 turn on cpu0_hotplug.
2848
2849 nps_mtm_hs_ctr= [KNL,ARC]
2850 This parameter sets the maximum duration, in
2851 cycles, each HW thread of the CTOP can run
2852 without interruptions, before HW switches it.
2853 The actual maximum duration is 16 times this
2854 parameter's value.
2855 Format: integer between 1 and 255
2856 Default: 255
2857
2858 nptcg= [IA-64] Override max number of concurrent global TLB
2859 purges which is reported from either PAL_VM_SUMMARY or
2860 SAL PALO.
2861
2862 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2863 could support. nr_cpus=n : n >= 1 limits the kernel to
2864 support 'n' processors. It could be larger than the
2865 number of already plugged CPU during bootup, later in
2866 runtime you can physically add extra cpu until it reaches
2867 n. So during boot up some boot time memory for per-cpu
2868 variables need be pre-allocated for later physical cpu
2869 hot plugging.
2870
2871 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2872
2873 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2874 Allowed values are enable and disable
2875
2876 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2877 'node', 'default' can be specified
2878 This can be set from sysctl after boot.
2879 See Documentation/sysctl/vm.txt for details.
2880
2881 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2882 See Documentation/debugging-via-ohci1394.txt for more
2883 info.
2884
2885 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2886 Rather than timing out after 20 ms if an EC
2887 command is not properly ACKed, override the length
2888 of the timeout. We have interrupts disabled while
2889 waiting for the ACK, so if this is set too high
2890 interrupts *may* be lost!
2891
2892 omap_mux= [OMAP] Override bootloader pin multiplexing.
2893 Format: <mux_mode0.mode_name=value>...
2894 For example, to override I2C bus2:
2895 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2896
2897 oprofile.timer= [HW]
2898 Use timer interrupt instead of performance counters
2899
2900 oprofile.cpu_type= Force an oprofile cpu type
2901 This might be useful if you have an older oprofile
2902 userland or if you want common events.
2903 Format: { arch_perfmon }
2904 arch_perfmon: [X86] Force use of architectural
2905 perfmon on Intel CPUs instead of the
2906 CPU specific event set.
2907 timer: [X86] Force use of architectural NMI
2908 timer mode (see also oprofile.timer
2909 for generic hr timer mode)
2910
2911 oops=panic Always panic on oopses. Default is to just kill the
2912 process, but there is a small probability of
2913 deadlocking the machine.
2914 This will also cause panics on machine check exceptions.
2915 Useful together with panic=30 to trigger a reboot.
2916
2917 OSS [HW,OSS]
2918 See Documentation/sound/oss/oss-parameters.txt
2919
2920 page_owner= [KNL] Boot-time page_owner enabling option.
2921 Storage of the information about who allocated
2922 each page is disabled in default. With this switch,
2923 we can turn it on.
2924 on: enable the feature
2925
2926 page_poison= [KNL] Boot-time parameter changing the state of
2927 poisoning on the buddy allocator.
2928 off: turn off poisoning
2929 on: turn on poisoning
2930
2931 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2932 timeout > 0: seconds before rebooting
2933 timeout = 0: wait forever
2934 timeout < 0: reboot immediately
2935 Format: <timeout>
2936
2937 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2938 on a WARN().
2939
2940 crash_kexec_post_notifiers
2941 Run kdump after running panic-notifiers and dumping
2942 kmsg. This only for the users who doubt kdump always
2943 succeeds in any situation.
2944 Note that this also increases risks of kdump failure,
2945 because some panic notifiers can make the crashed
2946 kernel more unstable.
2947
2948 parkbd.port= [HW] Parallel port number the keyboard adapter is
2949 connected to, default is 0.
2950 Format: <parport#>
2951 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2952 0 for XT, 1 for AT (default is AT).
2953 Format: <mode>
2954
2955 parport= [HW,PPT] Specify parallel ports. 0 disables.
2956 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2957 Use 'auto' to force the driver to use any
2958 IRQ/DMA settings detected (the default is to
2959 ignore detected IRQ/DMA settings because of
2960 possible conflicts). You can specify the base
2961 address, IRQ, and DMA settings; IRQ and DMA
2962 should be numbers, or 'auto' (for using detected
2963 settings on that particular port), or 'nofifo'
2964 (to avoid using a FIFO even if it is detected).
2965 Parallel ports are assigned in the order they
2966 are specified on the command line, starting
2967 with parport0.
2968
2969 parport_init_mode= [HW,PPT]
2970 Configure VIA parallel port to operate in
2971 a specific mode. This is necessary on Pegasos
2972 computer where firmware has no options for setting
2973 up parallel port mode and sets it to spp.
2974 Currently this function knows 686a and 8231 chips.
2975 Format: [spp|ps2|epp|ecp|ecpepp]
2976
2977 pause_on_oops=
2978 Halt all CPUs after the first oops has been printed for
2979 the specified number of seconds. This is to be used if
2980 your oopses keep scrolling off the screen.
2981
2982 pcbit= [HW,ISDN]
2983
2984 pcd. [PARIDE]
2985 See header of drivers/block/paride/pcd.c.
2986 See also Documentation/blockdev/paride.txt.
2987
2988 pci=option[,option...] [PCI] various PCI subsystem options:
2989 earlydump [X86] dump PCI config space before the kernel
2990 changes anything
2991 off [X86] don't probe for the PCI bus
2992 bios [X86-32] force use of PCI BIOS, don't access
2993 the hardware directly. Use this if your machine
2994 has a non-standard PCI host bridge.
2995 nobios [X86-32] disallow use of PCI BIOS, only direct
2996 hardware access methods are allowed. Use this
2997 if you experience crashes upon bootup and you
2998 suspect they are caused by the BIOS.
2999 conf1 [X86] Force use of PCI Configuration Access
3000 Mechanism 1 (config address in IO port 0xCF8,
3001 data in IO port 0xCFC, both 32-bit).
3002 conf2 [X86] Force use of PCI Configuration Access
3003 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
3004 the function, IO port 0xCFA, also 8-bit, sets
3005 bus number. The config space is then accessed
3006 through ports 0xC000-0xCFFF).
3007 See http://wiki.osdev.org/PCI for more info
3008 on the configuration access mechanisms.
3009 noaer [PCIE] If the PCIEAER kernel config parameter is
3010 enabled, this kernel boot option can be used to
3011 disable the use of PCIE advanced error reporting.
3012 nodomains [PCI] Disable support for multiple PCI
3013 root domains (aka PCI segments, in ACPI-speak).
3014 nommconf [X86] Disable use of MMCONFIG for PCI
3015 Configuration
3016 check_enable_amd_mmconf [X86] check for and enable
3017 properly configured MMIO access to PCI
3018 config space on AMD family 10h CPU
3019 nomsi [MSI] If the PCI_MSI kernel config parameter is
3020 enabled, this kernel boot option can be used to
3021 disable the use of MSI interrupts system-wide.
3022 noioapicquirk [APIC] Disable all boot interrupt quirks.
3023 Safety option to keep boot IRQs enabled. This
3024 should never be necessary.
3025 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
3026 primary IO-APIC for bridges that cannot disable
3027 boot IRQs. This fixes a source of spurious IRQs
3028 when the system masks IRQs.
3029 noioapicreroute [APIC] Disable workaround that uses the
3030 boot IRQ equivalent of an IRQ that connects to
3031 a chipset where boot IRQs cannot be disabled.
3032 The opposite of ioapicreroute.
3033 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
3034 routing table. These calls are known to be buggy
3035 on several machines and they hang the machine
3036 when used, but on other computers it's the only
3037 way to get the interrupt routing table. Try
3038 this option if the kernel is unable to allocate
3039 IRQs or discover secondary PCI buses on your
3040 motherboard.
3041 rom [X86] Assign address space to expansion ROMs.
3042 Use with caution as certain devices share
3043 address decoders between ROMs and other
3044 resources.
3045 norom [X86] Do not assign address space to
3046 expansion ROMs that do not already have
3047 BIOS assigned address ranges.
3048 nobar [X86] Do not assign address space to the
3049 BARs that weren't assigned by the BIOS.
3050 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
3051 assigned automatically to PCI devices. You can
3052 make the kernel exclude IRQs of your ISA cards
3053 this way.
3054 pirqaddr=0xAAAAA [X86] Specify the physical address
3055 of the PIRQ table (normally generated
3056 by the BIOS) if it is outside the
3057 F0000h-100000h range.
3058 lastbus=N [X86] Scan all buses thru bus #N. Can be
3059 useful if the kernel is unable to find your
3060 secondary buses and you want to tell it
3061 explicitly which ones they are.
3062 assign-busses [X86] Always assign all PCI bus
3063 numbers ourselves, overriding
3064 whatever the firmware may have done.
3065 usepirqmask [X86] Honor the possible IRQ mask stored
3066 in the BIOS $PIR table. This is needed on
3067 some systems with broken BIOSes, notably
3068 some HP Pavilion N5400 and Omnibook XE3
3069 notebooks. This will have no effect if ACPI
3070 IRQ routing is enabled.
3071 noacpi [X86] Do not use ACPI for IRQ routing
3072 or for PCI scanning.
3073 use_crs [X86] Use PCI host bridge window information
3074 from ACPI. On BIOSes from 2008 or later, this
3075 is enabled by default. If you need to use this,
3076 please report a bug.
3077 nocrs [X86] Ignore PCI host bridge windows from ACPI.
3078 If you need to use this, please report a bug.
3079 routeirq Do IRQ routing for all PCI devices.
3080 This is normally done in pci_enable_device(),
3081 so this option is a temporary workaround
3082 for broken drivers that don't call it.
3083 skip_isa_align [X86] do not align io start addr, so can
3084 handle more pci cards
3085 noearly [X86] Don't do any early type 1 scanning.
3086 This might help on some broken boards which
3087 machine check when some devices' config space
3088 is read. But various workarounds are disabled
3089 and some IOMMU drivers will not work.
3090 bfsort Sort PCI devices into breadth-first order.
3091 This sorting is done to get a device
3092 order compatible with older (<= 2.4) kernels.
3093 nobfsort Don't sort PCI devices into breadth-first order.
3094 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
3095 tuning and use the BIOS-configured MPS defaults.
3096 pcie_bus_safe Set every device's MPS to the largest value
3097 supported by all devices below the root complex.
3098 pcie_bus_perf Set device MPS to the largest allowable MPS
3099 based on its parent bus. Also set MRRS (Max
3100 Read Request Size) to the largest supported
3101 value (no larger than the MPS that the device
3102 or bus can support) for best performance.
3103 pcie_bus_peer2peer Set every device's MPS to 128B, which
3104 every device is guaranteed to support. This
3105 configuration allows peer-to-peer DMA between
3106 any pair of devices, possibly at the cost of
3107 reduced performance. This also guarantees
3108 that hot-added devices will work.
3109 cbiosize=nn[KMG] The fixed amount of bus space which is
3110 reserved for the CardBus bridge's IO window.
3111 The default value is 256 bytes.
3112 cbmemsize=nn[KMG] The fixed amount of bus space which is
3113 reserved for the CardBus bridge's memory
3114 window. The default value is 64 megabytes.
3115 resource_alignment=
3116 Format:
3117 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3118 [<order of align>@]pci:<vendor>:<device>\
3119 [:<subvendor>:<subdevice>][; ...]
3120 Specifies alignment and device to reassign
3121 aligned memory resources.
3122 If <order of align> is not specified,
3123 PAGE_SIZE is used as alignment.
3124 PCI-PCI bridge can be specified, if resource
3125 windows need to be expanded.
3126 To specify the alignment for several
3127 instances of a device, the PCI vendor,
3128 device, subvendor, and subdevice may be
3129 specified, e.g., 4096@pci:8086:9c22:103c:198f
3130 ecrc= Enable/disable PCIe ECRC (transaction layer
3131 end-to-end CRC checking).
3132 bios: Use BIOS/firmware settings. This is the
3133 the default.
3134 off: Turn ECRC off
3135 on: Turn ECRC on.
3136 hpiosize=nn[KMG] The fixed amount of bus space which is
3137 reserved for hotplug bridge's IO window.
3138 Default size is 256 bytes.
3139 hpmemsize=nn[KMG] The fixed amount of bus space which is
3140 reserved for hotplug bridge's memory window.
3141 Default size is 2 megabytes.
3142 hpbussize=nn The minimum amount of additional bus numbers
3143 reserved for buses below a hotplug bridge.
3144 Default is 1.
3145 realloc= Enable/disable reallocating PCI bridge resources
3146 if allocations done by BIOS are too small to
3147 accommodate resources required by all child
3148 devices.
3149 off: Turn realloc off
3150 on: Turn realloc on
3151 realloc same as realloc=on
3152 noari do not use PCIe ARI.
3153 pcie_scan_all Scan all possible PCIe devices. Otherwise we
3154 only look for one device below a PCIe downstream
3155 port.
3156 big_root_window Try to add a big 64bit memory window to the PCIe
3157 root complex on AMD CPUs. Some GFX hardware
3158 can resize a BAR to allow access to all VRAM.
3159 Adding the window is slightly risky (it may
3160 conflict with unreported devices), so this
3161 taints the kernel.
3162
3163 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
3164 Management.
3165 off Disable ASPM.
3166 force Enable ASPM even on devices that claim not to support it.
3167 WARNING: Forcing ASPM on may cause system lockups.
3168
3169 pcie_ports= [PCIE] PCIe port services handling:
3170 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
3171 even if the platform doesn't give the OS permission to
3172 use them. This may cause conflicts if the platform
3173 also tries to use these services.
3174 compat Disable native PCIe services (PME, AER, DPC, PCIe
3175 hotplug).
3176
3177 pcie_port_pm= [PCIE] PCIe port power management handling:
3178 off Disable power management of all PCIe ports
3179 force Forcibly enable power management of all PCIe ports
3180
3181 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
3182 nomsi Do not use MSI for native PCIe PME signaling (this makes
3183 all PCIe root ports use INTx for all services).
3184
3185 pcmv= [HW,PCMCIA] BadgePAD 4
3186
3187 pd_ignore_unused
3188 [PM]
3189 Keep all power-domains already enabled by bootloader on,
3190 even if no driver has claimed them. This is useful
3191 for debug and development, but should not be
3192 needed on a platform with proper driver support.
3193
3194 pd. [PARIDE]
3195 See Documentation/blockdev/paride.txt.
3196
3197 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3198 boot time.
3199 Format: { 0 | 1 }
3200 See arch/parisc/kernel/pdc_chassis.c
3201
3202 percpu_alloc= Select which percpu first chunk allocator to use.
3203 Currently supported values are "embed" and "page".
3204 Archs may support subset or none of the selections.
3205 See comments in mm/percpu.c for details on each
3206 allocator. This parameter is primarily for debugging
3207 and performance comparison.
3208
3209 pf. [PARIDE]
3210 See Documentation/blockdev/paride.txt.
3211
3212 pg. [PARIDE]
3213 See Documentation/blockdev/paride.txt.
3214
3215 pirq= [SMP,APIC] Manual mp-table setup
3216 See Documentation/x86/i386/IO-APIC.txt.
3217
3218 plip= [PPT,NET] Parallel port network link
3219 Format: { parport<nr> | timid | 0 }
3220 See also Documentation/admin-guide/parport.rst.
3221
3222 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3223 Override pmtimer IOPort with a hex value.
3224 e.g. pmtmr=0x508
3225
3226 pnp.debug=1 [PNP]
3227 Enable PNP debug messages (depends on the
3228 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3229 via /sys/module/pnp/parameters/debug. We always show
3230 current resource usage; turning this on also shows
3231 possible settings and some assignment information.
3232
3233 pnpacpi= [ACPI]
3234 { off }
3235
3236 pnpbios= [ISAPNP]
3237 { on | off | curr | res | no-curr | no-res }
3238
3239 pnp_reserve_irq=
3240 [ISAPNP] Exclude IRQs for the autoconfiguration
3241
3242 pnp_reserve_dma=
3243 [ISAPNP] Exclude DMAs for the autoconfiguration
3244
3245 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3246 Ranges are in pairs (I/O port base and size).
3247
3248 pnp_reserve_mem=
3249 [ISAPNP] Exclude memory regions for the
3250 autoconfiguration.
3251 Ranges are in pairs (memory base and size).
3252
3253 ports= [IP_VS_FTP] IPVS ftp helper module
3254 Default is 21.
3255 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3256 may be specified.
3257 Format: <port>,<port>....
3258
3259 powersave=off [PPC] This option disables power saving features.
3260 It specifically disables cpuidle and sets the
3261 platform machine description specific power_save
3262 function to NULL. On Idle the CPU just reduces
3263 execution priority.
3264
3265 ppc_strict_facility_enable
3266 [PPC] This option catches any kernel floating point,
3267 Altivec, VSX and SPE outside of regions specifically
3268 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3269 There is some performance impact when enabling this.
3270
3271 ppc_tm= [PPC]
3272 Format: {"off"}
3273 Disable Hardware Transactional Memory
3274
3275 print-fatal-signals=
3276 [KNL] debug: print fatal signals
3277
3278 If enabled, warn about various signal handling
3279 related application anomalies: too many signals,
3280 too many POSIX.1 timers, fatal signals causing a
3281 coredump - etc.
3282
3283 If you hit the warning due to signal overflow,
3284 you might want to try "ulimit -i unlimited".
3285
3286 default: off.
3287
3288 printk.always_kmsg_dump=
3289 Trigger kmsg_dump for cases other than kernel oops or
3290 panics
3291 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3292 default: disabled
3293
3294 printk.devkmsg={on,off,ratelimit}
3295 Control writing to /dev/kmsg.
3296 on - unlimited logging to /dev/kmsg from userspace
3297 off - logging to /dev/kmsg disabled
3298 ratelimit - ratelimit the logging
3299 Default: ratelimit
3300
3301 printk.time= Show timing data prefixed to each printk message line
3302 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3303
3304 processor.max_cstate= [HW,ACPI]
3305 Limit processor to maximum C-state
3306 max_cstate=9 overrides any DMI blacklist limit.
3307
3308 processor.nocst [HW,ACPI]
3309 Ignore the _CST method to determine C-states,
3310 instead using the legacy FADT method
3311
3312 profile= [KNL] Enable kernel profiling via /proc/profile
3313 Format: [<profiletype>,]<number>
3314 Param: <profiletype>: "schedule", "sleep", or "kvm"
3315 [defaults to kernel profiling]
3316 Param: "schedule" - profile schedule points.
3317 Param: "sleep" - profile D-state sleeping (millisecs).
3318 Requires CONFIG_SCHEDSTATS
3319 Param: "kvm" - profile VM exits.
3320 Param: <number> - step/bucket size as a power of 2 for
3321 statistical time based profiling.
3322
3323 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3324 before loading.
3325 See Documentation/blockdev/ramdisk.txt.
3326
3327 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3328 probe for; one of (bare|imps|exps|lifebook|any).
3329 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3330 per second.
3331 psmouse.resetafter= [HW,MOUSE]
3332 Try to reset the device after so many bad packets
3333 (0 = never).
3334 psmouse.resolution=
3335 [HW,MOUSE] Set desired mouse resolution, in dpi.
3336 psmouse.smartscroll=
3337 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3338 0 = disabled, 1 = enabled (default).
3339
3340 pstore.backend= Specify the name of the pstore backend to use
3341
3342 pt. [PARIDE]
3343 See Documentation/blockdev/paride.txt.
3344
3345 pti= [X86_64] Control Page Table Isolation of user and
3346 kernel address spaces. Disabling this feature
3347 removes hardening, but improves performance of
3348 system calls and interrupts.
3349
3350 on - unconditionally enable
3351 off - unconditionally disable
3352 auto - kernel detects whether your CPU model is
3353 vulnerable to issues that PTI mitigates
3354
3355 Not specifying this option is equivalent to pti=auto.
3356
3357 nopti [X86_64]
3358 Equivalent to pti=off
3359
3360 pty.legacy_count=
3361 [KNL] Number of legacy pty's. Overwrites compiled-in
3362 default number.
3363
3364 quiet [KNL] Disable most log messages
3365
3366 r128= [HW,DRM]
3367
3368 raid= [HW,RAID]
3369 See Documentation/admin-guide/md.rst.
3370
3371 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3372 See Documentation/blockdev/ramdisk.txt.
3373
3374 ras=option[,option,...] [KNL] RAS-specific options
3375
3376 cec_disable [X86]
3377 Disable the Correctable Errors Collector,
3378 see CONFIG_RAS_CEC help text.
3379
3380 rcu_nocbs= [KNL]
3381 The argument is a cpu list, as described above.
3382
3383 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3384 the specified list of CPUs to be no-callback CPUs.
3385 Invocation of these CPUs' RCU callbacks will
3386 be offloaded to "rcuox/N" kthreads created for
3387 that purpose, where "x" is "b" for RCU-bh, "p"
3388 for RCU-preempt, and "s" for RCU-sched, and "N"
3389 is the CPU number. This reduces OS jitter on the
3390 offloaded CPUs, which can be useful for HPC and
3391 real-time workloads. It can also improve energy
3392 efficiency for asymmetric multiprocessors.
3393
3394 rcu_nocb_poll [KNL]
3395 Rather than requiring that offloaded CPUs
3396 (specified by rcu_nocbs= above) explicitly
3397 awaken the corresponding "rcuoN" kthreads,
3398 make these kthreads poll for callbacks.
3399 This improves the real-time response for the
3400 offloaded CPUs by relieving them of the need to
3401 wake up the corresponding kthread, but degrades
3402 energy efficiency by requiring that the kthreads
3403 periodically wake up to do the polling.
3404
3405 rcutree.blimit= [KNL]
3406 Set maximum number of finished RCU callbacks to
3407 process in one batch.
3408
3409 rcutree.dump_tree= [KNL]
3410 Dump the structure of the rcu_node combining tree
3411 out at early boot. This is used for diagnostic
3412 purposes, to verify correct tree setup.
3413
3414 rcutree.gp_cleanup_delay= [KNL]
3415 Set the number of jiffies to delay each step of
3416 RCU grace-period cleanup.
3417
3418 rcutree.gp_init_delay= [KNL]
3419 Set the number of jiffies to delay each step of
3420 RCU grace-period initialization.
3421
3422 rcutree.gp_preinit_delay= [KNL]
3423 Set the number of jiffies to delay each step of
3424 RCU grace-period pre-initialization, that is,
3425 the propagation of recent CPU-hotplug changes up
3426 the rcu_node combining tree.
3427
3428 rcutree.rcu_fanout_exact= [KNL]
3429 Disable autobalancing of the rcu_node combining
3430 tree. This is used by rcutorture, and might
3431 possibly be useful for architectures having high
3432 cache-to-cache transfer latencies.
3433
3434 rcutree.rcu_fanout_leaf= [KNL]
3435 Change the number of CPUs assigned to each
3436 leaf rcu_node structure. Useful for very
3437 large systems, which will choose the value 64,
3438 and for NUMA systems with large remote-access
3439 latencies, which will choose a value aligned
3440 with the appropriate hardware boundaries.
3441
3442 rcutree.jiffies_till_sched_qs= [KNL]
3443 Set required age in jiffies for a
3444 given grace period before RCU starts
3445 soliciting quiescent-state help from
3446 rcu_note_context_switch().
3447
3448 rcutree.jiffies_till_first_fqs= [KNL]
3449 Set delay from grace-period initialization to
3450 first attempt to force quiescent states.
3451 Units are jiffies, minimum value is zero,
3452 and maximum value is HZ.
3453
3454 rcutree.jiffies_till_next_fqs= [KNL]
3455 Set delay between subsequent attempts to force
3456 quiescent states. Units are jiffies, minimum
3457 value is one, and maximum value is HZ.
3458
3459 rcutree.kthread_prio= [KNL,BOOT]
3460 Set the SCHED_FIFO priority of the RCU per-CPU
3461 kthreads (rcuc/N). This value is also used for
3462 the priority of the RCU boost threads (rcub/N)
3463 and for the RCU grace-period kthreads (rcu_bh,
3464 rcu_preempt, and rcu_sched). If RCU_BOOST is
3465 set, valid values are 1-99 and the default is 1
3466 (the least-favored priority). Otherwise, when
3467 RCU_BOOST is not set, valid values are 0-99 and
3468 the default is zero (non-realtime operation).
3469
3470 rcutree.rcu_nocb_leader_stride= [KNL]
3471 Set the number of NOCB kthread groups, which
3472 defaults to the square root of the number of
3473 CPUs. Larger numbers reduces the wakeup overhead
3474 on the per-CPU grace-period kthreads, but increases
3475 that same overhead on each group's leader.
3476
3477 rcutree.qhimark= [KNL]
3478 Set threshold of queued RCU callbacks beyond which
3479 batch limiting is disabled.
3480
3481 rcutree.qlowmark= [KNL]
3482 Set threshold of queued RCU callbacks below which
3483 batch limiting is re-enabled.
3484
3485 rcutree.rcu_idle_gp_delay= [KNL]
3486 Set wakeup interval for idle CPUs that have
3487 RCU callbacks (RCU_FAST_NO_HZ=y).
3488
3489 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3490 Set wakeup interval for idle CPUs that have
3491 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3492 Lazy RCU callbacks are those which RCU can
3493 prove do nothing more than free memory.
3494
3495 rcutree.rcu_kick_kthreads= [KNL]
3496 Cause the grace-period kthread to get an extra
3497 wake_up() if it sleeps three times longer than
3498 it should at force-quiescent-state time.
3499 This wake_up() will be accompanied by a
3500 WARN_ONCE() splat and an ftrace_dump().
3501
3502 rcuperf.gp_async= [KNL]
3503 Measure performance of asynchronous
3504 grace-period primitives such as call_rcu().
3505
3506 rcuperf.gp_async_max= [KNL]
3507 Specify the maximum number of outstanding
3508 callbacks per writer thread. When a writer
3509 thread exceeds this limit, it invokes the
3510 corresponding flavor of rcu_barrier() to allow
3511 previously posted callbacks to drain.
3512
3513 rcuperf.gp_exp= [KNL]
3514 Measure performance of expedited synchronous
3515 grace-period primitives.
3516
3517 rcuperf.holdoff= [KNL]
3518 Set test-start holdoff period. The purpose of
3519 this parameter is to delay the start of the
3520 test until boot completes in order to avoid
3521 interference.
3522
3523 rcuperf.nreaders= [KNL]
3524 Set number of RCU readers. The value -1 selects
3525 N, where N is the number of CPUs. A value
3526 "n" less than -1 selects N-n+1, where N is again
3527 the number of CPUs. For example, -2 selects N
3528 (the number of CPUs), -3 selects N+1, and so on.
3529 A value of "n" less than or equal to -N selects
3530 a single reader.
3531
3532 rcuperf.nwriters= [KNL]
3533 Set number of RCU writers. The values operate
3534 the same as for rcuperf.nreaders.
3535 N, where N is the number of CPUs
3536
3537 rcuperf.perf_type= [KNL]
3538 Specify the RCU implementation to test.
3539
3540 rcuperf.shutdown= [KNL]
3541 Shut the system down after performance tests
3542 complete. This is useful for hands-off automated
3543 testing.
3544
3545 rcuperf.verbose= [KNL]
3546 Enable additional printk() statements.
3547
3548 rcuperf.writer_holdoff= [KNL]
3549 Write-side holdoff between grace periods,
3550 in microseconds. The default of zero says
3551 no holdoff.
3552
3553 rcutorture.cbflood_inter_holdoff= [KNL]
3554 Set holdoff time (jiffies) between successive
3555 callback-flood tests.
3556
3557 rcutorture.cbflood_intra_holdoff= [KNL]
3558 Set holdoff time (jiffies) between successive
3559 bursts of callbacks within a given callback-flood
3560 test.
3561
3562 rcutorture.cbflood_n_burst= [KNL]
3563 Set the number of bursts making up a given
3564 callback-flood test. Set this to zero to
3565 disable callback-flood testing.
3566
3567 rcutorture.cbflood_n_per_burst= [KNL]
3568 Set the number of callbacks to be registered
3569 in a given burst of a callback-flood test.
3570
3571 rcutorture.fqs_duration= [KNL]
3572 Set duration of force_quiescent_state bursts
3573 in microseconds.
3574
3575 rcutorture.fqs_holdoff= [KNL]
3576 Set holdoff time within force_quiescent_state bursts
3577 in microseconds.
3578
3579 rcutorture.fqs_stutter= [KNL]
3580 Set wait time between force_quiescent_state bursts
3581 in seconds.
3582
3583 rcutorture.gp_cond= [KNL]
3584 Use conditional/asynchronous update-side
3585 primitives, if available.
3586
3587 rcutorture.gp_exp= [KNL]
3588 Use expedited update-side primitives, if available.
3589
3590 rcutorture.gp_normal= [KNL]
3591 Use normal (non-expedited) asynchronous
3592 update-side primitives, if available.
3593
3594 rcutorture.gp_sync= [KNL]
3595 Use normal (non-expedited) synchronous
3596 update-side primitives, if available. If all
3597 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3598 rcutorture.gp_normal=, and rcutorture.gp_sync=
3599 are zero, rcutorture acts as if is interpreted
3600 they are all non-zero.
3601
3602 rcutorture.n_barrier_cbs= [KNL]
3603 Set callbacks/threads for rcu_barrier() testing.
3604
3605 rcutorture.nfakewriters= [KNL]
3606 Set number of concurrent RCU writers. These just
3607 stress RCU, they don't participate in the actual
3608 test, hence the "fake".
3609
3610 rcutorture.nreaders= [KNL]
3611 Set number of RCU readers. The value -1 selects
3612 N-1, where N is the number of CPUs. A value
3613 "n" less than -1 selects N-n-2, where N is again
3614 the number of CPUs. For example, -2 selects N
3615 (the number of CPUs), -3 selects N+1, and so on.
3616
3617 rcutorture.object_debug= [KNL]
3618 Enable debug-object double-call_rcu() testing.
3619
3620 rcutorture.onoff_holdoff= [KNL]
3621 Set time (s) after boot for CPU-hotplug testing.
3622
3623 rcutorture.onoff_interval= [KNL]
3624 Set time (s) between CPU-hotplug operations, or
3625 zero to disable CPU-hotplug testing.
3626
3627 rcutorture.shuffle_interval= [KNL]
3628 Set task-shuffle interval (s). Shuffling tasks
3629 allows some CPUs to go into dyntick-idle mode
3630 during the rcutorture test.
3631
3632 rcutorture.shutdown_secs= [KNL]
3633 Set time (s) after boot system shutdown. This
3634 is useful for hands-off automated testing.
3635
3636 rcutorture.stall_cpu= [KNL]
3637 Duration of CPU stall (s) to test RCU CPU stall
3638 warnings, zero to disable.
3639
3640 rcutorture.stall_cpu_holdoff= [KNL]
3641 Time to wait (s) after boot before inducing stall.
3642
3643 rcutorture.stall_cpu_irqsoff= [KNL]
3644 Disable interrupts while stalling if set.
3645
3646 rcutorture.stat_interval= [KNL]
3647 Time (s) between statistics printk()s.
3648
3649 rcutorture.stutter= [KNL]
3650 Time (s) to stutter testing, for example, specifying
3651 five seconds causes the test to run for five seconds,
3652 wait for five seconds, and so on. This tests RCU's
3653 ability to transition abruptly to and from idle.
3654
3655 rcutorture.test_boost= [KNL]
3656 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3657 "Maybe" means test if the RCU implementation
3658 under test support RCU priority boosting.
3659
3660 rcutorture.test_boost_duration= [KNL]
3661 Duration (s) of each individual boost test.
3662
3663 rcutorture.test_boost_interval= [KNL]
3664 Interval (s) between each boost test.
3665
3666 rcutorture.test_no_idle_hz= [KNL]
3667 Test RCU's dyntick-idle handling. See also the
3668 rcutorture.shuffle_interval parameter.
3669
3670 rcutorture.torture_type= [KNL]
3671 Specify the RCU implementation to test.
3672
3673 rcutorture.verbose= [KNL]
3674 Enable additional printk() statements.
3675
3676 rcupdate.rcu_cpu_stall_suppress= [KNL]
3677 Suppress RCU CPU stall warning messages.
3678
3679 rcupdate.rcu_cpu_stall_timeout= [KNL]
3680 Set timeout for RCU CPU stall warning messages.
3681
3682 rcupdate.rcu_expedited= [KNL]
3683 Use expedited grace-period primitives, for
3684 example, synchronize_rcu_expedited() instead
3685 of synchronize_rcu(). This reduces latency,
3686 but can increase CPU utilization, degrade
3687 real-time latency, and degrade energy efficiency.
3688 No effect on CONFIG_TINY_RCU kernels.
3689
3690 rcupdate.rcu_normal= [KNL]
3691 Use only normal grace-period primitives,
3692 for example, synchronize_rcu() instead of
3693 synchronize_rcu_expedited(). This improves
3694 real-time latency, CPU utilization, and
3695 energy efficiency, but can expose users to
3696 increased grace-period latency. This parameter
3697 overrides rcupdate.rcu_expedited. No effect on
3698 CONFIG_TINY_RCU kernels.
3699
3700 rcupdate.rcu_normal_after_boot= [KNL]
3701 Once boot has completed (that is, after
3702 rcu_end_inkernel_boot() has been invoked), use
3703 only normal grace-period primitives. No effect
3704 on CONFIG_TINY_RCU kernels.
3705
3706 rcupdate.rcu_task_stall_timeout= [KNL]
3707 Set timeout in jiffies for RCU task stall warning
3708 messages. Disable with a value less than or equal
3709 to zero.
3710
3711 rcupdate.rcu_self_test= [KNL]
3712 Run the RCU early boot self tests
3713
3714 rcupdate.rcu_self_test_bh= [KNL]
3715 Run the RCU bh early boot self tests
3716
3717 rcupdate.rcu_self_test_sched= [KNL]
3718 Run the RCU sched early boot self tests
3719
3720 rdinit= [KNL]
3721 Format: <full_path>
3722 Run specified binary instead of /init from the ramdisk,
3723 used for early userspace startup. See initrd.
3724
3725 rdt= [HW,X86,RDT]
3726 Turn on/off individual RDT features. List is:
3727 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
3728 mba.
3729 E.g. to turn on cmt and turn off mba use:
3730 rdt=cmt,!mba
3731
3732 reboot= [KNL]
3733 Format (x86 or x86_64):
3734 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3735 [[,]s[mp]#### \
3736 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3737 [[,]f[orce]
3738 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3739 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3740 reboot_force is either force or not specified,
3741 reboot_cpu is s[mp]#### with #### being the processor
3742 to be used for rebooting.
3743
3744 relax_domain_level=
3745 [KNL, SMP] Set scheduler's default relax_domain_level.
3746 See Documentation/cgroup-v1/cpusets.txt.
3747
3748 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
3749 Format: <base1>,<size1>[,<base2>,<size2>,...]
3750 Reserve I/O ports or memory so the kernel won't use
3751 them. If <base> is less than 0x10000, the region
3752 is assumed to be I/O ports; otherwise it is memory.
3753
3754 reservetop= [X86-32]
3755 Format: nn[KMG]
3756 Reserves a hole at the top of the kernel virtual
3757 address space.
3758
3759 reservelow= [X86]
3760 Format: nn[K]
3761 Set the amount of memory to reserve for BIOS at
3762 the bottom of the address space.
3763
3764 reset_devices [KNL] Force drivers to reset the underlying device
3765 during initialization.
3766
3767 resume= [SWSUSP]
3768 Specify the partition device for software suspend
3769 Format:
3770 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3771
3772 resume_offset= [SWSUSP]
3773 Specify the offset from the beginning of the partition
3774 given by "resume=" at which the swap header is located,
3775 in <PAGE_SIZE> units (needed only for swap files).
3776 See Documentation/power/swsusp-and-swap-files.txt
3777
3778 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3779 read the resume files
3780
3781 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3782 Useful for devices that are detected asynchronously
3783 (e.g. USB and MMC devices).
3784
3785 hibernate= [HIBERNATION]
3786 noresume Don't check if there's a hibernation image
3787 present during boot.
3788 nocompress Don't compress/decompress hibernation images.
3789 no Disable hibernation and resume.
3790 protect_image Turn on image protection during restoration
3791 (that will set all pages holding image data
3792 during restoration read-only).
3793
3794 retain_initrd [RAM] Keep initrd memory after extraction
3795
3796 rfkill.default_state=
3797 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3798 etc. communication is blocked by default.
3799 1 Unblocked.
3800
3801 rfkill.master_switch_mode=
3802 0 The "airplane mode" button does nothing.
3803 1 The "airplane mode" button toggles between everything
3804 blocked and the previous configuration.
3805 2 The "airplane mode" button toggles between everything
3806 blocked and everything unblocked.
3807
3808 rhash_entries= [KNL,NET]
3809 Set number of hash buckets for route cache
3810
3811 ring3mwait=disable
3812 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
3813 CPUs.
3814
3815 ro [KNL] Mount root device read-only on boot
3816
3817 rodata= [KNL]
3818 on Mark read-only kernel memory as read-only (default).
3819 off Leave read-only kernel memory writable for debugging.
3820
3821 rockchip.usb_uart
3822 Enable the uart passthrough on the designated usb port
3823 on Rockchip SoCs. When active, the signals of the
3824 debug-uart get routed to the D+ and D- pins of the usb
3825 port and the regular usb controller gets disabled.
3826
3827 root= [KNL] Root filesystem
3828 See name_to_dev_t comment in init/do_mounts.c.
3829
3830 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3831 mount the root filesystem
3832
3833 rootflags= [KNL] Set root filesystem mount option string
3834
3835 rootfstype= [KNL] Set root filesystem type
3836
3837 rootwait [KNL] Wait (indefinitely) for root device to show up.
3838 Useful for devices that are detected asynchronously
3839 (e.g. USB and MMC devices).
3840
3841 rproc_mem=nn[KMG][@address]
3842 [KNL,ARM,CMA] Remoteproc physical memory block.
3843 Memory area to be used by remote processor image,
3844 managed by CMA.
3845
3846 rw [KNL] Mount root device read-write on boot
3847
3848 S [KNL] Run init in single mode
3849
3850 s390_iommu= [HW,S390]
3851 Set s390 IOTLB flushing mode
3852 strict
3853 With strict flushing every unmap operation will result in
3854 an IOTLB flush. Default is lazy flushing before reuse,
3855 which is faster.
3856
3857 sa1100ir [NET]
3858 See drivers/net/irda/sa1100_ir.c.
3859
3860 sbni= [NET] Granch SBNI12 leased line adapter
3861
3862 sched_debug [KNL] Enables verbose scheduler debug messages.
3863
3864 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3865 Allowed values are enable and disable. This feature
3866 incurs a small amount of overhead in the scheduler
3867 but is useful for debugging and performance tuning.
3868
3869 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3870 xtime_lock contention on larger systems, and/or RCU lock
3871 contention on all systems with CONFIG_MAXSMP set.
3872 Format: { "0" | "1" }
3873 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3874 1 -- enable.
3875 Note: increases power consumption, thus should only be
3876 enabled if running jitter sensitive (HPC/RT) workloads.
3877
3878 security= [SECURITY] Choose a security module to enable at boot.
3879 If this boot parameter is not specified, only the first
3880 security module asking for security registration will be
3881 loaded. An invalid security module name will be treated
3882 as if no module has been chosen.
3883
3884 selinux= [SELINUX] Disable or enable SELinux at boot time.
3885 Format: { "0" | "1" }
3886 See security/selinux/Kconfig help text.
3887 0 -- disable.
3888 1 -- enable.
3889 Default value is set via kernel config option.
3890 If enabled at boot time, /selinux/disable can be used
3891 later to disable prior to initial policy load.
3892
3893 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3894 Format: { "0" | "1" }
3895 See security/apparmor/Kconfig help text
3896 0 -- disable.
3897 1 -- enable.
3898 Default value is set via kernel config option.
3899
3900 serialnumber [BUGS=X86-32]
3901
3902 shapers= [NET]
3903 Maximal number of shapers.
3904
3905 simeth= [IA-64]
3906 simscsi=
3907
3908 slram= [HW,MTD]
3909
3910 slab_nomerge [MM]
3911 Disable merging of slabs with similar size. May be
3912 necessary if there is some reason to distinguish
3913 allocs to different slabs, especially in hardened
3914 environments where the risk of heap overflows and
3915 layout control by attackers can usually be
3916 frustrated by disabling merging. This will reduce
3917 most of the exposure of a heap attack to a single
3918 cache (risks via metadata attacks are mostly
3919 unchanged). Debug options disable merging on their
3920 own.
3921 For more information see Documentation/vm/slub.txt.
3922
3923 slab_max_order= [MM, SLAB]
3924 Determines the maximum allowed order for slabs.
3925 A high setting may cause OOMs due to memory
3926 fragmentation. Defaults to 1 for systems with
3927 more than 32MB of RAM, 0 otherwise.
3928
3929 slub_debug[=options[,slabs]] [MM, SLUB]
3930 Enabling slub_debug allows one to determine the
3931 culprit if slab objects become corrupted. Enabling
3932 slub_debug can create guard zones around objects and
3933 may poison objects when not in use. Also tracks the
3934 last alloc / free. For more information see
3935 Documentation/vm/slub.txt.
3936
3937 slub_memcg_sysfs= [MM, SLUB]
3938 Determines whether to enable sysfs directories for
3939 memory cgroup sub-caches. 1 to enable, 0 to disable.
3940 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
3941 Enabling this can lead to a very high number of debug
3942 directories and files being created under
3943 /sys/kernel/slub.
3944
3945 slub_max_order= [MM, SLUB]
3946 Determines the maximum allowed order for slabs.
3947 A high setting may cause OOMs due to memory
3948 fragmentation. For more information see
3949 Documentation/vm/slub.txt.
3950
3951 slub_min_objects= [MM, SLUB]
3952 The minimum number of objects per slab. SLUB will
3953 increase the slab order up to slub_max_order to
3954 generate a sufficiently large slab able to contain
3955 the number of objects indicated. The higher the number
3956 of objects the smaller the overhead of tracking slabs
3957 and the less frequently locks need to be acquired.
3958 For more information see Documentation/vm/slub.txt.
3959
3960 slub_min_order= [MM, SLUB]
3961 Determines the minimum page order for slabs. Must be
3962 lower than slub_max_order.
3963 For more information see Documentation/vm/slub.txt.
3964
3965 slub_nomerge [MM, SLUB]
3966 Same with slab_nomerge. This is supported for legacy.
3967 See slab_nomerge for more information.
3968
3969 smart2= [HW]
3970 Format: <io1>[,<io2>[,...,<io8>]]
3971
3972 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3973 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3974 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3975 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3976 smsc-ircc2.ircc_irq= [HW] IRQ line
3977 smsc-ircc2.ircc_dma= [HW] DMA channel
3978 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3979 0: Toshiba Satellite 1800 (GP data pin select)
3980 1: Fast pin select (default)
3981 2: ATC IRMode
3982
3983 smt [KNL,S390] Set the maximum number of threads (logical
3984 CPUs) to use per physical CPU on systems capable of
3985 symmetric multithreading (SMT). Will be capped to the
3986 actual hardware limit.
3987 Format: <integer>
3988 Default: -1 (no limit)
3989
3990 softlockup_panic=
3991 [KNL] Should the soft-lockup detector generate panics.
3992 Format: <integer>
3993
3994 A nonzero value instructs the soft-lockup detector
3995 to panic the machine when a soft-lockup occurs. This
3996 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
3997 which is the respective build-time switch to that
3998 functionality.
3999
4000 softlockup_all_cpu_backtrace=
4001 [KNL] Should the soft-lockup detector generate
4002 backtraces on all cpus.
4003 Format: <integer>
4004
4005 sonypi.*= [HW] Sony Programmable I/O Control Device driver
4006 See Documentation/laptops/sonypi.txt
4007
4008 spectre_v2= [X86] Control mitigation of Spectre variant 2
4009 (indirect branch speculation) vulnerability.
4010
4011 on - unconditionally enable
4012 off - unconditionally disable
4013 auto - kernel detects whether your CPU model is
4014 vulnerable
4015
4016 Selecting 'on' will, and 'auto' may, choose a
4017 mitigation method at run time according to the
4018 CPU, the available microcode, the setting of the
4019 CONFIG_RETPOLINE configuration option, and the
4020 compiler with which the kernel was built.
4021
4022 Specific mitigations can also be selected manually:
4023
4024 retpoline - replace indirect branches
4025 retpoline,generic - google's original retpoline
4026 retpoline,amd - AMD-specific minimal thunk
4027
4028 Not specifying this option is equivalent to
4029 spectre_v2=auto.
4030
4031 spec_store_bypass_disable=
4032 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
4033 (Speculative Store Bypass vulnerability)
4034
4035 Certain CPUs are vulnerable to an exploit against a
4036 a common industry wide performance optimization known
4037 as "Speculative Store Bypass" in which recent stores
4038 to the same memory location may not be observed by
4039 later loads during speculative execution. The idea
4040 is that such stores are unlikely and that they can
4041 be detected prior to instruction retirement at the
4042 end of a particular speculation execution window.
4043
4044 In vulnerable processors, the speculatively forwarded
4045 store can be used in a cache side channel attack, for
4046 example to read memory to which the attacker does not
4047 directly have access (e.g. inside sandboxed code).
4048
4049 This parameter controls whether the Speculative Store
4050 Bypass optimization is used.
4051
4052 on - Unconditionally disable Speculative Store Bypass
4053 off - Unconditionally enable Speculative Store Bypass
4054 auto - Kernel detects whether the CPU model contains an
4055 implementation of Speculative Store Bypass and
4056 picks the most appropriate mitigation. If the
4057 CPU is not vulnerable, "off" is selected. If the
4058 CPU is vulnerable the default mitigation is
4059 architecture and Kconfig dependent. See below.
4060 prctl - Control Speculative Store Bypass per thread
4061 via prctl. Speculative Store Bypass is enabled
4062 for a process by default. The state of the control
4063 is inherited on fork.
4064 seccomp - Same as "prctl" above, but all seccomp threads
4065 will disable SSB unless they explicitly opt out.
4066
4067 Not specifying this option is equivalent to
4068 spec_store_bypass_disable=auto.
4069
4070 Default mitigations:
4071 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
4072
4073 spia_io_base= [HW,MTD]
4074 spia_fio_base=
4075 spia_pedr=
4076 spia_peddr=
4077
4078 srcutree.counter_wrap_check [KNL]
4079 Specifies how frequently to check for
4080 grace-period sequence counter wrap for the
4081 srcu_data structure's ->srcu_gp_seq_needed field.
4082 The greater the number of bits set in this kernel
4083 parameter, the less frequently counter wrap will
4084 be checked for. Note that the bottom two bits
4085 are ignored.
4086
4087 srcutree.exp_holdoff [KNL]
4088 Specifies how many nanoseconds must elapse
4089 since the end of the last SRCU grace period for
4090 a given srcu_struct until the next normal SRCU
4091 grace period will be considered for automatic
4092 expediting. Set to zero to disable automatic
4093 expediting.
4094
4095 stack_guard_gap= [MM]
4096 override the default stack gap protection. The value
4097 is in page units and it defines how many pages prior
4098 to (for stacks growing down) resp. after (for stacks
4099 growing up) the main stack are reserved for no other
4100 mapping. Default value is 256 pages.
4101
4102 stacktrace [FTRACE]
4103 Enabled the stack tracer on boot up.
4104
4105 stacktrace_filter=[function-list]
4106 [FTRACE] Limit the functions that the stack tracer
4107 will trace at boot up. function-list is a comma separated
4108 list of functions. This list can be changed at run
4109 time by the stack_trace_filter file in the debugfs
4110 tracing directory. Note, this enables stack tracing
4111 and the stacktrace above is not needed.
4112
4113 sti= [PARISC,HW]
4114 Format: <num>
4115 Set the STI (builtin display/keyboard on the HP-PARISC
4116 machines) console (graphic card) which should be used
4117 as the initial boot-console.
4118 See also comment in drivers/video/console/sticore.c.
4119
4120 sti_font= [HW]
4121 See comment in drivers/video/console/sticore.c.
4122
4123 stifb= [HW]
4124 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
4125
4126 sunrpc.min_resvport=
4127 sunrpc.max_resvport=
4128 [NFS,SUNRPC]
4129 SunRPC servers often require that client requests
4130 originate from a privileged port (i.e. a port in the
4131 range 0 < portnr < 1024).
4132 An administrator who wishes to reserve some of these
4133 ports for other uses may adjust the range that the
4134 kernel's sunrpc client considers to be privileged
4135 using these two parameters to set the minimum and
4136 maximum port values.
4137
4138 sunrpc.svc_rpc_per_connection_limit=
4139 [NFS,SUNRPC]
4140 Limit the number of requests that the server will
4141 process in parallel from a single connection.
4142 The default value is 0 (no limit).
4143
4144 sunrpc.pool_mode=
4145 [NFS]
4146 Control how the NFS server code allocates CPUs to
4147 service thread pools. Depending on how many NICs
4148 you have and where their interrupts are bound, this
4149 option will affect which CPUs will do NFS serving.
4150 Note: this parameter cannot be changed while the
4151 NFS server is running.
4152
4153 auto the server chooses an appropriate mode
4154 automatically using heuristics
4155 global a single global pool contains all CPUs
4156 percpu one pool for each CPU
4157 pernode one pool for each NUMA node (equivalent
4158 to global on non-NUMA machines)
4159
4160 sunrpc.tcp_slot_table_entries=
4161 sunrpc.udp_slot_table_entries=
4162 [NFS,SUNRPC]
4163 Sets the upper limit on the number of simultaneous
4164 RPC calls that can be sent from the client to a
4165 server. Increasing these values may allow you to
4166 improve throughput, but will also increase the
4167 amount of memory reserved for use by the client.
4168
4169 suspend.pm_test_delay=
4170 [SUSPEND]
4171 Sets the number of seconds to remain in a suspend test
4172 mode before resuming the system (see
4173 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4174 is set. Default value is 5.
4175
4176 swapaccount=[0|1]
4177 [KNL] Enable accounting of swap in memory resource
4178 controller if no parameter or 1 is given or disable
4179 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4180
4181 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
4182 Format: { <int> | force | noforce }
4183 <int> -- Number of I/O TLB slabs
4184 force -- force using of bounce buffers even if they
4185 wouldn't be automatically used by the kernel
4186 noforce -- Never use bounce buffers (for debugging)
4187
4188 switches= [HW,M68k]
4189
4190 sysfs.deprecated=0|1 [KNL]
4191 Enable/disable old style sysfs layout for old udev
4192 on older distributions. When this option is enabled
4193 very new udev will not work anymore. When this option
4194 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4195 in older udev will not work anymore.
4196 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4197 the kernel configuration.
4198
4199 sysrq_always_enabled
4200 [KNL]
4201 Ignore sysrq setting - this boot parameter will
4202 neutralize any effect of /proc/sys/kernel/sysrq.
4203 Useful for debugging.
4204
4205 tcpmhash_entries= [KNL,NET]
4206 Set the number of tcp_metrics_hash slots.
4207 Default value is 8192 or 16384 depending on total
4208 ram pages. This is used to specify the TCP metrics
4209 cache size. See Documentation/networking/ip-sysctl.txt
4210 "tcp_no_metrics_save" section for more details.
4211
4212 tdfx= [HW,DRM]
4213
4214 test_suspend= [SUSPEND][,N]
4215 Specify "mem" (for Suspend-to-RAM) or "standby" (for
4216 standby suspend) or "freeze" (for suspend type freeze)
4217 as the system sleep state during system startup with
4218 the optional capability to repeat N number of times.
4219 The system is woken from this state using a
4220 wakeup-capable RTC alarm.
4221
4222 thash_entries= [KNL,NET]
4223 Set number of hash buckets for TCP connection
4224
4225 thermal.act= [HW,ACPI]
4226 -1: disable all active trip points in all thermal zones
4227 <degrees C>: override all lowest active trip points
4228
4229 thermal.crt= [HW,ACPI]
4230 -1: disable all critical trip points in all thermal zones
4231 <degrees C>: override all critical trip points
4232
4233 thermal.nocrt= [HW,ACPI]
4234 Set to disable actions on ACPI thermal zone
4235 critical and hot trip points.
4236
4237 thermal.off= [HW,ACPI]
4238 1: disable ACPI thermal control
4239
4240 thermal.psv= [HW,ACPI]
4241 -1: disable all passive trip points
4242 <degrees C>: override all passive trip points to this
4243 value
4244
4245 thermal.tzp= [HW,ACPI]
4246 Specify global default ACPI thermal zone polling rate
4247 <deci-seconds>: poll all this frequency
4248 0: no polling (default)
4249
4250 threadirqs [KNL]
4251 Force threading of all interrupt handlers except those
4252 marked explicitly IRQF_NO_THREAD.
4253
4254 tmem [KNL,XEN]
4255 Enable the Transcendent memory driver if built-in.
4256
4257 tmem.cleancache=0|1 [KNL, XEN]
4258 Default is on (1). Disable the usage of the cleancache
4259 API to send anonymous pages to the hypervisor.
4260
4261 tmem.frontswap=0|1 [KNL, XEN]
4262 Default is on (1). Disable the usage of the frontswap
4263 API to send swap pages to the hypervisor. If disabled
4264 the selfballooning and selfshrinking are force disabled.
4265
4266 tmem.selfballooning=0|1 [KNL, XEN]
4267 Default is on (1). Disable the driving of swap pages
4268 to the hypervisor.
4269
4270 tmem.selfshrinking=0|1 [KNL, XEN]
4271 Default is on (1). Partial swapoff that immediately
4272 transfers pages from Xen hypervisor back to the
4273 kernel based on different criteria.
4274
4275 topology= [S390]
4276 Format: {off | on}
4277 Specify if the kernel should make use of the cpu
4278 topology information if the hardware supports this.
4279 The scheduler will make use of this information and
4280 e.g. base its process migration decisions on it.
4281 Default is on.
4282
4283 topology_updates= [KNL, PPC, NUMA]
4284 Format: {off}
4285 Specify if the kernel should ignore (off)
4286 topology updates sent by the hypervisor to this
4287 LPAR.
4288
4289 tp720= [HW,PS2]
4290
4291 tpm_suspend_pcr=[HW,TPM]
4292 Format: integer pcr id
4293 Specify that at suspend time, the tpm driver
4294 should extend the specified pcr with zeros,
4295 as a workaround for some chips which fail to
4296 flush the last written pcr on TPM_SaveState.
4297 This will guarantee that all the other pcrs
4298 are saved.
4299
4300 trace_buf_size=nn[KMG]
4301 [FTRACE] will set tracing buffer size on each cpu.
4302
4303 trace_event=[event-list]
4304 [FTRACE] Set and start specified trace events in order
4305 to facilitate early boot debugging. The event-list is a
4306 comma separated list of trace events to enable. See
4307 also Documentation/trace/events.txt
4308
4309 trace_options=[option-list]
4310 [FTRACE] Enable or disable tracer options at boot.
4311 The option-list is a comma delimited list of options
4312 that can be enabled or disabled just as if you were
4313 to echo the option name into
4314
4315 /sys/kernel/debug/tracing/trace_options
4316
4317 For example, to enable stacktrace option (to dump the
4318 stack trace of each event), add to the command line:
4319
4320 trace_options=stacktrace
4321
4322 See also Documentation/trace/ftrace.txt "trace options"
4323 section.
4324
4325 tp_printk[FTRACE]
4326 Have the tracepoints sent to printk as well as the
4327 tracing ring buffer. This is useful for early boot up
4328 where the system hangs or reboots and does not give the
4329 option for reading the tracing buffer or performing a
4330 ftrace_dump_on_oops.
4331
4332 To turn off having tracepoints sent to printk,
4333 echo 0 > /proc/sys/kernel/tracepoint_printk
4334 Note, echoing 1 into this file without the
4335 tracepoint_printk kernel cmdline option has no effect.
4336
4337 ** CAUTION **
4338
4339 Having tracepoints sent to printk() and activating high
4340 frequency tracepoints such as irq or sched, can cause
4341 the system to live lock.
4342
4343 traceoff_on_warning
4344 [FTRACE] enable this option to disable tracing when a
4345 warning is hit. This turns off "tracing_on". Tracing can
4346 be enabled again by echoing '1' into the "tracing_on"
4347 file located in /sys/kernel/debug/tracing/
4348
4349 This option is useful, as it disables the trace before
4350 the WARNING dump is called, which prevents the trace to
4351 be filled with content caused by the warning output.
4352
4353 This option can also be set at run time via the sysctl
4354 option: kernel/traceoff_on_warning
4355
4356 transparent_hugepage=
4357 [KNL]
4358 Format: [always|madvise|never]
4359 Can be used to control the default behavior of the system
4360 with respect to transparent hugepages.
4361 See Documentation/vm/transhuge.txt for more details.
4362
4363 tsc= Disable clocksource stability checks for TSC.
4364 Format: <string>
4365 [x86] reliable: mark tsc clocksource as reliable, this
4366 disables clocksource verification at runtime, as well
4367 as the stability checks done at bootup. Used to enable
4368 high-resolution timer mode on older hardware, and in
4369 virtualized environment.
4370 [x86] noirqtime: Do not use TSC to do irq accounting.
4371 Used to run time disable IRQ_TIME_ACCOUNTING on any
4372 platforms where RDTSC is slow and this accounting
4373 can add overhead.
4374 [x86] unstable: mark the TSC clocksource as unstable, this
4375 marks the TSC unconditionally unstable at bootup and
4376 avoids any further wobbles once the TSC watchdog notices.
4377
4378 turbografx.map[2|3]= [HW,JOY]
4379 TurboGraFX parallel port interface
4380 Format:
4381 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4382 See also Documentation/input/devices/joystick-parport.rst
4383
4384 udbg-immortal [PPC] When debugging early kernel crashes that
4385 happen after console_init() and before a proper
4386 console driver takes over, this boot options might
4387 help "seeing" what's going on.
4388
4389 uhash_entries= [KNL,NET]
4390 Set number of hash buckets for UDP/UDP-Lite connections
4391
4392 uhci-hcd.ignore_oc=
4393 [USB] Ignore overcurrent events (default N).
4394 Some badly-designed motherboards generate lots of
4395 bogus events, for ports that aren't wired to
4396 anything. Set this parameter to avoid log spamming.
4397 Note that genuine overcurrent events won't be
4398 reported either.
4399
4400 unknown_nmi_panic
4401 [X86] Cause panic on unknown NMI.
4402
4403 usbcore.authorized_default=
4404 [USB] Default USB device authorization:
4405 (default -1 = authorized except for wireless USB,
4406 0 = not authorized, 1 = authorized)
4407
4408 usbcore.autosuspend=
4409 [USB] The autosuspend time delay (in seconds) used
4410 for newly-detected USB devices (default 2). This
4411 is the time required before an idle device will be
4412 autosuspended. Devices for which the delay is set
4413 to a negative value won't be autosuspended at all.
4414
4415 usbcore.usbfs_snoop=
4416 [USB] Set to log all usbfs traffic (default 0 = off).
4417
4418 usbcore.usbfs_snoop_max=
4419 [USB] Maximum number of bytes to snoop in each URB
4420 (default = 65536).
4421
4422 usbcore.blinkenlights=
4423 [USB] Set to cycle leds on hubs (default 0 = off).
4424
4425 usbcore.old_scheme_first=
4426 [USB] Start with the old device initialization
4427 scheme (default 0 = off).
4428
4429 usbcore.usbfs_memory_mb=
4430 [USB] Memory limit (in MB) for buffers allocated by
4431 usbfs (default = 16, 0 = max = 2047).
4432
4433 usbcore.use_both_schemes=
4434 [USB] Try the other device initialization scheme
4435 if the first one fails (default 1 = enabled).
4436
4437 usbcore.initial_descriptor_timeout=
4438 [USB] Specifies timeout for the initial 64-byte
4439 USB_REQ_GET_DESCRIPTOR request in milliseconds
4440 (default 5000 = 5.0 seconds).
4441
4442 usbcore.nousb [USB] Disable the USB subsystem
4443
4444 usbcore.quirks=
4445 [USB] A list of quirk entries to augment the built-in
4446 usb core quirk list. List entries are separated by
4447 commas. Each entry has the form
4448 VendorID:ProductID:Flags. The IDs are 4-digit hex
4449 numbers and Flags is a set of letters. Each letter
4450 will change the built-in quirk; setting it if it is
4451 clear and clearing it if it is set. The letters have
4452 the following meanings:
4453 a = USB_QUIRK_STRING_FETCH_255 (string
4454 descriptors must not be fetched using
4455 a 255-byte read);
4456 b = USB_QUIRK_RESET_RESUME (device can't resume
4457 correctly so reset it instead);
4458 c = USB_QUIRK_NO_SET_INTF (device can't handle
4459 Set-Interface requests);
4460 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
4461 handle its Configuration or Interface
4462 strings);
4463 e = USB_QUIRK_RESET (device can't be reset
4464 (e.g morph devices), don't use reset);
4465 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
4466 more interface descriptions than the
4467 bNumInterfaces count, and can't handle
4468 talking to these interfaces);
4469 g = USB_QUIRK_DELAY_INIT (device needs a pause
4470 during initialization, after we read
4471 the device descriptor);
4472 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
4473 high speed and super speed interrupt
4474 endpoints, the USB 2.0 and USB 3.0 spec
4475 require the interval in microframes (1
4476 microframe = 125 microseconds) to be
4477 calculated as interval = 2 ^
4478 (bInterval-1).
4479 Devices with this quirk report their
4480 bInterval as the result of this
4481 calculation instead of the exponent
4482 variable used in the calculation);
4483 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
4484 handle device_qualifier descriptor
4485 requests);
4486 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
4487 generates spurious wakeup, ignore
4488 remote wakeup capability);
4489 k = USB_QUIRK_NO_LPM (device can't handle Link
4490 Power Management);
4491 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
4492 (Device reports its bInterval as linear
4493 frames instead of the USB 2.0
4494 calculation);
4495 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
4496 to be disconnected before suspend to
4497 prevent spurious wakeup);
4498 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
4499 pause after every control message);
4500 Example: quirks=0781:5580:bk,0a5c:5834:gij
4501
4502 usbhid.mousepoll=
4503 [USBHID] The interval which mice are to be polled at.
4504
4505 usbhid.jspoll=
4506 [USBHID] The interval which joysticks are to be polled at.
4507
4508 usbhid.kbpoll=
4509 [USBHID] The interval which keyboards are to be polled at.
4510
4511 usb-storage.delay_use=
4512 [UMS] The delay in seconds before a new device is
4513 scanned for Logical Units (default 1).
4514
4515 usb-storage.quirks=
4516 [UMS] A list of quirks entries to supplement or
4517 override the built-in unusual_devs list. List
4518 entries are separated by commas. Each entry has
4519 the form VID:PID:Flags where VID and PID are Vendor
4520 and Product ID values (4-digit hex numbers) and
4521 Flags is a set of characters, each corresponding
4522 to a common usb-storage quirk flag as follows:
4523 a = SANE_SENSE (collect more than 18 bytes
4524 of sense data);
4525 b = BAD_SENSE (don't collect more than 18
4526 bytes of sense data);
4527 c = FIX_CAPACITY (decrease the reported
4528 device capacity by one sector);
4529 d = NO_READ_DISC_INFO (don't use
4530 READ_DISC_INFO command);
4531 e = NO_READ_CAPACITY_16 (don't use
4532 READ_CAPACITY_16 command);
4533 f = NO_REPORT_OPCODES (don't use report opcodes
4534 command, uas only);
4535 g = MAX_SECTORS_240 (don't transfer more than
4536 240 sectors at a time, uas only);
4537 h = CAPACITY_HEURISTICS (decrease the
4538 reported device capacity by one
4539 sector if the number is odd);
4540 i = IGNORE_DEVICE (don't bind to this
4541 device);
4542 j = NO_REPORT_LUNS (don't use report luns
4543 command, uas only);
4544 l = NOT_LOCKABLE (don't try to lock and
4545 unlock ejectable media);
4546 m = MAX_SECTORS_64 (don't transfer more
4547 than 64 sectors = 32 KB at a time);
4548 n = INITIAL_READ10 (force a retry of the
4549 initial READ(10) command);
4550 o = CAPACITY_OK (accept the capacity
4551 reported by the device);
4552 p = WRITE_CACHE (the device cache is ON
4553 by default);
4554 r = IGNORE_RESIDUE (the device reports
4555 bogus residue values);
4556 s = SINGLE_LUN (the device has only one
4557 Logical Unit);
4558 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4559 commands, uas only);
4560 u = IGNORE_UAS (don't bind to the uas driver);
4561 w = NO_WP_DETECT (don't test whether the
4562 medium is write-protected).
4563 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4564 even if the device claims no cache)
4565 Example: quirks=0419:aaf5:rl,0421:0433:rc
4566
4567 user_debug= [KNL,ARM]
4568 Format: <int>
4569 See arch/arm/Kconfig.debug help text.
4570 1 - undefined instruction events
4571 2 - system calls
4572 4 - invalid data aborts
4573 8 - SIGSEGV faults
4574 16 - SIGBUS faults
4575 Example: user_debug=31
4576
4577 userpte=
4578 [X86] Flags controlling user PTE allocations.
4579
4580 nohigh = do not allocate PTE pages in
4581 HIGHMEM regardless of setting
4582 of CONFIG_HIGHPTE.
4583
4584 vdso= [X86,SH]
4585 On X86_32, this is an alias for vdso32=. Otherwise:
4586
4587 vdso=1: enable VDSO (the default)
4588 vdso=0: disable VDSO mapping
4589
4590 vdso32= [X86] Control the 32-bit vDSO
4591 vdso32=1: enable 32-bit VDSO
4592 vdso32=0 or vdso32=2: disable 32-bit VDSO
4593
4594 See the help text for CONFIG_COMPAT_VDSO for more
4595 details. If CONFIG_COMPAT_VDSO is set, the default is
4596 vdso32=0; otherwise, the default is vdso32=1.
4597
4598 For compatibility with older kernels, vdso32=2 is an
4599 alias for vdso32=0.
4600
4601 Try vdso32=0 if you encounter an error that says:
4602 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4603
4604 vector= [IA-64,SMP]
4605 vector=percpu: enable percpu vector domain
4606
4607 video= [FB] Frame buffer configuration
4608 See Documentation/fb/modedb.txt.
4609
4610 video.brightness_switch_enabled= [0,1]
4611 If set to 1, on receiving an ACPI notify event
4612 generated by hotkey, video driver will adjust brightness
4613 level and then send out the event to user space through
4614 the allocated input device; If set to 0, video driver
4615 will only send out the event without touching backlight
4616 brightness level.
4617 default: 1
4618
4619 virtio_mmio.device=
4620 [VMMIO] Memory mapped virtio (platform) device.
4621
4622 <size>@<baseaddr>:<irq>[:<id>]
4623 where:
4624 <size> := size (can use standard suffixes
4625 like K, M and G)
4626 <baseaddr> := physical base address
4627 <irq> := interrupt number (as passed to
4628 request_irq())
4629 <id> := (optional) platform device id
4630 example:
4631 virtio_mmio.device=1K@0x100b0000:48:7
4632
4633 Can be used multiple times for multiple devices.
4634
4635 vga= [BOOT,X86-32] Select a particular video mode
4636 See Documentation/x86/boot.txt and
4637 Documentation/svga.txt.
4638 Use vga=ask for menu.
4639 This is actually a boot loader parameter; the value is
4640 passed to the kernel using a special protocol.
4641
4642 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4643 size of <nn>. This can be used to increase the
4644 minimum size (128MB on x86). It can also be used to
4645 decrease the size and leave more room for directly
4646 mapped kernel RAM.
4647
4648 vmcp_cma=nn[MG] [KNL,S390]
4649 Sets the memory size reserved for contiguous memory
4650 allocations for the vmcp device driver.
4651
4652 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4653 Format: <command>
4654
4655 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4656 Format: <command>
4657
4658 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4659 Format: <command>
4660
4661 vsyscall= [X86-64]
4662 Controls the behavior of vsyscalls (i.e. calls to
4663 fixed addresses of 0xffffffffff600x00 from legacy
4664 code). Most statically-linked binaries and older
4665 versions of glibc use these calls. Because these
4666 functions are at fixed addresses, they make nice
4667 targets for exploits that can control RIP.
4668
4669 emulate [default] Vsyscalls turn into traps and are
4670 emulated reasonably safely.
4671
4672 native Vsyscalls are native syscall instructions.
4673 This is a little bit faster than trapping
4674 and makes a few dynamic recompilers work
4675 better than they would in emulation mode.
4676 It also makes exploits much easier to write.
4677
4678 none Vsyscalls don't work at all. This makes
4679 them quite hard to use for exploits but
4680 might break your system.
4681
4682 vt.color= [VT] Default text color.
4683 Format: 0xYX, X = foreground, Y = background.
4684 Default: 0x07 = light gray on black.
4685
4686 vt.cur_default= [VT] Default cursor shape.
4687 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4688 the parameters of the <Esc>[?A;B;Cc escape sequence;
4689 see VGA-softcursor.txt. Default: 2 = underline.
4690
4691 vt.default_blu= [VT]
4692 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4693 Change the default blue palette of the console.
4694 This is a 16-member array composed of values
4695 ranging from 0-255.
4696
4697 vt.default_grn= [VT]
4698 Format: <green0>,<green1>,<green2>,...,<green15>
4699 Change the default green palette of the console.
4700 This is a 16-member array composed of values
4701 ranging from 0-255.
4702
4703 vt.default_red= [VT]
4704 Format: <red0>,<red1>,<red2>,...,<red15>
4705 Change the default red palette of the console.
4706 This is a 16-member array composed of values
4707 ranging from 0-255.
4708
4709 vt.default_utf8=
4710 [VT]
4711 Format=<0|1>
4712 Set system-wide default UTF-8 mode for all tty's.
4713 Default is 1, i.e. UTF-8 mode is enabled for all
4714 newly opened terminals.
4715
4716 vt.global_cursor_default=
4717 [VT]
4718 Format=<-1|0|1>
4719 Set system-wide default for whether a cursor
4720 is shown on new VTs. Default is -1,
4721 i.e. cursors will be created by default unless
4722 overridden by individual drivers. 0 will hide
4723 cursors, 1 will display them.
4724
4725 vt.italic= [VT] Default color for italic text; 0-15.
4726 Default: 2 = green.
4727
4728 vt.underline= [VT] Default color for underlined text; 0-15.
4729 Default: 3 = cyan.
4730
4731 watchdog timers [HW,WDT] For information on watchdog timers,
4732 see Documentation/watchdog/watchdog-parameters.txt
4733 or other driver-specific files in the
4734 Documentation/watchdog/ directory.
4735
4736 workqueue.watchdog_thresh=
4737 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4738 warn stall conditions and dump internal state to
4739 help debugging. 0 disables workqueue stall
4740 detection; otherwise, it's the stall threshold
4741 duration in seconds. The default value is 30 and
4742 it can be updated at runtime by writing to the
4743 corresponding sysfs file.
4744
4745 workqueue.disable_numa
4746 By default, all work items queued to unbound
4747 workqueues are affine to the NUMA nodes they're
4748 issued on, which results in better behavior in
4749 general. If NUMA affinity needs to be disabled for
4750 whatever reason, this option can be used. Note
4751 that this also can be controlled per-workqueue for
4752 workqueues visible under /sys/bus/workqueue/.
4753
4754 workqueue.power_efficient
4755 Per-cpu workqueues are generally preferred because
4756 they show better performance thanks to cache
4757 locality; unfortunately, per-cpu workqueues tend to
4758 be more power hungry than unbound workqueues.
4759
4760 Enabling this makes the per-cpu workqueues which
4761 were observed to contribute significantly to power
4762 consumption unbound, leading to measurably lower
4763 power usage at the cost of small performance
4764 overhead.
4765
4766 The default value of this parameter is determined by
4767 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4768
4769 workqueue.debug_force_rr_cpu
4770 Workqueue used to implicitly guarantee that work
4771 items queued without explicit CPU specified are put
4772 on the local CPU. This guarantee is no longer true
4773 and while local CPU is still preferred work items
4774 may be put on foreign CPUs. This debug option
4775 forces round-robin CPU selection to flush out
4776 usages which depend on the now broken guarantee.
4777 When enabled, memory and cache locality will be
4778 impacted.
4779
4780 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4781 default x2apic cluster mode on platforms
4782 supporting x2apic.
4783
4784 x86_intel_mid_timer= [X86-32,APBT]
4785 Choose timer option for x86 Intel MID platform.
4786 Two valid options are apbt timer only and lapic timer
4787 plus one apbt timer for broadcast timer.
4788 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4789
4790 xen_512gb_limit [KNL,X86-64,XEN]
4791 Restricts the kernel running paravirtualized under Xen
4792 to use only up to 512 GB of RAM. The reason to do so is
4793 crash analysis tools and Xen tools for doing domain
4794 save/restore/migration must be enabled to handle larger
4795 domains.
4796
4797 xen_emul_unplug= [HW,X86,XEN]
4798 Unplug Xen emulated devices
4799 Format: [unplug0,][unplug1]
4800 ide-disks -- unplug primary master IDE devices
4801 aux-ide-disks -- unplug non-primary-master IDE devices
4802 nics -- unplug network devices
4803 all -- unplug all emulated devices (NICs and IDE disks)
4804 unnecessary -- unplugging emulated devices is
4805 unnecessary even if the host did not respond to
4806 the unplug protocol
4807 never -- do not unplug even if version check succeeds
4808
4809 xen_nopvspin [X86,XEN]
4810 Disables the ticketlock slowpath using Xen PV
4811 optimizations.
4812
4813 xen_nopv [X86]
4814 Disables the PV optimizations forcing the HVM guest to
4815 run as generic HVM guest with no PV drivers.
4816
4817 xirc2ps_cs= [NET,PCMCIA]
4818 Format:
4819 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1 acpi= [HW,ACPI,X86,ARM64]
2 Advanced Configuration and Power Interface
3 Format: { force | on | off | strict | noirq | rsdt |
4 copy_dsdt }
5 force -- enable ACPI if default was off
6 on -- enable ACPI but allow fallback to DT [arm64]
7 off -- disable ACPI if default was on
8 noirq -- do not use ACPI for IRQ routing
9 strict -- Be less tolerant of platforms that are not
10 strictly ACPI specification compliant.
11 rsdt -- prefer RSDT over (default) XSDT
12 copy_dsdt -- copy DSDT to memory
13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
14 are available
15
16 See also Documentation/power/runtime_pm.txt, pci=noacpi
17
18 acpi_apic_instance= [ACPI, IOAPIC]
19 Format: <int>
20 2: use 2nd APIC table, if available
21 1,0: use 1st APIC table
22 default: 0
23
24 acpi_backlight= [HW,ACPI]
25 acpi_backlight=vendor
26 acpi_backlight=video
27 If set to vendor, prefer vendor specific driver
28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
29 of the ACPI video.ko driver.
30
31 acpi_force_32bit_fadt_addr
32 force FADT to use 32 bit addresses rather than the
33 64 bit X_* addresses. Some firmware have broken 64
34 bit addresses for force ACPI ignore these and use
35 the older legacy 32 bit addresses.
36
37 acpica_no_return_repair [HW, ACPI]
38 Disable AML predefined validation mechanism
39 This mechanism can repair the evaluation result to make
40 the return objects more ACPI specification compliant.
41 This option is useful for developers to identify the
42 root cause of an AML interpreter issue when the issue
43 has something to do with the repair mechanism.
44
45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
47 Format: <int>
48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49 debug output. Bits in debug_layer correspond to a
50 _COMPONENT in an ACPI source file, e.g.,
51 #define _COMPONENT ACPI_PCI_COMPONENT
52 Bits in debug_level correspond to a level in
53 ACPI_DEBUG_PRINT statements, e.g.,
54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55 The debug_level mask defaults to "info". See
56 Documentation/acpi/debug.txt for more information about
57 debug layers and levels.
58
59 Enable processor driver info messages:
60 acpi.debug_layer=0x20000000
61 Enable PCI/PCI interrupt routing info messages:
62 acpi.debug_layer=0x400000
63 Enable AML "Debug" output, i.e., stores to the Debug
64 object while interpreting AML:
65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66 Enable all messages related to ACPI hardware:
67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
68
69 Some values produce so much output that the system is
70 unusable. The "log_buf_len" parameter may be useful
71 if you need to capture more output.
72
73 acpi_enforce_resources= [ACPI]
74 { strict | lax | no }
75 Check for resource conflicts between native drivers
76 and ACPI OperationRegions (SystemIO and SystemMemory
77 only). IO ports and memory declared in ACPI might be
78 used by the ACPI subsystem in arbitrary AML code and
79 can interfere with legacy drivers.
80 strict (default): access to resources claimed by ACPI
81 is denied; legacy drivers trying to access reserved
82 resources will fail to bind to device using them.
83 lax: access to resources claimed by ACPI is allowed;
84 legacy drivers trying to access reserved resources
85 will bind successfully but a warning message is logged.
86 no: ACPI OperationRegions are not marked as reserved,
87 no further checks are performed.
88
89 acpi_force_table_verification [HW,ACPI]
90 Enable table checksum verification during early stage.
91 By default, this is disabled due to x86 early mapping
92 size limitation.
93
94 acpi_irq_balance [HW,ACPI]
95 ACPI will balance active IRQs
96 default in APIC mode
97
98 acpi_irq_nobalance [HW,ACPI]
99 ACPI will not move active IRQs (default)
100 default in PIC mode
101
102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103 Format: <irq>,<irq>...
104
105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
106 use by PCI
107 Format: <irq>,<irq>...
108
109 acpi_mask_gpe= [HW,ACPI]
110 Due to the existence of _Lxx/_Exx, some GPEs triggered
111 by unsupported hardware/firmware features can result in
112 GPE floodings that cannot be automatically disabled by
113 the GPE dispatcher.
114 This facility can be used to prevent such uncontrolled
115 GPE floodings.
116 Format: <int>
117 Support masking of GPEs numbered from 0x00 to 0x7f.
118
119 acpi_no_auto_serialize [HW,ACPI]
120 Disable auto-serialization of AML methods
121 AML control methods that contain the opcodes to create
122 named objects will be marked as "Serialized" by the
123 auto-serialization feature.
124 This feature is enabled by default.
125 This option allows to turn off the feature.
126
127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
128 kernels.
129
130 acpi_no_static_ssdt [HW,ACPI]
131 Disable installation of static SSDTs at early boot time
132 By default, SSDTs contained in the RSDT/XSDT will be
133 installed automatically and they will appear under
134 /sys/firmware/acpi/tables.
135 This option turns off this feature.
136 Note that specifying this option does not affect
137 dynamic table installation which will install SSDT
138 tables to /sys/firmware/acpi/tables/dynamic.
139
140 acpi_rsdp= [ACPI,EFI,KEXEC]
141 Pass the RSDP address to the kernel, mostly used
142 on machines running EFI runtime service to boot the
143 second kernel for kdump.
144
145 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
146 Format: To spoof as Windows 98: ="Microsoft Windows"
147
148 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
149 of 2 which is mandated by ACPI 6) as the supported ACPI
150 specification revision (when using this switch, it may
151 be necessary to carry out a cold reboot _twice_ in a
152 row to make it take effect on the platform firmware).
153
154 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
155 acpi_osi="string1" # add string1
156 acpi_osi="!string2" # remove string2
157 acpi_osi=!* # remove all strings
158 acpi_osi=! # disable all built-in OS vendor
159 strings
160 acpi_osi=!! # enable all built-in OS vendor
161 strings
162 acpi_osi= # disable all strings
163
164 'acpi_osi=!' can be used in combination with single or
165 multiple 'acpi_osi="string1"' to support specific OS
166 vendor string(s). Note that such command can only
167 affect the default state of the OS vendor strings, thus
168 it cannot affect the default state of the feature group
169 strings and the current state of the OS vendor strings,
170 specifying it multiple times through kernel command line
171 is meaningless. This command is useful when one do not
172 care about the state of the feature group strings which
173 should be controlled by the OSPM.
174 Examples:
175 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
176 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
177 can make '_OSI("Windows 2000")' TRUE.
178
179 'acpi_osi=' cannot be used in combination with other
180 'acpi_osi=' command lines, the _OSI method will not
181 exist in the ACPI namespace. NOTE that such command can
182 only affect the _OSI support state, thus specifying it
183 multiple times through kernel command line is also
184 meaningless.
185 Examples:
186 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
187 FALSE.
188
189 'acpi_osi=!*' can be used in combination with single or
190 multiple 'acpi_osi="string1"' to support specific
191 string(s). Note that such command can affect the
192 current state of both the OS vendor strings and the
193 feature group strings, thus specifying it multiple times
194 through kernel command line is meaningful. But it may
195 still not able to affect the final state of a string if
196 there are quirks related to this string. This command
197 is useful when one want to control the state of the
198 feature group strings to debug BIOS issues related to
199 the OSPM features.
200 Examples:
201 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
202 '_OSI("Module Device")' FALSE.
203 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
204 '_OSI("Module Device")' TRUE.
205 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
206 equivalent to
207 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
208 and
209 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
210 they all will make '_OSI("Windows 2000")' TRUE.
211
212 acpi_pm_good [X86]
213 Override the pmtimer bug detection: force the kernel
214 to assume that this machine's pmtimer latches its value
215 and always returns good values.
216
217 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
218 Format: { level | edge | high | low }
219
220 acpi_skip_timer_override [HW,ACPI]
221 Recognize and ignore IRQ0/pin2 Interrupt Override.
222 For broken nForce2 BIOS resulting in XT-PIC timer.
223
224 acpi_sleep= [HW,ACPI] Sleep options
225 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
226 old_ordering, nonvs, sci_force_enable }
227 See Documentation/power/video.txt for information on
228 s3_bios and s3_mode.
229 s3_beep is for debugging; it makes the PC's speaker beep
230 as soon as the kernel's real-mode entry point is called.
231 s4_nohwsig prevents ACPI hardware signature from being
232 used during resume from hibernation.
233 old_ordering causes the ACPI 1.0 ordering of the _PTS
234 control method, with respect to putting devices into
235 low power states, to be enforced (the ACPI 2.0 ordering
236 of _PTS is used by default).
237 nonvs prevents the kernel from saving/restoring the
238 ACPI NVS memory during suspend/hibernation and resume.
239 sci_force_enable causes the kernel to set SCI_EN directly
240 on resume from S1/S3 (which is against the ACPI spec,
241 but some broken systems don't work without it).
242
243 acpi_use_timer_override [HW,ACPI]
244 Use timer override. For some broken Nvidia NF5 boards
245 that require a timer override, but don't have HPET
246
247 add_efi_memmap [EFI; X86] Include EFI memory map in
248 kernel's map of available physical RAM.
249
250 agp= [AGP]
251 { off | try_unsupported }
252 off: disable AGP support
253 try_unsupported: try to drive unsupported chipsets
254 (may crash computer or cause data corruption)
255
256 ALSA [HW,ALSA]
257 See Documentation/sound/alsa/alsa-parameters.txt
258
259 alignment= [KNL,ARM]
260 Allow the default userspace alignment fault handler
261 behaviour to be specified. Bit 0 enables warnings,
262 bit 1 enables fixups, and bit 2 sends a segfault.
263
264 align_va_addr= [X86-64]
265 Align virtual addresses by clearing slice [14:12] when
266 allocating a VMA at process creation time. This option
267 gives you up to 3% performance improvement on AMD F15h
268 machines (where it is enabled by default) for a
269 CPU-intensive style benchmark, and it can vary highly in
270 a microbenchmark depending on workload and compiler.
271
272 32: only for 32-bit processes
273 64: only for 64-bit processes
274 on: enable for both 32- and 64-bit processes
275 off: disable for both 32- and 64-bit processes
276
277 alloc_snapshot [FTRACE]
278 Allocate the ftrace snapshot buffer on boot up when the
279 main buffer is allocated. This is handy if debugging
280 and you need to use tracing_snapshot() on boot up, and
281 do not want to use tracing_snapshot_alloc() as it needs
282 to be done where GFP_KERNEL allocations are allowed.
283
284 amd_iommu= [HW,X86-64]
285 Pass parameters to the AMD IOMMU driver in the system.
286 Possible values are:
287 fullflush - enable flushing of IO/TLB entries when
288 they are unmapped. Otherwise they are
289 flushed before they will be reused, which
290 is a lot of faster
291 off - do not initialize any AMD IOMMU found in
292 the system
293 force_isolation - Force device isolation for all
294 devices. The IOMMU driver is not
295 allowed anymore to lift isolation
296 requirements as needed. This option
297 does not override iommu=pt
298
299 amd_iommu_dump= [HW,X86-64]
300 Enable AMD IOMMU driver option to dump the ACPI table
301 for AMD IOMMU. With this option enabled, AMD IOMMU
302 driver will print ACPI tables for AMD IOMMU during
303 IOMMU initialization.
304
305 amd_iommu_intr= [HW,X86-64]
306 Specifies one of the following AMD IOMMU interrupt
307 remapping modes:
308 legacy - Use legacy interrupt remapping mode.
309 vapic - Use virtual APIC mode, which allows IOMMU
310 to inject interrupts directly into guest.
311 This mode requires kvm-amd.avic=1.
312 (Default when IOMMU HW support is present.)
313
314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
316 Format: <a>,<b>
317 See also Documentation/input/joystick.txt
318
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
323
324 apc= [HW,SPARC]
325 Power management functions (SPARCstation-4/5 + deriv.)
326 Format: noidle
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
330
331 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
332 Change the output verbosity whilst booting
333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
336
337 apic_extnmi= [APIC,X86] External NMI delivery setting
338 Format: { bsp (default) | all | none }
339 bsp: External NMI is delivered only to CPU 0
340 all: External NMIs are broadcast to all CPUs as a
341 backup of CPU 0
342 none: External NMI is masked for all CPUs. This is
343 useful so that a dump capture kernel won't be
344 shot down by NMI
345
346 autoconf= [IPV6]
347 See Documentation/networking/ipv6.txt.
348
349 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
350 Limit apic dumping. The parameter defines the maximal
351 number of local apics being dumped. Also it is possible
352 to set it to "all" by meaning -- no limit here.
353 Format: { 1 (default) | 2 | ... | all }.
354 The parameter valid if only apic=debug or
355 apic=verbose is specified.
356 Example: apic=debug show_lapic=all
357
358 apm= [APM] Advanced Power Management
359 See header of arch/x86/kernel/apm_32.c.
360
361 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
362 Format: <io>,<irq>,<nodeID>
363
364 ataflop= [HW,M68k]
365
366 atarimouse= [HW,MOUSE] Atari Mouse
367
368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
370
371 atkbd.reset= [HW] Reset keyboard during initialization
372
373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
375
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 keyboards
378
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
381
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
384
385 audit= [KNL] Enable the audit sub-system
386 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
387 0 - kernel audit is disabled and can not be enabled
388 until the next reboot
389 unset - kernel audit is initialized but disabled and
390 will be fully enabled by the userspace auditd.
391 1 - kernel audit is initialized and partially enabled,
392 storing at most audit_backlog_limit messages in
393 RAM until it is fully enabled by the userspace
394 auditd.
395 Default: unset
396
397 audit_backlog_limit= [KNL] Set the audit queue size limit.
398 Format: <int> (must be >=0)
399 Default: 64
400
401 bau= [X86_UV] Enable the BAU on SGI UV. The default
402 behavior is to disable the BAU (i.e. bau=0).
403 Format: { "0" | "1" }
404 0 - Disable the BAU.
405 1 - Enable the BAU.
406 unset - Disable the BAU.
407
408 baycom_epp= [HW,AX25]
409 Format: <io>,<mode>
410
411 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
412 Format: <io>,<mode>
413 See header of drivers/net/hamradio/baycom_par.c.
414
415 baycom_ser_fdx= [HW,AX25]
416 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
417 Format: <io>,<irq>,<mode>[,<baud>]
418 See header of drivers/net/hamradio/baycom_ser_fdx.c.
419
420 baycom_ser_hdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
422 Format: <io>,<irq>,<mode>
423 See header of drivers/net/hamradio/baycom_ser_hdx.c.
424
425 blkdevparts= Manual partition parsing of block device(s) for
426 embedded devices based on command line input.
427 See Documentation/block/cmdline-partition.txt
428
429 boot_delay= Milliseconds to delay each printk during boot.
430 Values larger than 10 seconds (10000) are changed to
431 no delay (0).
432 Format: integer
433
434 bootmem_debug [KNL] Enable bootmem allocator debug messages.
435
436 bert_disable [ACPI]
437 Disable BERT OS support on buggy BIOSes.
438
439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
440 bttv.radio= Most important insmod options are available as
441 kernel args too.
442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
443 bttv.tuner=
444
445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
447 at a time.
448
449 c101= [NET] Moxa C101 synchronous serial card
450
451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
457
458 ca_keys= [KEYS] This parameter identifies a specific key(s) on
459 the system trusted keyring to be used for certificate
460 trust validation.
461 format: { id:<keyid> | builtin }
462
463 cca= [MIPS] Override the kernel pages' cache coherency
464 algorithm. Accepted values range from 0 to 7
465 inclusive. See arch/mips/include/asm/pgtable-bits.h
466 for platform specific values (SB1, Loongson3 and
467 others).
468
469 ccw_timeout_log [S390]
470 See Documentation/s390/CommonIO for details.
471
472 cgroup_disable= [KNL] Disable a particular controller
473 Format: {name of the controller(s) to disable}
474 The effects of cgroup_disable=foo are:
475 - foo isn't auto-mounted if you mount all cgroups in
476 a single hierarchy
477 - foo isn't visible as an individually mountable
478 subsystem
479 {Currently only "memory" controller deal with this and
480 cut the overhead, others just disable the usage. So
481 only cgroup_disable=memory is actually worthy}
482
483 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
484 Format: { controller[,controller...] | "all" }
485 Like cgroup_disable, but only applies to cgroup v1;
486 the blacklisted controllers remain available in cgroup2.
487
488 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
489 Format: <string>
490 nosocket -- Disable socket memory accounting.
491 nokmem -- Disable kernel memory accounting.
492
493 checkreqprot [SELINUX] Set initial checkreqprot flag value.
494 Format: { "0" | "1" }
495 See security/selinux/Kconfig help text.
496 0 -- check protection applied by kernel (includes
497 any implied execute protection).
498 1 -- check protection requested by application.
499 Default value is set via a kernel config option.
500 Value can be changed at runtime via
501 /selinux/checkreqprot.
502
503 cio_ignore= [S390]
504 See Documentation/s390/CommonIO for details.
505 clk_ignore_unused
506 [CLK]
507 Prevents the clock framework from automatically gating
508 clocks that have not been explicitly enabled by a Linux
509 device driver but are enabled in hardware at reset or
510 by the bootloader/firmware. Note that this does not
511 force such clocks to be always-on nor does it reserve
512 those clocks in any way. This parameter is useful for
513 debug and development, but should not be needed on a
514 platform with proper driver support. For more
515 information, see Documentation/clk.txt.
516
517 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
518 [Deprecated]
519 Forces specified clocksource (if available) to be used
520 when calculating gettimeofday(). If specified
521 clocksource is not available, it defaults to PIT.
522 Format: { pit | tsc | cyclone | pmtmr }
523
524 clocksource= Override the default clocksource
525 Format: <string>
526 Override the default clocksource and use the clocksource
527 with the name specified.
528 Some clocksource names to choose from, depending on
529 the platform:
530 [all] jiffies (this is the base, fallback clocksource)
531 [ACPI] acpi_pm
532 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
533 pxa_timer,timer3,32k_counter,timer0_1
534 [AVR32] avr32
535 [X86-32] pit,hpet,tsc;
536 scx200_hrt on Geode; cyclone on IBM x440
537 [MIPS] MIPS
538 [PARISC] cr16
539 [S390] tod
540 [SH] SuperH
541 [SPARC64] tick
542 [X86-64] hpet,tsc
543
544 clocksource.arm_arch_timer.evtstrm=
545 [ARM,ARM64]
546 Format: <bool>
547 Enable/disable the eventstream feature of the ARM
548 architected timer so that code using WFE-based polling
549 loops can be debugged more effectively on production
550 systems.
551
552 clocksource.arm_arch_timer.fsl-a008585=
553 [ARM64]
554 Format: <bool>
555 Enable/disable the workaround of Freescale/NXP
556 erratum A-008585. This can be useful for KVM
557 guests, if the guest device tree doesn't show the
558 erratum. If unspecified, the workaround is
559 enabled based on the device tree.
560
561 clearcpuid=BITNUM [X86]
562 Disable CPUID feature X for the kernel. See
563 arch/x86/include/asm/cpufeatures.h for the valid bit
564 numbers. Note the Linux specific bits are not necessarily
565 stable over kernel options, but the vendor specific
566 ones should be.
567 Also note that user programs calling CPUID directly
568 or using the feature without checking anything
569 will still see it. This just prevents it from
570 being used by the kernel or shown in /proc/cpuinfo.
571 Also note the kernel might malfunction if you disable
572 some critical bits.
573
574 cma=nn[MG]@[start[MG][-end[MG]]]
575 [ARM,X86,KNL]
576 Sets the size of kernel global memory area for
577 contiguous memory allocations and optionally the
578 placement constraint by the physical address range of
579 memory allocations. A value of 0 disables CMA
580 altogether. For more information, see
581 include/linux/dma-contiguous.h
582
583 cmo_free_hint= [PPC] Format: { yes | no }
584 Specify whether pages are marked as being inactive
585 when they are freed. This is used in CMO environments
586 to determine OS memory pressure for page stealing by
587 a hypervisor.
588 Default: yes
589
590 coherent_pool=nn[KMG] [ARM,KNL]
591 Sets the size of memory pool for coherent, atomic dma
592 allocations, by default set to 256K.
593
594 code_bytes [X86] How many bytes of object code to print
595 in an oops report.
596 Range: 0 - 8192
597 Default: 64
598
599 com20020= [HW,NET] ARCnet - COM20020 chipset
600 Format:
601 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
602
603 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
604 Format: <io>[,<irq>]
605
606 com90xx= [HW,NET]
607 ARCnet - COM90xx chipset (memory-mapped buffers)
608 Format: <io>[,<irq>[,<memstart>]]
609
610 condev= [HW,S390] console device
611 conmode=
612
613 console= [KNL] Output console device and options.
614
615 tty<n> Use the virtual console device <n>.
616
617 ttyS<n>[,options]
618 ttyUSB0[,options]
619 Use the specified serial port. The options are of
620 the form "bbbbpnf", where "bbbb" is the baud rate,
621 "p" is parity ("n", "o", or "e"), "n" is number of
622 bits, and "f" is flow control ("r" for RTS or
623 omit it). Default is "9600n8".
624
625 See Documentation/admin-guide/serial-console.rst for more
626 information. See
627 Documentation/networking/netconsole.txt for an
628 alternative.
629
630 uart[8250],io,<addr>[,options]
631 uart[8250],mmio,<addr>[,options]
632 uart[8250],mmio16,<addr>[,options]
633 uart[8250],mmio32,<addr>[,options]
634 uart[8250],0x<addr>[,options]
635 Start an early, polled-mode console on the 8250/16550
636 UART at the specified I/O port or MMIO address,
637 switching to the matching ttyS device later.
638 MMIO inter-register address stride is either 8-bit
639 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
640 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
641 to be equivalent to 'mmio'. 'options' are specified in
642 the same format described for ttyS above; if unspecified,
643 the h/w is not re-initialized.
644
645 hvc<n> Use the hypervisor console device <n>. This is for
646 both Xen and PowerPC hypervisors.
647
648 If the device connected to the port is not a TTY but a braille
649 device, prepend "brl," before the device type, for instance
650 console=brl,ttyS0
651 For now, only VisioBraille is supported.
652
653 consoleblank= [KNL] The console blank (screen saver) timeout in
654 seconds. Defaults to 10*60 = 10mins. A value of 0
655 disables the blank timer.
656
657 coredump_filter=
658 [KNL] Change the default value for
659 /proc/<pid>/coredump_filter.
660 See also Documentation/filesystems/proc.txt.
661
662 cpuidle.off=1 [CPU_IDLE]
663 disable the cpuidle sub-system
664
665 cpu_init_udelay=N
666 [X86] Delay for N microsec between assert and de-assert
667 of APIC INIT to start processors. This delay occurs
668 on every CPU online, such as boot, and resume from suspend.
669 Default: 10000
670
671 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
672 Format:
673 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
674
675 crashkernel=size[KMG][@offset[KMG]]
676 [KNL] Using kexec, Linux can switch to a 'crash kernel'
677 upon panic. This parameter reserves the physical
678 memory region [offset, offset + size] for that kernel
679 image. If '@offset' is omitted, then a suitable offset
680 is selected automatically. Check
681 Documentation/kdump/kdump.txt for further details.
682
683 crashkernel=range1:size1[,range2:size2,...][@offset]
684 [KNL] Same as above, but depends on the memory
685 in the running system. The syntax of range is
686 start-[end] where start and end are both
687 a memory unit (amount[KMG]). See also
688 Documentation/kdump/kdump.txt for an example.
689
690 crashkernel=size[KMG],high
691 [KNL, x86_64] range could be above 4G. Allow kernel
692 to allocate physical memory region from top, so could
693 be above 4G if system have more than 4G ram installed.
694 Otherwise memory region will be allocated below 4G, if
695 available.
696 It will be ignored if crashkernel=X is specified.
697 crashkernel=size[KMG],low
698 [KNL, x86_64] range under 4G. When crashkernel=X,high
699 is passed, kernel could allocate physical memory region
700 above 4G, that cause second kernel crash on system
701 that require some amount of low memory, e.g. swiotlb
702 requires at least 64M+32K low memory, also enough extra
703 low memory is needed to make sure DMA buffers for 32-bit
704 devices won't run out. Kernel would try to allocate at
705 at least 256M below 4G automatically.
706 This one let user to specify own low range under 4G
707 for second kernel instead.
708 0: to disable low allocation.
709 It will be ignored when crashkernel=X,high is not used
710 or memory reserved is below 4G.
711
712 cryptomgr.notests
713 [KNL] Disable crypto self-tests
714
715 cs89x0_dma= [HW,NET]
716 Format: <dma>
717
718 cs89x0_media= [HW,NET]
719 Format: { rj45 | aui | bnc }
720
721 dasd= [HW,NET]
722 See header of drivers/s390/block/dasd_devmap.c.
723
724 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
725 (one device per port)
726 Format: <port#>,<type>
727 See also Documentation/input/joystick-parport.txt
728
729 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
730 time. See Documentation/dynamic-debug-howto.txt for
731 details. Deprecated, see dyndbg.
732
733 debug [KNL] Enable kernel debugging (events log level).
734
735 debug_locks_verbose=
736 [KNL] verbose self-tests
737 Format=<0|1>
738 Print debugging info while doing the locking API
739 self-tests.
740 We default to 0 (no extra messages), setting it to
741 1 will print _a lot_ more information - normally
742 only useful to kernel developers.
743
744 debug_objects [KNL] Enable object debugging
745
746 no_debug_objects
747 [KNL] Disable object debugging
748
749 debug_guardpage_minorder=
750 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
751 parameter allows control of the order of pages that will
752 be intentionally kept free (and hence protected) by the
753 buddy allocator. Bigger value increase the probability
754 of catching random memory corruption, but reduce the
755 amount of memory for normal system use. The maximum
756 possible value is MAX_ORDER/2. Setting this parameter
757 to 1 or 2 should be enough to identify most random
758 memory corruption problems caused by bugs in kernel or
759 driver code when a CPU writes to (or reads from) a
760 random memory location. Note that there exists a class
761 of memory corruptions problems caused by buggy H/W or
762 F/W or by drivers badly programing DMA (basically when
763 memory is written at bus level and the CPU MMU is
764 bypassed) which are not detectable by
765 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
766 tracking down these problems.
767
768 debug_pagealloc=
769 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
770 parameter enables the feature at boot time. In
771 default, it is disabled. We can avoid allocating huge
772 chunk of memory for debug pagealloc if we don't enable
773 it at boot time and the system will work mostly same
774 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
775 on: enable the feature
776
777 debugpat [X86] Enable PAT debugging
778
779 decnet.addr= [HW,NET]
780 Format: <area>[,<node>]
781 See also Documentation/networking/decnet.txt.
782
783 default_hugepagesz=
784 [same as hugepagesz=] The size of the default
785 HugeTLB page size. This is the size represented by
786 the legacy /proc/ hugepages APIs, used for SHM, and
787 default size when mounting hugetlbfs filesystems.
788 Defaults to the default architecture's huge page size
789 if not specified.
790
791 dhash_entries= [KNL]
792 Set number of hash buckets for dentry cache.
793
794 disable_1tb_segments [PPC]
795 Disables the use of 1TB hash page table segments. This
796 causes the kernel to fall back to 256MB segments which
797 can be useful when debugging issues that require an SLB
798 miss to occur.
799
800 disable= [IPV6]
801 See Documentation/networking/ipv6.txt.
802
803 disable_radix [PPC]
804 Disable RADIX MMU mode on POWER9
805
806 disable_cpu_apicid= [X86,APIC,SMP]
807 Format: <int>
808 The number of initial APIC ID for the
809 corresponding CPU to be disabled at boot,
810 mostly used for the kdump 2nd kernel to
811 disable BSP to wake up multiple CPUs without
812 causing system reset or hang due to sending
813 INIT from AP to BSP.
814
815 disable_ddw [PPC/PSERIES]
816 Disable Dynamic DMA Window support. Use this if
817 to workaround buggy firmware.
818
819 disable_ipv6= [IPV6]
820 See Documentation/networking/ipv6.txt.
821
822 disable_mtrr_cleanup [X86]
823 The kernel tries to adjust MTRR layout from continuous
824 to discrete, to make X server driver able to add WB
825 entry later. This parameter disables that.
826
827 disable_mtrr_trim [X86, Intel and AMD only]
828 By default the kernel will trim any uncacheable
829 memory out of your available memory pool based on
830 MTRR settings. This parameter disables that behavior,
831 possibly causing your machine to run very slowly.
832
833 disable_timer_pin_1 [X86]
834 Disable PIN 1 of APIC timer
835 Can be useful to work around chipset bugs.
836
837 dis_ucode_ldr [X86] Disable the microcode loader.
838
839 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
840 this option disables the debugging code at boot.
841
842 dma_debug_entries=<number>
843 This option allows to tune the number of preallocated
844 entries for DMA-API debugging code. One entry is
845 required per DMA-API allocation. Use this if the
846 DMA-API debugging code disables itself because the
847 architectural default is too low.
848
849 dma_debug_driver=<driver_name>
850 With this option the DMA-API debugging driver
851 filter feature can be enabled at boot time. Just
852 pass the driver to filter for as the parameter.
853 The filter can be disabled or changed to another
854 driver later using sysfs.
855
856 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
857 Broken monitors, graphic adapters, KVMs and EDIDless
858 panels may send no or incorrect EDID data sets.
859 This parameter allows to specify an EDID data sets
860 in the /lib/firmware directory that are used instead.
861 Generic built-in EDID data sets are used, if one of
862 edid/1024x768.bin, edid/1280x1024.bin,
863 edid/1680x1050.bin, or edid/1920x1080.bin is given
864 and no file with the same name exists. Details and
865 instructions how to build your own EDID data are
866 available in Documentation/EDID/HOWTO.txt. An EDID
867 data set will only be used for a particular connector,
868 if its name and a colon are prepended to the EDID
869 name. Each connector may use a unique EDID data
870 set by separating the files with a comma. An EDID
871 data set with no connector name will be used for
872 any connectors not explicitly specified.
873
874 dscc4.setup= [NET]
875
876 dump_apple_properties [X86]
877 Dump name and content of EFI device properties on
878 x86 Macs. Useful for driver authors to determine
879 what data is available or for reverse-engineering.
880
881 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
882 module.dyndbg[="val"]
883 Enable debug messages at boot time. See
884 Documentation/dynamic-debug-howto.txt for details.
885
886 nompx [X86] Disables Intel Memory Protection Extensions.
887 See Documentation/x86/intel_mpx.txt for more
888 information about the feature.
889
890 nopku [X86] Disable Memory Protection Keys CPU feature found
891 in some Intel CPUs.
892
893 module.async_probe [KNL]
894 Enable asynchronous probe on this module.
895
896 early_ioremap_debug [KNL]
897 Enable debug messages in early_ioremap support. This
898 is useful for tracking down temporary early mappings
899 which are not unmapped.
900
901 earlycon= [KNL] Output early console device and options.
902
903 When used with no options, the early console is
904 determined by the stdout-path property in device
905 tree's chosen node.
906
907 cdns,<addr>[,options]
908 Start an early, polled-mode console on a Cadence
909 (xuartps) serial port at the specified address. Only
910 supported option is baud rate. If baud rate is not
911 specified, the serial port must already be setup and
912 configured.
913
914 uart[8250],io,<addr>[,options]
915 uart[8250],mmio,<addr>[,options]
916 uart[8250],mmio32,<addr>[,options]
917 uart[8250],mmio32be,<addr>[,options]
918 uart[8250],0x<addr>[,options]
919 Start an early, polled-mode console on the 8250/16550
920 UART at the specified I/O port or MMIO address.
921 MMIO inter-register address stride is either 8-bit
922 (mmio) or 32-bit (mmio32 or mmio32be).
923 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
924 to be equivalent to 'mmio'. 'options' are specified
925 in the same format described for "console=ttyS<n>"; if
926 unspecified, the h/w is not initialized.
927
928 pl011,<addr>
929 pl011,mmio32,<addr>
930 Start an early, polled-mode console on a pl011 serial
931 port at the specified address. The pl011 serial port
932 must already be setup and configured. Options are not
933 yet supported. If 'mmio32' is specified, then only
934 the driver will use only 32-bit accessors to read/write
935 the device registers.
936
937 meson,<addr>
938 Start an early, polled-mode console on a meson serial
939 port at the specified address. The serial port must
940 already be setup and configured. Options are not yet
941 supported.
942
943 msm_serial,<addr>
944 Start an early, polled-mode console on an msm serial
945 port at the specified address. The serial port
946 must already be setup and configured. Options are not
947 yet supported.
948
949 msm_serial_dm,<addr>
950 Start an early, polled-mode console on an msm serial
951 dm port at the specified address. The serial port
952 must already be setup and configured. Options are not
953 yet supported.
954
955 smh Use ARM semihosting calls for early console.
956
957 s3c2410,<addr>
958 s3c2412,<addr>
959 s3c2440,<addr>
960 s3c6400,<addr>
961 s5pv210,<addr>
962 exynos4210,<addr>
963 Use early console provided by serial driver available
964 on Samsung SoCs, requires selecting proper type and
965 a correct base address of the selected UART port. The
966 serial port must already be setup and configured.
967 Options are not yet supported.
968
969 lpuart,<addr>
970 lpuart32,<addr>
971 Use early console provided by Freescale LP UART driver
972 found on Freescale Vybrid and QorIQ LS1021A processors.
973 A valid base address must be provided, and the serial
974 port must already be setup and configured.
975
976 armada3700_uart,<addr>
977 Start an early, polled-mode console on the
978 Armada 3700 serial port at the specified
979 address. The serial port must already be setup
980 and configured. Options are not yet supported.
981
982 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
983 earlyprintk=vga
984 earlyprintk=efi
985 earlyprintk=xen
986 earlyprintk=serial[,ttySn[,baudrate]]
987 earlyprintk=serial[,0x...[,baudrate]]
988 earlyprintk=ttySn[,baudrate]
989 earlyprintk=dbgp[debugController#]
990 earlyprintk=pciserial,bus:device.function[,baudrate]
991
992 earlyprintk is useful when the kernel crashes before
993 the normal console is initialized. It is not enabled by
994 default because it has some cosmetic problems.
995
996 Append ",keep" to not disable it when the real console
997 takes over.
998
999 Only one of vga, efi, serial, or usb debug port can
1000 be used at a time.
1001
1002 Currently only ttyS0 and ttyS1 may be specified by
1003 name. Other I/O ports may be explicitly specified
1004 on some architectures (x86 and arm at least) by
1005 replacing ttySn with an I/O port address, like this:
1006 earlyprintk=serial,0x1008,115200
1007 You can find the port for a given device in
1008 /proc/tty/driver/serial:
1009 2: uart:ST16650V2 port:00001008 irq:18 ...
1010
1011 Interaction with the standard serial driver is not
1012 very good.
1013
1014 The VGA and EFI output is eventually overwritten by
1015 the real console.
1016
1017 The xen output can only be used by Xen PV guests.
1018
1019 edac_report= [HW,EDAC] Control how to report EDAC event
1020 Format: {"on" | "off" | "force"}
1021 on: enable EDAC to report H/W event. May be overridden
1022 by other higher priority error reporting module.
1023 off: disable H/W event reporting through EDAC.
1024 force: enforce the use of EDAC to report H/W event.
1025 default: on.
1026
1027 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1028 ekgdboc=kbd
1029
1030 This is designed to be used in conjunction with
1031 the boot argument: earlyprintk=vga
1032
1033 edd= [EDD]
1034 Format: {"off" | "on" | "skip[mbr]"}
1035
1036 efi= [EFI]
1037 Format: { "old_map", "nochunk", "noruntime", "debug" }
1038 old_map [X86-64]: switch to the old ioremap-based EFI
1039 runtime services mapping. 32-bit still uses this one by
1040 default.
1041 nochunk: disable reading files in "chunks" in the EFI
1042 boot stub, as chunking can cause problems with some
1043 firmware implementations.
1044 noruntime : disable EFI runtime services support
1045 debug: enable misc debug output
1046
1047 efi_no_storage_paranoia [EFI; X86]
1048 Using this parameter you can use more than 50% of
1049 your efi variable storage. Use this parameter only if
1050 you are really sure that your UEFI does sane gc and
1051 fulfills the spec otherwise your board may brick.
1052
1053 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1054 Add arbitrary attribute to specific memory range by
1055 updating original EFI memory map.
1056 Region of memory which aa attribute is added to is
1057 from ss to ss+nn.
1058 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1059 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1060 attribute is added to range 0x100000000-0x180000000 and
1061 0x10a0000000-0x1120000000.
1062
1063 Using this parameter you can do debugging of EFI memmap
1064 related feature. For example, you can do debugging of
1065 Address Range Mirroring feature even if your box
1066 doesn't support it.
1067
1068 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1069 that is to be dynamically loaded by Linux. If there are
1070 multiple variables with the same name but with different
1071 vendor GUIDs, all of them will be loaded. See
1072 Documentation/acpi/ssdt-overlays.txt for details.
1073
1074
1075 eisa_irq_edge= [PARISC,HW]
1076 See header of drivers/parisc/eisa.c.
1077
1078 elanfreq= [X86-32]
1079 See comment before function elanfreq_setup() in
1080 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1081
1082 elevator= [IOSCHED]
1083 Format: {"cfq" | "deadline" | "noop"}
1084 See Documentation/block/cfq-iosched.txt and
1085 Documentation/block/deadline-iosched.txt for details.
1086
1087 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1088 Specifies physical address of start of kernel core
1089 image elf header and optionally the size. Generally
1090 kexec loader will pass this option to capture kernel.
1091 See Documentation/kdump/kdump.txt for details.
1092
1093 enable_mtrr_cleanup [X86]
1094 The kernel tries to adjust MTRR layout from continuous
1095 to discrete, to make X server driver able to add WB
1096 entry later. This parameter enables that.
1097
1098 enable_timer_pin_1 [X86]
1099 Enable PIN 1 of APIC timer
1100 Can be useful to work around chipset bugs
1101 (in particular on some ATI chipsets).
1102 The kernel tries to set a reasonable default.
1103
1104 enforcing [SELINUX] Set initial enforcing status.
1105 Format: {"0" | "1"}
1106 See security/selinux/Kconfig help text.
1107 0 -- permissive (log only, no denials).
1108 1 -- enforcing (deny and log).
1109 Default value is 0.
1110 Value can be changed at runtime via /selinux/enforce.
1111
1112 erst_disable [ACPI]
1113 Disable Error Record Serialization Table (ERST)
1114 support.
1115
1116 ether= [HW,NET] Ethernet cards parameters
1117 This option is obsoleted by the "netdev=" option, which
1118 has equivalent usage. See its documentation for details.
1119
1120 evm= [EVM]
1121 Format: { "fix" }
1122 Permit 'security.evm' to be updated regardless of
1123 current integrity status.
1124
1125 failslab=
1126 fail_page_alloc=
1127 fail_make_request=[KNL]
1128 General fault injection mechanism.
1129 Format: <interval>,<probability>,<space>,<times>
1130 See also Documentation/fault-injection/.
1131
1132 floppy= [HW]
1133 See Documentation/blockdev/floppy.txt.
1134
1135 force_pal_cache_flush
1136 [IA-64] Avoid check_sal_cache_flush which may hang on
1137 buggy SAL_CACHE_FLUSH implementations. Using this
1138 parameter will force ia64_sal_cache_flush to call
1139 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1140
1141 forcepae [X86-32]
1142 Forcefully enable Physical Address Extension (PAE).
1143 Many Pentium M systems disable PAE but may have a
1144 functionally usable PAE implementation.
1145 Warning: use of this parameter will taint the kernel
1146 and may cause unknown problems.
1147
1148 ftrace=[tracer]
1149 [FTRACE] will set and start the specified tracer
1150 as early as possible in order to facilitate early
1151 boot debugging.
1152
1153 ftrace_dump_on_oops[=orig_cpu]
1154 [FTRACE] will dump the trace buffers on oops.
1155 If no parameter is passed, ftrace will dump
1156 buffers of all CPUs, but if you pass orig_cpu, it will
1157 dump only the buffer of the CPU that triggered the
1158 oops.
1159
1160 ftrace_filter=[function-list]
1161 [FTRACE] Limit the functions traced by the function
1162 tracer at boot up. function-list is a comma separated
1163 list of functions. This list can be changed at run
1164 time by the set_ftrace_filter file in the debugfs
1165 tracing directory.
1166
1167 ftrace_notrace=[function-list]
1168 [FTRACE] Do not trace the functions specified in
1169 function-list. This list can be changed at run time
1170 by the set_ftrace_notrace file in the debugfs
1171 tracing directory.
1172
1173 ftrace_graph_filter=[function-list]
1174 [FTRACE] Limit the top level callers functions traced
1175 by the function graph tracer at boot up.
1176 function-list is a comma separated list of functions
1177 that can be changed at run time by the
1178 set_graph_function file in the debugfs tracing directory.
1179
1180 ftrace_graph_notrace=[function-list]
1181 [FTRACE] Do not trace from the functions specified in
1182 function-list. This list is a comma separated list of
1183 functions that can be changed at run time by the
1184 set_graph_notrace file in the debugfs tracing directory.
1185
1186 gamecon.map[2|3]=
1187 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1188 support via parallel port (up to 5 devices per port)
1189 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1190 See also Documentation/input/joystick-parport.txt
1191
1192 gamma= [HW,DRM]
1193
1194 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1195 Format: off | on
1196 default: on
1197
1198 gcov_persist= [GCOV] When non-zero (default), profiling data for
1199 kernel modules is saved and remains accessible via
1200 debugfs, even when the module is unloaded/reloaded.
1201 When zero, profiling data is discarded and associated
1202 debugfs files are removed at module unload time.
1203
1204 goldfish [X86] Enable the goldfish android emulator platform.
1205 Don't use this when you are not running on the
1206 android emulator
1207
1208 gpt [EFI] Forces disk with valid GPT signature but
1209 invalid Protective MBR to be treated as GPT. If the
1210 primary GPT is corrupted, it enables the backup/alternate
1211 GPT to be used instead.
1212
1213 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1214 the "Enable 0" bit of the configuration register.
1215 Format: 0 | 1
1216 Default: 0
1217 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1218 the "Enable 0" bit of the configuration register.
1219 Format: 0 | 1
1220 Default: 0
1221 grcan.select= [HW] Select which physical interface to use.
1222 Format: 0 | 1
1223 Default: 0
1224 grcan.txsize= [HW] Sets the size of the tx buffer.
1225 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1226 Default: 1024
1227 grcan.rxsize= [HW] Sets the size of the rx buffer.
1228 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1229 Default: 1024
1230
1231 gpio-mockup.gpio_mockup_ranges
1232 [HW] Sets the ranges of gpiochip of for this device.
1233 Format: <start1>,<end1>,<start2>,<end2>...
1234
1235 hardlockup_all_cpu_backtrace=
1236 [KNL] Should the hard-lockup detector generate
1237 backtraces on all cpus.
1238 Format: <integer>
1239
1240 hashdist= [KNL,NUMA] Large hashes allocated during boot
1241 are distributed across NUMA nodes. Defaults on
1242 for 64-bit NUMA, off otherwise.
1243 Format: 0 | 1 (for off | on)
1244
1245 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1246
1247 hd= [EIDE] (E)IDE hard drive subsystem geometry
1248 Format: <cyl>,<head>,<sect>
1249
1250 hest_disable [ACPI]
1251 Disable Hardware Error Source Table (HEST) support;
1252 corresponding firmware-first mode error processing
1253 logic will be disabled.
1254
1255 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1256 size of <nn>. This works even on boxes that have no
1257 highmem otherwise. This also works to reduce highmem
1258 size on bigger boxes.
1259
1260 highres= [KNL] Enable/disable high resolution timer mode.
1261 Valid parameters: "on", "off"
1262 Default: "on"
1263
1264 hisax= [HW,ISDN]
1265 See Documentation/isdn/README.HiSax.
1266
1267 hlt [BUGS=ARM,SH]
1268
1269 hpet= [X86-32,HPET] option to control HPET usage
1270 Format: { enable (default) | disable | force |
1271 verbose }
1272 disable: disable HPET and use PIT instead
1273 force: allow force enabled of undocumented chips (ICH4,
1274 VIA, nVidia)
1275 verbose: show contents of HPET registers during setup
1276
1277 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1278 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1279
1280 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1281 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1282 On x86-64 and powerpc, this option can be specified
1283 multiple times interleaved with hugepages= to reserve
1284 huge pages of different sizes. Valid pages sizes on
1285 x86-64 are 2M (when the CPU supports "pse") and 1G
1286 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1287
1288 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1289 terminal devices. Valid values: 0..8
1290 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1291 If specified, z/VM IUCV HVC accepts connections
1292 from listed z/VM user IDs only.
1293
1294 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1295 hardware thread id mappings.
1296 Format: <cpu>:<hwthread>
1297
1298 keep_bootcon [KNL]
1299 Do not unregister boot console at start. This is only
1300 useful for debugging when something happens in the window
1301 between unregistering the boot console and initializing
1302 the real console.
1303
1304 i2c_bus= [HW] Override the default board specific I2C bus speed
1305 or register an additional I2C bus that is not
1306 registered from board initialization code.
1307 Format:
1308 <bus_id>,<clkrate>
1309
1310 i8042.debug [HW] Toggle i8042 debug mode
1311 i8042.unmask_kbd_data
1312 [HW] Enable printing of interrupt data from the KBD port
1313 (disabled by default, and as a pre-condition
1314 requires that i8042.debug=1 be enabled)
1315 i8042.direct [HW] Put keyboard port into non-translated mode
1316 i8042.dumbkbd [HW] Pretend that controller can only read data from
1317 keyboard and cannot control its state
1318 (Don't attempt to blink the leds)
1319 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1320 i8042.nokbd [HW] Don't check/create keyboard port
1321 i8042.noloop [HW] Disable the AUX Loopback command while probing
1322 for the AUX port
1323 i8042.nomux [HW] Don't check presence of an active multiplexing
1324 controller
1325 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1326 controllers
1327 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1328 i8042.reset [HW] Reset the controller during init, cleanup and
1329 suspend-to-ram transitions, only during s2r
1330 transitions, or never reset
1331 Format: { 1 | Y | y | 0 | N | n }
1332 1, Y, y: always reset controller
1333 0, N, n: don't ever reset controller
1334 Default: only on s2r transitions on x86; most other
1335 architectures force reset to be always executed
1336 i8042.unlock [HW] Unlock (ignore) the keylock
1337 i8042.kbdreset [HW] Reset device connected to KBD port
1338
1339 i810= [HW,DRM]
1340
1341 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1342 indicates that the driver is running on unsupported
1343 hardware.
1344 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1345 does not match list of supported models.
1346 i8k.power_status
1347 [HW] Report power status in /proc/i8k
1348 (disabled by default)
1349 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1350 capability is set.
1351
1352 i915.invert_brightness=
1353 [DRM] Invert the sense of the variable that is used to
1354 set the brightness of the panel backlight. Normally a
1355 brightness value of 0 indicates backlight switched off,
1356 and the maximum of the brightness value sets the backlight
1357 to maximum brightness. If this parameter is set to 0
1358 (default) and the machine requires it, or this parameter
1359 is set to 1, a brightness value of 0 sets the backlight
1360 to maximum brightness, and the maximum of the brightness
1361 value switches the backlight off.
1362 -1 -- never invert brightness
1363 0 -- machine default
1364 1 -- force brightness inversion
1365
1366 icn= [HW,ISDN]
1367 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1368
1369 ide-core.nodma= [HW] (E)IDE subsystem
1370 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1371 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1372 .cdrom .chs .ignore_cable are additional options
1373 See Documentation/ide/ide.txt.
1374
1375 ide-generic.probe-mask= [HW] (E)IDE subsystem
1376 Format: <int>
1377 Probe mask for legacy ISA IDE ports. Depending on
1378 platform up to 6 ports are supported, enabled by
1379 setting corresponding bits in the mask to 1. The
1380 default value is 0x0, which has a special meaning.
1381 On systems that have PCI, it triggers scanning the
1382 PCI bus for the first and the second port, which
1383 are then probed. On systems without PCI the value
1384 of 0x0 enables probing the two first ports as if it
1385 was 0x3.
1386
1387 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1388 Claim all unknown PCI IDE storage controllers.
1389
1390 idle= [X86]
1391 Format: idle=poll, idle=halt, idle=nomwait
1392 Poll forces a polling idle loop that can slightly
1393 improve the performance of waking up a idle CPU, but
1394 will use a lot of power and make the system run hot.
1395 Not recommended.
1396 idle=halt: Halt is forced to be used for CPU idle.
1397 In such case C2/C3 won't be used again.
1398 idle=nomwait: Disable mwait for CPU C-states
1399
1400 ieee754= [MIPS] Select IEEE Std 754 conformance mode
1401 Format: { strict | legacy | 2008 | relaxed }
1402 Default: strict
1403
1404 Choose which programs will be accepted for execution
1405 based on the IEEE 754 NaN encoding(s) supported by
1406 the FPU and the NaN encoding requested with the value
1407 of an ELF file header flag individually set by each
1408 binary. Hardware implementations are permitted to
1409 support either or both of the legacy and the 2008 NaN
1410 encoding mode.
1411
1412 Available settings are as follows:
1413 strict accept binaries that request a NaN encoding
1414 supported by the FPU
1415 legacy only accept legacy-NaN binaries, if supported
1416 by the FPU
1417 2008 only accept 2008-NaN binaries, if supported
1418 by the FPU
1419 relaxed accept any binaries regardless of whether
1420 supported by the FPU
1421
1422 The FPU emulator is always able to support both NaN
1423 encodings, so if no FPU hardware is present or it has
1424 been disabled with 'nofpu', then the settings of
1425 'legacy' and '2008' strap the emulator accordingly,
1426 'relaxed' straps the emulator for both legacy-NaN and
1427 2008-NaN, whereas 'strict' enables legacy-NaN only on
1428 legacy processors and both NaN encodings on MIPS32 or
1429 MIPS64 CPUs.
1430
1431 The setting for ABS.fmt/NEG.fmt instruction execution
1432 mode generally follows that for the NaN encoding,
1433 except where unsupported by hardware.
1434
1435 ignore_loglevel [KNL]
1436 Ignore loglevel setting - this will print /all/
1437 kernel messages to the console. Useful for debugging.
1438 We also add it as printk module parameter, so users
1439 could change it dynamically, usually by
1440 /sys/module/printk/parameters/ignore_loglevel.
1441
1442 ignore_rlimit_data
1443 Ignore RLIMIT_DATA setting for data mappings,
1444 print warning at first misuse. Can be changed via
1445 /sys/module/kernel/parameters/ignore_rlimit_data.
1446
1447 ihash_entries= [KNL]
1448 Set number of hash buckets for inode cache.
1449
1450 ima_appraise= [IMA] appraise integrity measurements
1451 Format: { "off" | "enforce" | "fix" | "log" }
1452 default: "enforce"
1453
1454 ima_appraise_tcb [IMA]
1455 The builtin appraise policy appraises all files
1456 owned by uid=0.
1457
1458 ima_canonical_fmt [IMA]
1459 Use the canonical format for the binary runtime
1460 measurements, instead of host native format.
1461
1462 ima_hash= [IMA]
1463 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1464 | sha512 | ... }
1465 default: "sha1"
1466
1467 The list of supported hash algorithms is defined
1468 in crypto/hash_info.h.
1469
1470 ima_policy= [IMA]
1471 The builtin measurement policy to load during IMA
1472 setup. Specyfing "tcb" as the value, measures all
1473 programs exec'd, files mmap'd for exec, and all files
1474 opened with the read mode bit set by either the
1475 effective uid (euid=0) or uid=0.
1476 Format: "tcb"
1477
1478 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1479 Load a policy which meets the needs of the Trusted
1480 Computing Base. This means IMA will measure all
1481 programs exec'd, files mmap'd for exec, and all files
1482 opened for read by uid=0.
1483
1484 ima_template= [IMA]
1485 Select one of defined IMA measurements template formats.
1486 Formats: { "ima" | "ima-ng" | "ima-sig" }
1487 Default: "ima-ng"
1488
1489 ima_template_fmt=
1490 [IMA] Define a custom template format.
1491 Format: { "field1|...|fieldN" }
1492
1493 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1494 Format: <min_file_size>
1495 Set the minimal file size for using asynchronous hash.
1496 If left unspecified, ahash usage is disabled.
1497
1498 ahash performance varies for different data sizes on
1499 different crypto accelerators. This option can be used
1500 to achieve the best performance for a particular HW.
1501
1502 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1503 Format: <bufsize>
1504 Set hashing buffer size. Default: 4k.
1505
1506 ahash performance varies for different chunk sizes on
1507 different crypto accelerators. This option can be used
1508 to achieve best performance for particular HW.
1509
1510 init= [KNL]
1511 Format: <full_path>
1512 Run specified binary instead of /sbin/init as init
1513 process.
1514
1515 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1516 for working out where the kernel is dying during
1517 startup.
1518
1519 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1520 initcall functions. Useful for debugging built-in
1521 modules and initcalls.
1522
1523 initrd= [BOOT] Specify the location of the initial ramdisk
1524
1525 init_pkru= [x86] Specify the default memory protection keys rights
1526 register contents for all processes. 0x55555554 by
1527 default (disallow access to all but pkey 0). Can
1528 override in debugfs after boot.
1529
1530 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1531 Format: <irq>
1532
1533 int_pln_enable [x86] Enable power limit notification interrupt
1534
1535 integrity_audit=[IMA]
1536 Format: { "0" | "1" }
1537 0 -- basic integrity auditing messages. (Default)
1538 1 -- additional integrity auditing messages.
1539
1540 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1541 on
1542 Enable intel iommu driver.
1543 off
1544 Disable intel iommu driver.
1545 igfx_off [Default Off]
1546 By default, gfx is mapped as normal device. If a gfx
1547 device has a dedicated DMAR unit, the DMAR unit is
1548 bypassed by not enabling DMAR with this option. In
1549 this case, gfx device will use physical address for
1550 DMA.
1551 forcedac [x86_64]
1552 With this option iommu will not optimize to look
1553 for io virtual address below 32-bit forcing dual
1554 address cycle on pci bus for cards supporting greater
1555 than 32-bit addressing. The default is to look
1556 for translation below 32-bit and if not available
1557 then look in the higher range.
1558 strict [Default Off]
1559 With this option on every unmap_single operation will
1560 result in a hardware IOTLB flush operation as opposed
1561 to batching them for performance.
1562 sp_off [Default Off]
1563 By default, super page will be supported if Intel IOMMU
1564 has the capability. With this option, super page will
1565 not be supported.
1566 ecs_off [Default Off]
1567 By default, extended context tables will be supported if
1568 the hardware advertises that it has support both for the
1569 extended tables themselves, and also PASID support. With
1570 this option set, extended tables will not be used even
1571 on hardware which claims to support them.
1572
1573 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1574 0 disables intel_idle and fall back on acpi_idle.
1575 1 to 9 specify maximum depth of C-state.
1576
1577 intel_pstate= [X86]
1578 disable
1579 Do not enable intel_pstate as the default
1580 scaling driver for the supported processors
1581 passive
1582 Use intel_pstate as a scaling driver, but configure it
1583 to work with generic cpufreq governors (instead of
1584 enabling its internal governor). This mode cannot be
1585 used along with the hardware-managed P-states (HWP)
1586 feature.
1587 force
1588 Enable intel_pstate on systems that prohibit it by default
1589 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1590 instead of acpi-cpufreq may disable platform features, such
1591 as thermal controls and power capping, that rely on ACPI
1592 P-States information being indicated to OSPM and therefore
1593 should be used with caution. This option does not work with
1594 processors that aren't supported by the intel_pstate driver
1595 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1596 no_hwp
1597 Do not enable hardware P state control (HWP)
1598 if available.
1599 hwp_only
1600 Only load intel_pstate on systems which support
1601 hardware P state control (HWP) if available.
1602 support_acpi_ppc
1603 Enforce ACPI _PPC performance limits. If the Fixed ACPI
1604 Description Table, specifies preferred power management
1605 profile as "Enterprise Server" or "Performance Server",
1606 then this feature is turned on by default.
1607 per_cpu_perf_limits
1608 Allow per-logical-CPU P-State performance control limits using
1609 cpufreq sysfs interface
1610
1611 intremap= [X86-64, Intel-IOMMU]
1612 on enable Interrupt Remapping (default)
1613 off disable Interrupt Remapping
1614 nosid disable Source ID checking
1615 no_x2apic_optout
1616 BIOS x2APIC opt-out request will be ignored
1617 nopost disable Interrupt Posting
1618
1619 iomem= Disable strict checking of access to MMIO memory
1620 strict regions from userspace.
1621 relaxed
1622
1623 iommu= [x86]
1624 off
1625 force
1626 noforce
1627 biomerge
1628 panic
1629 nopanic
1630 merge
1631 nomerge
1632 forcesac
1633 soft
1634 pt [x86, IA-64]
1635 nobypass [PPC/POWERNV]
1636 Disable IOMMU bypass, using IOMMU for PCI devices.
1637
1638
1639 io7= [HW] IO7 for Marvel based alpha systems
1640 See comment before marvel_specify_io7 in
1641 arch/alpha/kernel/core_marvel.c.
1642
1643 io_delay= [X86] I/O delay method
1644 0x80
1645 Standard port 0x80 based delay
1646 0xed
1647 Alternate port 0xed based delay (needed on some systems)
1648 udelay
1649 Simple two microseconds delay
1650 none
1651 No delay
1652
1653 ip= [IP_PNP]
1654 See Documentation/filesystems/nfs/nfsroot.txt.
1655
1656 irqaffinity= [SMP] Set the default irq affinity mask
1657 The argument is a cpu list, as described above.
1658
1659 irqfixup [HW]
1660 When an interrupt is not handled search all handlers
1661 for it. Intended to get systems with badly broken
1662 firmware running.
1663
1664 irqpoll [HW]
1665 When an interrupt is not handled search all handlers
1666 for it. Also check all handlers each timer
1667 interrupt. Intended to get systems with badly broken
1668 firmware running.
1669
1670 isapnp= [ISAPNP]
1671 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1672
1673 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1674 The argument is a cpu list, as described above.
1675
1676 This option can be used to specify one or more CPUs
1677 to isolate from the general SMP balancing and scheduling
1678 algorithms. You can move a process onto or off an
1679 "isolated" CPU via the CPU affinity syscalls or cpuset.
1680 <cpu number> begins at 0 and the maximum value is
1681 "number of CPUs in system - 1".
1682
1683 This option is the preferred way to isolate CPUs. The
1684 alternative -- manually setting the CPU mask of all
1685 tasks in the system -- can cause problems and
1686 suboptimal load balancer performance.
1687
1688 iucv= [HW,NET]
1689
1690 ivrs_ioapic [HW,X86_64]
1691 Provide an override to the IOAPIC-ID<->DEVICE-ID
1692 mapping provided in the IVRS ACPI table. For
1693 example, to map IOAPIC-ID decimal 10 to
1694 PCI device 00:14.0 write the parameter as:
1695 ivrs_ioapic[10]=00:14.0
1696
1697 ivrs_hpet [HW,X86_64]
1698 Provide an override to the HPET-ID<->DEVICE-ID
1699 mapping provided in the IVRS ACPI table. For
1700 example, to map HPET-ID decimal 0 to
1701 PCI device 00:14.0 write the parameter as:
1702 ivrs_hpet[0]=00:14.0
1703
1704 ivrs_acpihid [HW,X86_64]
1705 Provide an override to the ACPI-HID:UID<->DEVICE-ID
1706 mapping provided in the IVRS ACPI table. For
1707 example, to map UART-HID:UID AMD0020:0 to
1708 PCI device 00:14.5 write the parameter as:
1709 ivrs_acpihid[00:14.5]=AMD0020:0
1710
1711 js= [HW,JOY] Analog joystick
1712 See Documentation/input/joystick.txt.
1713
1714 nokaslr [KNL]
1715 When CONFIG_RANDOMIZE_BASE is set, this disables
1716 kernel and module base offset ASLR (Address Space
1717 Layout Randomization).
1718
1719 keepinitrd [HW,ARM]
1720
1721 kernelcore= [KNL,X86,IA-64,PPC]
1722 Format: nn[KMGTPE] | "mirror"
1723 This parameter
1724 specifies the amount of memory usable by the kernel
1725 for non-movable allocations. The requested amount is
1726 spread evenly throughout all nodes in the system. The
1727 remaining memory in each node is used for Movable
1728 pages. In the event, a node is too small to have both
1729 kernelcore and Movable pages, kernelcore pages will
1730 take priority and other nodes will have a larger number
1731 of Movable pages. The Movable zone is used for the
1732 allocation of pages that may be reclaimed or moved
1733 by the page migration subsystem. This means that
1734 HugeTLB pages may not be allocated from this zone.
1735 Note that allocations like PTEs-from-HighMem still
1736 use the HighMem zone if it exists, and the Normal
1737 zone if it does not.
1738
1739 Instead of specifying the amount of memory (nn[KMGTPE]),
1740 you can specify "mirror" option. In case "mirror"
1741 option is specified, mirrored (reliable) memory is used
1742 for non-movable allocations and remaining memory is used
1743 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1744 so you can NOT specify nn[KMGTPE] and "mirror" at the same
1745 time.
1746
1747 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1748 Format: <Controller#>[,poll interval]
1749 The controller # is the number of the ehci usb debug
1750 port as it is probed via PCI. The poll interval is
1751 optional and is the number seconds in between
1752 each poll cycle to the debug port in case you need
1753 the functionality for interrupting the kernel with
1754 gdb or control-c on the dbgp connection. When
1755 not using this parameter you use sysrq-g to break into
1756 the kernel debugger.
1757
1758 kgdboc= [KGDB,HW] kgdb over consoles.
1759 Requires a tty driver that supports console polling,
1760 or a supported polling keyboard driver (non-usb).
1761 Serial only format: <serial_device>[,baud]
1762 keyboard only format: kbd
1763 keyboard and serial format: kbd,<serial_device>[,baud]
1764 Optional Kernel mode setting:
1765 kms, kbd format: kms,kbd
1766 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1767
1768 kgdbwait [KGDB] Stop kernel execution and enter the
1769 kernel debugger at the earliest opportunity.
1770
1771 kmac= [MIPS] korina ethernet MAC address.
1772 Configure the RouterBoard 532 series on-chip
1773 Ethernet adapter MAC address.
1774
1775 kmemleak= [KNL] Boot-time kmemleak enable/disable
1776 Valid arguments: on, off
1777 Default: on
1778 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1779 the default is off.
1780
1781 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1782 Valid arguments: 0, 1, 2
1783 kmemcheck=0 (disabled)
1784 kmemcheck=1 (enabled)
1785 kmemcheck=2 (one-shot mode)
1786 Default: 2 (one-shot mode)
1787
1788 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1789 Default is 0 (don't ignore, but inject #GP)
1790
1791 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1792 KVM MMU at runtime.
1793 Default is 0 (off)
1794
1795 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1796 Default is 1 (enabled)
1797
1798 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1799 for all guests.
1800 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1801
1802 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1803 (virtualized MMU) support on capable Intel chips.
1804 Default is 1 (enabled)
1805
1806 kvm-intel.emulate_invalid_guest_state=
1807 [KVM,Intel] Enable emulation of invalid guest states
1808 Default is 0 (disabled)
1809
1810 kvm-intel.flexpriority=
1811 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1812 Default is 1 (enabled)
1813
1814 kvm-intel.nested=
1815 [KVM,Intel] Enable VMX nesting (nVMX).
1816 Default is 0 (disabled)
1817
1818 kvm-intel.unrestricted_guest=
1819 [KVM,Intel] Disable unrestricted guest feature
1820 (virtualized real and unpaged mode) on capable
1821 Intel chips. Default is 1 (enabled)
1822
1823 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1824 feature (tagged TLBs) on capable Intel chips.
1825 Default is 1 (enabled)
1826
1827 l2cr= [PPC]
1828
1829 l3cr= [PPC]
1830
1831 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1832 disabled it.
1833
1834 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1835 value for LAPIC timer one-shot implementation. Default
1836 back to the programmable timer unit in the LAPIC.
1837
1838 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1839 in C2 power state.
1840
1841 libata.dma= [LIBATA] DMA control
1842 libata.dma=0 Disable all PATA and SATA DMA
1843 libata.dma=1 PATA and SATA Disk DMA only
1844 libata.dma=2 ATAPI (CDROM) DMA only
1845 libata.dma=4 Compact Flash DMA only
1846 Combinations also work, so libata.dma=3 enables DMA
1847 for disks and CDROMs, but not CFs.
1848
1849 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1850 libata.ignore_hpa=0 keep BIOS limits (default)
1851 libata.ignore_hpa=1 ignore limits, using full disk
1852
1853 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1854 when set.
1855 Format: <int>
1856
1857 libata.force= [LIBATA] Force configurations. The format is comma
1858 separated list of "[ID:]VAL" where ID is
1859 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1860 matching port, link or device. Basically, it matches
1861 the ATA ID string printed on console by libata. If
1862 the whole ID part is omitted, the last PORT and DEVICE
1863 values are used. If ID hasn't been specified yet, the
1864 configuration applies to all ports, links and devices.
1865
1866 If only DEVICE is omitted, the parameter applies to
1867 the port and all links and devices behind it. DEVICE
1868 number of 0 either selects the first device or the
1869 first fan-out link behind PMP device. It does not
1870 select the host link. DEVICE number of 15 selects the
1871 host link and device attached to it.
1872
1873 The VAL specifies the configuration to force. As long
1874 as there's no ambiguity shortcut notation is allowed.
1875 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1876 The following configurations can be forced.
1877
1878 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1879 Any ID with matching PORT is used.
1880
1881 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1882
1883 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1884 udma[/][16,25,33,44,66,100,133] notation is also
1885 allowed.
1886
1887 * [no]ncq: Turn on or off NCQ.
1888
1889 * [no]ncqtrim: Turn off queued DSM TRIM.
1890
1891 * nohrst, nosrst, norst: suppress hard, soft
1892 and both resets.
1893
1894 * rstonce: only attempt one reset during
1895 hot-unplug link recovery
1896
1897 * dump_id: dump IDENTIFY data.
1898
1899 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1900
1901 * disable: Disable this device.
1902
1903 If there are multiple matching configurations changing
1904 the same attribute, the last one is used.
1905
1906 memblock=debug [KNL] Enable memblock debug messages.
1907
1908 load_ramdisk= [RAM] List of ramdisks to load from floppy
1909 See Documentation/blockdev/ramdisk.txt.
1910
1911 lockd.nlm_grace_period=P [NFS] Assign grace period.
1912 Format: <integer>
1913
1914 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1915 Format: <integer>
1916
1917 lockd.nlm_timeout=T [NFS] Assign timeout value.
1918 Format: <integer>
1919
1920 lockd.nlm_udpport=M [NFS] Assign UDP port.
1921 Format: <integer>
1922
1923 locktorture.nreaders_stress= [KNL]
1924 Set the number of locking read-acquisition kthreads.
1925 Defaults to being automatically set based on the
1926 number of online CPUs.
1927
1928 locktorture.nwriters_stress= [KNL]
1929 Set the number of locking write-acquisition kthreads.
1930
1931 locktorture.onoff_holdoff= [KNL]
1932 Set time (s) after boot for CPU-hotplug testing.
1933
1934 locktorture.onoff_interval= [KNL]
1935 Set time (s) between CPU-hotplug operations, or
1936 zero to disable CPU-hotplug testing.
1937
1938 locktorture.shuffle_interval= [KNL]
1939 Set task-shuffle interval (jiffies). Shuffling
1940 tasks allows some CPUs to go into dyntick-idle
1941 mode during the locktorture test.
1942
1943 locktorture.shutdown_secs= [KNL]
1944 Set time (s) after boot system shutdown. This
1945 is useful for hands-off automated testing.
1946
1947 locktorture.stat_interval= [KNL]
1948 Time (s) between statistics printk()s.
1949
1950 locktorture.stutter= [KNL]
1951 Time (s) to stutter testing, for example,
1952 specifying five seconds causes the test to run for
1953 five seconds, wait for five seconds, and so on.
1954 This tests the locking primitive's ability to
1955 transition abruptly to and from idle.
1956
1957 locktorture.torture_runnable= [BOOT]
1958 Start locktorture running at boot time.
1959
1960 locktorture.torture_type= [KNL]
1961 Specify the locking implementation to test.
1962
1963 locktorture.verbose= [KNL]
1964 Enable additional printk() statements.
1965
1966 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1967 Format: <irq>
1968
1969 loglevel= All Kernel Messages with a loglevel smaller than the
1970 console loglevel will be printed to the console. It can
1971 also be changed with klogd or other programs. The
1972 loglevels are defined as follows:
1973
1974 0 (KERN_EMERG) system is unusable
1975 1 (KERN_ALERT) action must be taken immediately
1976 2 (KERN_CRIT) critical conditions
1977 3 (KERN_ERR) error conditions
1978 4 (KERN_WARNING) warning conditions
1979 5 (KERN_NOTICE) normal but significant condition
1980 6 (KERN_INFO) informational
1981 7 (KERN_DEBUG) debug-level messages
1982
1983 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1984 in bytes. n must be a power of two and greater
1985 than the minimal size. The minimal size is defined
1986 by LOG_BUF_SHIFT kernel config parameter. There is
1987 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1988 that allows to increase the default size depending on
1989 the number of CPUs. See init/Kconfig for more details.
1990
1991 logo.nologo [FB] Disables display of the built-in Linux logo.
1992 This may be used to provide more screen space for
1993 kernel log messages and is useful when debugging
1994 kernel boot problems.
1995
1996 lp=0 [LP] Specify parallel ports to use, e.g,
1997 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1998 lp=reset first parallel port). 'lp=0' disables the
1999 lp=auto printer driver. 'lp=reset' (which can be
2000 specified in addition to the ports) causes
2001 attached printers to be reset. Using
2002 lp=port1,port2,... specifies the parallel ports
2003 to associate lp devices with, starting with
2004 lp0. A port specification may be 'none' to skip
2005 that lp device, or a parport name such as
2006 'parport0'. Specifying 'lp=auto' instead of a
2007 port specification list means that device IDs
2008 from each port should be examined, to see if
2009 an IEEE 1284-compliant printer is attached; if
2010 so, the driver will manage that printer.
2011 See also header of drivers/char/lp.c.
2012
2013 lpj=n [KNL]
2014 Sets loops_per_jiffy to given constant, thus avoiding
2015 time-consuming boot-time autodetection (up to 250 ms per
2016 CPU). 0 enables autodetection (default). To determine
2017 the correct value for your kernel, boot with normal
2018 autodetection and see what value is printed. Note that
2019 on SMP systems the preset will be applied to all CPUs,
2020 which is likely to cause problems if your CPUs need
2021 significantly divergent settings. An incorrect value
2022 will cause delays in the kernel to be wrong, leading to
2023 unpredictable I/O errors and other breakage. Although
2024 unlikely, in the extreme case this might damage your
2025 hardware.
2026
2027 ltpc= [NET]
2028 Format: <io>,<irq>,<dma>
2029
2030 machvec= [IA-64] Force the use of a particular machine-vector
2031 (machvec) in a generic kernel.
2032 Example: machvec=hpzx1_swiotlb
2033
2034 machtype= [Loongson] Share the same kernel image file between different
2035 yeeloong laptop.
2036 Example: machtype=lemote-yeeloong-2f-7inch
2037
2038 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2039 than or equal to this physical address is ignored.
2040
2041 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2042 will bring up during bootup. maxcpus=n : n >= 0 limits
2043 the kernel to bring up 'n' processors. Surely after
2044 bootup you can bring up the other plugged cpu by executing
2045 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2046 only takes effect during system bootup.
2047 While n=0 is a special case, it is equivalent to "nosmp",
2048 which also disables the IO APIC.
2049
2050 max_loop= [LOOP] The number of loop block devices that get
2051 (loop.max_loop) unconditionally pre-created at init time. The default
2052 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2053 of statically allocating a predefined number, loop
2054 devices can be requested on-demand with the
2055 /dev/loop-control interface.
2056
2057 mce [X86-32] Machine Check Exception
2058
2059 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2060
2061 md= [HW] RAID subsystems devices and level
2062 See Documentation/admin-guide/md.rst.
2063
2064 mdacon= [MDA]
2065 Format: <first>,<last>
2066 Specifies range of consoles to be captured by the MDA.
2067
2068 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2069 Amount of memory to be used when the kernel is not able
2070 to see the whole system memory or for test.
2071 [X86] Work as limiting max address. Use together
2072 with memmap= to avoid physical address space collisions.
2073 Without memmap= PCI devices could be placed at addresses
2074 belonging to unused RAM.
2075
2076 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2077 memory.
2078
2079 memchunk=nn[KMG]
2080 [KNL,SH] Allow user to override the default size for
2081 per-device physically contiguous DMA buffers.
2082
2083 memhp_default_state=online/offline
2084 [KNL] Set the initial state for the memory hotplug
2085 onlining policy. If not specified, the default value is
2086 set according to the
2087 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2088 option.
2089 See Documentation/memory-hotplug.txt.
2090
2091 memmap=exactmap [KNL,X86] Enable setting of an exact
2092 E820 memory map, as specified by the user.
2093 Such memmap=exactmap lines can be constructed based on
2094 BIOS output or other requirements. See the memmap=nn@ss
2095 option description.
2096
2097 memmap=nn[KMG]@ss[KMG]
2098 [KNL] Force usage of a specific region of memory.
2099 Region of memory to be used is from ss to ss+nn.
2100
2101 memmap=nn[KMG]#ss[KMG]
2102 [KNL,ACPI] Mark specific memory as ACPI data.
2103 Region of memory to be marked is from ss to ss+nn.
2104
2105 memmap=nn[KMG]$ss[KMG]
2106 [KNL,ACPI] Mark specific memory as reserved.
2107 Region of memory to be reserved is from ss to ss+nn.
2108 Example: Exclude memory from 0x18690000-0x1869ffff
2109 memmap=64K$0x18690000
2110 or
2111 memmap=0x10000$0x18690000
2112
2113 memmap=nn[KMG]!ss[KMG]
2114 [KNL,X86] Mark specific memory as protected.
2115 Region of memory to be used, from ss to ss+nn.
2116 The memory region may be marked as e820 type 12 (0xc)
2117 and is NVDIMM or ADR memory.
2118
2119 memory_corruption_check=0/1 [X86]
2120 Some BIOSes seem to corrupt the first 64k of
2121 memory when doing things like suspend/resume.
2122 Setting this option will scan the memory
2123 looking for corruption. Enabling this will
2124 both detect corruption and prevent the kernel
2125 from using the memory being corrupted.
2126 However, its intended as a diagnostic tool; if
2127 repeatable BIOS-originated corruption always
2128 affects the same memory, you can use memmap=
2129 to prevent the kernel from using that memory.
2130
2131 memory_corruption_check_size=size [X86]
2132 By default it checks for corruption in the low
2133 64k, making this memory unavailable for normal
2134 use. Use this parameter to scan for
2135 corruption in more or less memory.
2136
2137 memory_corruption_check_period=seconds [X86]
2138 By default it checks for corruption every 60
2139 seconds. Use this parameter to check at some
2140 other rate. 0 disables periodic checking.
2141
2142 memtest= [KNL,X86,ARM] Enable memtest
2143 Format: <integer>
2144 default : 0 <disable>
2145 Specifies the number of memtest passes to be
2146 performed. Each pass selects another test
2147 pattern from a given set of patterns. Memtest
2148 fills the memory with this pattern, validates
2149 memory contents and reserves bad memory
2150 regions that are detected.
2151
2152 mem_sleep_default= [SUSPEND] Default system suspend mode:
2153 s2idle - Suspend-To-Idle
2154 shallow - Power-On Suspend or equivalent (if supported)
2155 deep - Suspend-To-RAM or equivalent (if supported)
2156 See Documentation/power/states.txt.
2157
2158 meye.*= [HW] Set MotionEye Camera parameters
2159 See Documentation/video4linux/meye.txt.
2160
2161 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2162 Multi-Function General Purpose Timers on AMD Geode
2163 platforms.
2164
2165 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2166 the BIOS has incorrectly applied a workaround. TinyBIOS
2167 version 0.98 is known to be affected, 0.99 fixes the
2168 problem by letting the user disable the workaround.
2169
2170 mga= [HW,DRM]
2171
2172 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2173 physical address is ignored.
2174
2175 mini2440= [ARM,HW,KNL]
2176 Format:[0..2][b][c][t]
2177 Default: "0tb"
2178 MINI2440 configuration specification:
2179 0 - The attached screen is the 3.5" TFT
2180 1 - The attached screen is the 7" TFT
2181 2 - The VGA Shield is attached (1024x768)
2182 Leaving out the screen size parameter will not load
2183 the TFT driver, and the framebuffer will be left
2184 unconfigured.
2185 b - Enable backlight. The TFT backlight pin will be
2186 linked to the kernel VESA blanking code and a GPIO
2187 LED. This parameter is not necessary when using the
2188 VGA shield.
2189 c - Enable the s3c camera interface.
2190 t - Reserved for enabling touchscreen support. The
2191 touchscreen support is not enabled in the mainstream
2192 kernel as of 2.6.30, a preliminary port can be found
2193 in the "bleeding edge" mini2440 support kernel at
2194 http://repo.or.cz/w/linux-2.6/mini2440.git
2195
2196 mminit_loglevel=
2197 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2198 parameter allows control of the logging verbosity for
2199 the additional memory initialisation checks. A value
2200 of 0 disables mminit logging and a level of 4 will
2201 log everything. Information is printed at KERN_DEBUG
2202 so loglevel=8 may also need to be specified.
2203
2204 module.sig_enforce
2205 [KNL] When CONFIG_MODULE_SIG is set, this means that
2206 modules without (valid) signatures will fail to load.
2207 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2208 is always true, so this option does nothing.
2209
2210 module_blacklist= [KNL] Do not load a comma-separated list of
2211 modules. Useful for debugging problem modules.
2212
2213 mousedev.tap_time=
2214 [MOUSE] Maximum time between finger touching and
2215 leaving touchpad surface for touch to be considered
2216 a tap and be reported as a left button click (for
2217 touchpads working in absolute mode only).
2218 Format: <msecs>
2219 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2220 reporting absolute coordinates, such as tablets
2221 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2222 reporting absolute coordinates, such as tablets
2223
2224 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2225 is similar to kernelcore except it specifies the
2226 amount of memory used for migratable allocations.
2227 If both kernelcore and movablecore is specified,
2228 then kernelcore will be at *least* the specified
2229 value but may be more. If movablecore on its own
2230 is specified, the administrator must be careful
2231 that the amount of memory usable for all allocations
2232 is not too small.
2233
2234 movable_node [KNL] Boot-time switch to enable the effects
2235 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2236
2237 MTD_Partition= [MTD]
2238 Format: <name>,<region-number>,<size>,<offset>
2239
2240 MTD_Region= [MTD] Format:
2241 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2242
2243 mtdparts= [MTD]
2244 See drivers/mtd/cmdlinepart.c.
2245
2246 multitce=off [PPC] This parameter disables the use of the pSeries
2247 firmware feature for updating multiple TCE entries
2248 at a time.
2249
2250 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2251
2252 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2253
2254 boundary - index of last SLC block on Flex-OneNAND.
2255 The remaining blocks are configured as MLC blocks.
2256 lock - Configure if Flex-OneNAND boundary should be locked.
2257 Once locked, the boundary cannot be changed.
2258 1 indicates lock status, 0 indicates unlock status.
2259
2260 mtdset= [ARM]
2261 ARM/S3C2412 JIVE boot control
2262
2263 See arch/arm/mach-s3c2412/mach-jive.c
2264
2265 mtouchusb.raw_coordinates=
2266 [HW] Make the MicroTouch USB driver use raw coordinates
2267 ('y', default) or cooked coordinates ('n')
2268
2269 mtrr_chunk_size=nn[KMG] [X86]
2270 used for mtrr cleanup. It is largest continuous chunk
2271 that could hold holes aka. UC entries.
2272
2273 mtrr_gran_size=nn[KMG] [X86]
2274 Used for mtrr cleanup. It is granularity of mtrr block.
2275 Default is 1.
2276 Large value could prevent small alignment from
2277 using up MTRRs.
2278
2279 mtrr_spare_reg_nr=n [X86]
2280 Format: <integer>
2281 Range: 0,7 : spare reg number
2282 Default : 1
2283 Used for mtrr cleanup. It is spare mtrr entries number.
2284 Set to 2 or more if your graphical card needs more.
2285
2286 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2287
2288 netdev= [NET] Network devices parameters
2289 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2290 Note that mem_start is often overloaded to mean
2291 something different and driver-specific.
2292 This usage is only documented in each driver source
2293 file if at all.
2294
2295 nf_conntrack.acct=
2296 [NETFILTER] Enable connection tracking flow accounting
2297 0 to disable accounting
2298 1 to enable accounting
2299 Default value is 0.
2300
2301 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2302 See Documentation/filesystems/nfs/nfsroot.txt.
2303
2304 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2305 See Documentation/filesystems/nfs/nfsroot.txt.
2306
2307 nfsrootdebug [NFS] enable nfsroot debugging messages.
2308 See Documentation/filesystems/nfs/nfsroot.txt.
2309
2310 nfs.callback_nr_threads=
2311 [NFSv4] set the total number of threads that the
2312 NFS client will assign to service NFSv4 callback
2313 requests.
2314
2315 nfs.callback_tcpport=
2316 [NFS] set the TCP port on which the NFSv4 callback
2317 channel should listen.
2318
2319 nfs.cache_getent=
2320 [NFS] sets the pathname to the program which is used
2321 to update the NFS client cache entries.
2322
2323 nfs.cache_getent_timeout=
2324 [NFS] sets the timeout after which an attempt to
2325 update a cache entry is deemed to have failed.
2326
2327 nfs.idmap_cache_timeout=
2328 [NFS] set the maximum lifetime for idmapper cache
2329 entries.
2330
2331 nfs.enable_ino64=
2332 [NFS] enable 64-bit inode numbers.
2333 If zero, the NFS client will fake up a 32-bit inode
2334 number for the readdir() and stat() syscalls instead
2335 of returning the full 64-bit number.
2336 The default is to return 64-bit inode numbers.
2337
2338 nfs.max_session_cb_slots=
2339 [NFSv4.1] Sets the maximum number of session
2340 slots the client will assign to the callback
2341 channel. This determines the maximum number of
2342 callbacks the client will process in parallel for
2343 a particular server.
2344
2345 nfs.max_session_slots=
2346 [NFSv4.1] Sets the maximum number of session slots
2347 the client will attempt to negotiate with the server.
2348 This limits the number of simultaneous RPC requests
2349 that the client can send to the NFSv4.1 server.
2350 Note that there is little point in setting this
2351 value higher than the max_tcp_slot_table_limit.
2352
2353 nfs.nfs4_disable_idmapping=
2354 [NFSv4] When set to the default of '1', this option
2355 ensures that both the RPC level authentication
2356 scheme and the NFS level operations agree to use
2357 numeric uids/gids if the mount is using the
2358 'sec=sys' security flavour. In effect it is
2359 disabling idmapping, which can make migration from
2360 legacy NFSv2/v3 systems to NFSv4 easier.
2361 Servers that do not support this mode of operation
2362 will be autodetected by the client, and it will fall
2363 back to using the idmapper.
2364 To turn off this behaviour, set the value to '0'.
2365 nfs.nfs4_unique_id=
2366 [NFS4] Specify an additional fixed unique ident-
2367 ification string that NFSv4 clients can insert into
2368 their nfs_client_id4 string. This is typically a
2369 UUID that is generated at system install time.
2370
2371 nfs.send_implementation_id =
2372 [NFSv4.1] Send client implementation identification
2373 information in exchange_id requests.
2374 If zero, no implementation identification information
2375 will be sent.
2376 The default is to send the implementation identification
2377 information.
2378
2379 nfs.recover_lost_locks =
2380 [NFSv4] Attempt to recover locks that were lost due
2381 to a lease timeout on the server. Please note that
2382 doing this risks data corruption, since there are
2383 no guarantees that the file will remain unchanged
2384 after the locks are lost.
2385 If you want to enable the kernel legacy behaviour of
2386 attempting to recover these locks, then set this
2387 parameter to '1'.
2388 The default parameter value of '0' causes the kernel
2389 not to attempt recovery of lost locks.
2390
2391 nfs4.layoutstats_timer =
2392 [NFSv4.2] Change the rate at which the kernel sends
2393 layoutstats to the pNFS metadata server.
2394
2395 Setting this to value to 0 causes the kernel to use
2396 whatever value is the default set by the layout
2397 driver. A non-zero value sets the minimum interval
2398 in seconds between layoutstats transmissions.
2399
2400 nfsd.nfs4_disable_idmapping=
2401 [NFSv4] When set to the default of '1', the NFSv4
2402 server will return only numeric uids and gids to
2403 clients using auth_sys, and will accept numeric uids
2404 and gids from such clients. This is intended to ease
2405 migration from NFSv2/v3.
2406
2407 objlayoutdriver.osd_login_prog=
2408 [NFS] [OBJLAYOUT] sets the pathname to the program which
2409 is used to automatically discover and login into new
2410 osd-targets. Please see:
2411 Documentation/filesystems/pnfs.txt for more explanations
2412
2413 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2414 when a NMI is triggered.
2415 Format: [state][,regs][,debounce][,die]
2416
2417 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2418 Format: [panic,][nopanic,][num]
2419 Valid num: 0 or 1
2420 0 - turn hardlockup detector in nmi_watchdog off
2421 1 - turn hardlockup detector in nmi_watchdog on
2422 When panic is specified, panic when an NMI watchdog
2423 timeout occurs (or 'nopanic' to override the opposite
2424 default). To disable both hard and soft lockup detectors,
2425 please see 'nowatchdog'.
2426 This is useful when you use a panic=... timeout and
2427 need the box quickly up again.
2428
2429 netpoll.carrier_timeout=
2430 [NET] Specifies amount of time (in seconds) that
2431 netpoll should wait for a carrier. By default netpoll
2432 waits 4 seconds.
2433
2434 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2435 emulation library even if a 387 maths coprocessor
2436 is present.
2437
2438 no_console_suspend
2439 [HW] Never suspend the console
2440 Disable suspending of consoles during suspend and
2441 hibernate operations. Once disabled, debugging
2442 messages can reach various consoles while the rest
2443 of the system is being put to sleep (ie, while
2444 debugging driver suspend/resume hooks). This may
2445 not work reliably with all consoles, but is known
2446 to work with serial and VGA consoles.
2447 To facilitate more flexible debugging, we also add
2448 console_suspend, a printk module parameter to control
2449 it. Users could use console_suspend (usually
2450 /sys/module/printk/parameters/console_suspend) to
2451 turn on/off it dynamically.
2452
2453 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2454 caches in the slab allocator. Saves per-node memory,
2455 but will impact performance.
2456
2457 noalign [KNL,ARM]
2458
2459 noapic [SMP,APIC] Tells the kernel to not make use of any
2460 IOAPICs that may be present in the system.
2461
2462 noautogroup Disable scheduler automatic task group creation.
2463
2464 nobats [PPC] Do not use BATs for mapping kernel lowmem
2465 on "Classic" PPC cores.
2466
2467 nocache [ARM]
2468
2469 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2470
2471 nodelayacct [KNL] Disable per-task delay accounting
2472
2473 nodsp [SH] Disable hardware DSP at boot time.
2474
2475 noefi Disable EFI runtime services support.
2476
2477 noexec [IA-64]
2478
2479 noexec [X86]
2480 On X86-32 available only on PAE configured kernels.
2481 noexec=on: enable non-executable mappings (default)
2482 noexec=off: disable non-executable mappings
2483
2484 nosmap [X86]
2485 Disable SMAP (Supervisor Mode Access Prevention)
2486 even if it is supported by processor.
2487
2488 nosmep [X86]
2489 Disable SMEP (Supervisor Mode Execution Prevention)
2490 even if it is supported by processor.
2491
2492 noexec32 [X86-64]
2493 This affects only 32-bit executables.
2494 noexec32=on: enable non-executable mappings (default)
2495 read doesn't imply executable mappings
2496 noexec32=off: disable non-executable mappings
2497 read implies executable mappings
2498
2499 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2500
2501 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2502 register save and restore. The kernel will only save
2503 legacy floating-point registers on task switch.
2504
2505 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2506
2507 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
2508 Equivalent to smt=1.
2509
2510 noxsave [BUGS=X86] Disables x86 extended register state save
2511 and restore using xsave. The kernel will fallback to
2512 enabling legacy floating-point and sse state.
2513
2514 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2515 register states. The kernel will fall back to use
2516 xsave to save the states. By using this parameter,
2517 performance of saving the states is degraded because
2518 xsave doesn't support modified optimization while
2519 xsaveopt supports it on xsaveopt enabled systems.
2520
2521 noxsaves [X86] Disables xsaves and xrstors used in saving and
2522 restoring x86 extended register state in compacted
2523 form of xsave area. The kernel will fall back to use
2524 xsaveopt and xrstor to save and restore the states
2525 in standard form of xsave area. By using this
2526 parameter, xsave area per process might occupy more
2527 memory on xsaves enabled systems.
2528
2529 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2530 wfi(ARM) instruction doesn't work correctly and not to
2531 use it. This is also useful when using JTAG debugger.
2532
2533 no_file_caps Tells the kernel not to honor file capabilities. The
2534 only way then for a file to be executed with privilege
2535 is to be setuid root or executed by root.
2536
2537 nohalt [IA-64] Tells the kernel not to use the power saving
2538 function PAL_HALT_LIGHT when idle. This increases
2539 power-consumption. On the positive side, it reduces
2540 interrupt wake-up latency, which may improve performance
2541 in certain environments such as networked servers or
2542 real-time systems.
2543
2544 nohibernate [HIBERNATION] Disable hibernation and resume.
2545
2546 nohz= [KNL] Boottime enable/disable dynamic ticks
2547 Valid arguments: on, off
2548 Default: on
2549
2550 nohz_full= [KNL,BOOT]
2551 The argument is a cpu list, as described above.
2552 In kernels built with CONFIG_NO_HZ_FULL=y, set
2553 the specified list of CPUs whose tick will be stopped
2554 whenever possible. The boot CPU will be forced outside
2555 the range to maintain the timekeeping.
2556 The CPUs in this range must also be included in the
2557 rcu_nocbs= set.
2558
2559 noiotrap [SH] Disables trapped I/O port accesses.
2560
2561 noirqdebug [X86-32] Disables the code which attempts to detect and
2562 disable unhandled interrupt sources.
2563
2564 no_timer_check [X86,APIC] Disables the code which tests for
2565 broken timer IRQ sources.
2566
2567 noisapnp [ISAPNP] Disables ISA PnP code.
2568
2569 noinitrd [RAM] Tells the kernel not to load any configured
2570 initial RAM disk.
2571
2572 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2573 remapping.
2574 [Deprecated - use intremap=off]
2575
2576 nointroute [IA-64]
2577
2578 noinvpcid [X86] Disable the INVPCID cpu feature.
2579
2580 nojitter [IA-64] Disables jitter checking for ITC timers.
2581
2582 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2583
2584 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2585 fault handling.
2586
2587 no-vmw-sched-clock
2588 [X86,PV_OPS] Disable paravirtualized VMware scheduler
2589 clock and use the default one.
2590
2591 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2592 steal time is computed, but won't influence scheduler
2593 behaviour
2594
2595 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2596
2597 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2598
2599 noltlbs [PPC] Do not use large page/tlb entries for kernel
2600 lowmem mapping on PPC40x and PPC8xx
2601
2602 nomca [IA-64] Disable machine check abort handling
2603
2604 nomce [X86-32] Disable Machine Check Exception
2605
2606 nomfgpt [X86-32] Disable Multi-Function General Purpose
2607 Timer usage (for AMD Geode machines).
2608
2609 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2610 shutdown the other cpus. Instead use the REBOOT_VECTOR
2611 irq.
2612
2613 nomodule Disable module load
2614
2615 nopat [X86] Disable PAT (page attribute table extension of
2616 pagetables) support.
2617
2618 norandmaps Don't use address space randomization. Equivalent to
2619 echo 0 > /proc/sys/kernel/randomize_va_space
2620
2621 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2622
2623 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2624 with UP alternatives
2625
2626 nordrand [X86] Disable kernel use of the RDRAND and
2627 RDSEED instructions even if they are supported
2628 by the processor. RDRAND and RDSEED are still
2629 available to user space applications.
2630
2631 noresume [SWSUSP] Disables resume and restores original swap
2632 space.
2633
2634 no-scroll [VGA] Disables scrollback.
2635 This is required for the Braillex ib80-piezo Braille
2636 reader made by F.H. Papenmeier (Germany).
2637
2638 nosbagart [IA-64]
2639
2640 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2641
2642 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2643 and disable the IO APIC. legacy for "maxcpus=0".
2644
2645 nosoftlockup [KNL] Disable the soft-lockup detector.
2646
2647 nosync [HW,M68K] Disables sync negotiation for all devices.
2648
2649 notsc [BUGS=X86-32] Disable Time Stamp Counter
2650
2651 nowatchdog [KNL] Disable both lockup detectors, i.e.
2652 soft-lockup and NMI watchdog (hard-lockup).
2653
2654 nowb [ARM]
2655
2656 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2657
2658 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2659 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2660 Some features depend on CPU0. Known dependencies are:
2661 1. Resume from suspend/hibernate depends on CPU0.
2662 Suspend/hibernate will fail if CPU0 is offline and you
2663 need to online CPU0 before suspend/hibernate.
2664 2. PIC interrupts also depend on CPU0. CPU0 can't be
2665 removed if a PIC interrupt is detected.
2666 It's said poweroff/reboot may depend on CPU0 on some
2667 machines although I haven't seen such issues so far
2668 after CPU0 is offline on a few tested machines.
2669 If the dependencies are under your control, you can
2670 turn on cpu0_hotplug.
2671
2672 nptcg= [IA-64] Override max number of concurrent global TLB
2673 purges which is reported from either PAL_VM_SUMMARY or
2674 SAL PALO.
2675
2676 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2677 could support. nr_cpus=n : n >= 1 limits the kernel to
2678 support 'n' processors. It could be larger than the
2679 number of already plugged CPU during bootup, later in
2680 runtime you can physically add extra cpu until it reaches
2681 n. So during boot up some boot time memory for per-cpu
2682 variables need be pre-allocated for later physical cpu
2683 hot plugging.
2684
2685 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2686
2687 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2688 Allowed values are enable and disable
2689
2690 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2691 one of ['zone', 'node', 'default'] can be specified
2692 This can be set from sysctl after boot.
2693 See Documentation/sysctl/vm.txt for details.
2694
2695 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2696 See Documentation/debugging-via-ohci1394.txt for more
2697 info.
2698
2699 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2700 Rather than timing out after 20 ms if an EC
2701 command is not properly ACKed, override the length
2702 of the timeout. We have interrupts disabled while
2703 waiting for the ACK, so if this is set too high
2704 interrupts *may* be lost!
2705
2706 omap_mux= [OMAP] Override bootloader pin multiplexing.
2707 Format: <mux_mode0.mode_name=value>...
2708 For example, to override I2C bus2:
2709 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2710
2711 oprofile.timer= [HW]
2712 Use timer interrupt instead of performance counters
2713
2714 oprofile.cpu_type= Force an oprofile cpu type
2715 This might be useful if you have an older oprofile
2716 userland or if you want common events.
2717 Format: { arch_perfmon }
2718 arch_perfmon: [X86] Force use of architectural
2719 perfmon on Intel CPUs instead of the
2720 CPU specific event set.
2721 timer: [X86] Force use of architectural NMI
2722 timer mode (see also oprofile.timer
2723 for generic hr timer mode)
2724
2725 oops=panic Always panic on oopses. Default is to just kill the
2726 process, but there is a small probability of
2727 deadlocking the machine.
2728 This will also cause panics on machine check exceptions.
2729 Useful together with panic=30 to trigger a reboot.
2730
2731 OSS [HW,OSS]
2732 See Documentation/sound/oss/oss-parameters.txt
2733
2734 page_owner= [KNL] Boot-time page_owner enabling option.
2735 Storage of the information about who allocated
2736 each page is disabled in default. With this switch,
2737 we can turn it on.
2738 on: enable the feature
2739
2740 page_poison= [KNL] Boot-time parameter changing the state of
2741 poisoning on the buddy allocator.
2742 off: turn off poisoning
2743 on: turn on poisoning
2744
2745 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2746 timeout > 0: seconds before rebooting
2747 timeout = 0: wait forever
2748 timeout < 0: reboot immediately
2749 Format: <timeout>
2750
2751 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2752 on a WARN().
2753
2754 crash_kexec_post_notifiers
2755 Run kdump after running panic-notifiers and dumping
2756 kmsg. This only for the users who doubt kdump always
2757 succeeds in any situation.
2758 Note that this also increases risks of kdump failure,
2759 because some panic notifiers can make the crashed
2760 kernel more unstable.
2761
2762 parkbd.port= [HW] Parallel port number the keyboard adapter is
2763 connected to, default is 0.
2764 Format: <parport#>
2765 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2766 0 for XT, 1 for AT (default is AT).
2767 Format: <mode>
2768
2769 parport= [HW,PPT] Specify parallel ports. 0 disables.
2770 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2771 Use 'auto' to force the driver to use any
2772 IRQ/DMA settings detected (the default is to
2773 ignore detected IRQ/DMA settings because of
2774 possible conflicts). You can specify the base
2775 address, IRQ, and DMA settings; IRQ and DMA
2776 should be numbers, or 'auto' (for using detected
2777 settings on that particular port), or 'nofifo'
2778 (to avoid using a FIFO even if it is detected).
2779 Parallel ports are assigned in the order they
2780 are specified on the command line, starting
2781 with parport0.
2782
2783 parport_init_mode= [HW,PPT]
2784 Configure VIA parallel port to operate in
2785 a specific mode. This is necessary on Pegasos
2786 computer where firmware has no options for setting
2787 up parallel port mode and sets it to spp.
2788 Currently this function knows 686a and 8231 chips.
2789 Format: [spp|ps2|epp|ecp|ecpepp]
2790
2791 pause_on_oops=
2792 Halt all CPUs after the first oops has been printed for
2793 the specified number of seconds. This is to be used if
2794 your oopses keep scrolling off the screen.
2795
2796 pcbit= [HW,ISDN]
2797
2798 pcd. [PARIDE]
2799 See header of drivers/block/paride/pcd.c.
2800 See also Documentation/blockdev/paride.txt.
2801
2802 pci=option[,option...] [PCI] various PCI subsystem options:
2803 earlydump [X86] dump PCI config space before the kernel
2804 changes anything
2805 off [X86] don't probe for the PCI bus
2806 bios [X86-32] force use of PCI BIOS, don't access
2807 the hardware directly. Use this if your machine
2808 has a non-standard PCI host bridge.
2809 nobios [X86-32] disallow use of PCI BIOS, only direct
2810 hardware access methods are allowed. Use this
2811 if you experience crashes upon bootup and you
2812 suspect they are caused by the BIOS.
2813 conf1 [X86] Force use of PCI Configuration Access
2814 Mechanism 1 (config address in IO port 0xCF8,
2815 data in IO port 0xCFC, both 32-bit).
2816 conf2 [X86] Force use of PCI Configuration Access
2817 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2818 the function, IO port 0xCFA, also 8-bit, sets
2819 bus number. The config space is then accessed
2820 through ports 0xC000-0xCFFF).
2821 See http://wiki.osdev.org/PCI for more info
2822 on the configuration access mechanisms.
2823 noaer [PCIE] If the PCIEAER kernel config parameter is
2824 enabled, this kernel boot option can be used to
2825 disable the use of PCIE advanced error reporting.
2826 nodomains [PCI] Disable support for multiple PCI
2827 root domains (aka PCI segments, in ACPI-speak).
2828 nommconf [X86] Disable use of MMCONFIG for PCI
2829 Configuration
2830 check_enable_amd_mmconf [X86] check for and enable
2831 properly configured MMIO access to PCI
2832 config space on AMD family 10h CPU
2833 nomsi [MSI] If the PCI_MSI kernel config parameter is
2834 enabled, this kernel boot option can be used to
2835 disable the use of MSI interrupts system-wide.
2836 noioapicquirk [APIC] Disable all boot interrupt quirks.
2837 Safety option to keep boot IRQs enabled. This
2838 should never be necessary.
2839 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2840 primary IO-APIC for bridges that cannot disable
2841 boot IRQs. This fixes a source of spurious IRQs
2842 when the system masks IRQs.
2843 noioapicreroute [APIC] Disable workaround that uses the
2844 boot IRQ equivalent of an IRQ that connects to
2845 a chipset where boot IRQs cannot be disabled.
2846 The opposite of ioapicreroute.
2847 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2848 routing table. These calls are known to be buggy
2849 on several machines and they hang the machine
2850 when used, but on other computers it's the only
2851 way to get the interrupt routing table. Try
2852 this option if the kernel is unable to allocate
2853 IRQs or discover secondary PCI buses on your
2854 motherboard.
2855 rom [X86] Assign address space to expansion ROMs.
2856 Use with caution as certain devices share
2857 address decoders between ROMs and other
2858 resources.
2859 norom [X86] Do not assign address space to
2860 expansion ROMs that do not already have
2861 BIOS assigned address ranges.
2862 nobar [X86] Do not assign address space to the
2863 BARs that weren't assigned by the BIOS.
2864 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2865 assigned automatically to PCI devices. You can
2866 make the kernel exclude IRQs of your ISA cards
2867 this way.
2868 pirqaddr=0xAAAAA [X86] Specify the physical address
2869 of the PIRQ table (normally generated
2870 by the BIOS) if it is outside the
2871 F0000h-100000h range.
2872 lastbus=N [X86] Scan all buses thru bus #N. Can be
2873 useful if the kernel is unable to find your
2874 secondary buses and you want to tell it
2875 explicitly which ones they are.
2876 assign-busses [X86] Always assign all PCI bus
2877 numbers ourselves, overriding
2878 whatever the firmware may have done.
2879 usepirqmask [X86] Honor the possible IRQ mask stored
2880 in the BIOS $PIR table. This is needed on
2881 some systems with broken BIOSes, notably
2882 some HP Pavilion N5400 and Omnibook XE3
2883 notebooks. This will have no effect if ACPI
2884 IRQ routing is enabled.
2885 noacpi [X86] Do not use ACPI for IRQ routing
2886 or for PCI scanning.
2887 use_crs [X86] Use PCI host bridge window information
2888 from ACPI. On BIOSes from 2008 or later, this
2889 is enabled by default. If you need to use this,
2890 please report a bug.
2891 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2892 If you need to use this, please report a bug.
2893 routeirq Do IRQ routing for all PCI devices.
2894 This is normally done in pci_enable_device(),
2895 so this option is a temporary workaround
2896 for broken drivers that don't call it.
2897 skip_isa_align [X86] do not align io start addr, so can
2898 handle more pci cards
2899 noearly [X86] Don't do any early type 1 scanning.
2900 This might help on some broken boards which
2901 machine check when some devices' config space
2902 is read. But various workarounds are disabled
2903 and some IOMMU drivers will not work.
2904 bfsort Sort PCI devices into breadth-first order.
2905 This sorting is done to get a device
2906 order compatible with older (<= 2.4) kernels.
2907 nobfsort Don't sort PCI devices into breadth-first order.
2908 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2909 tuning and use the BIOS-configured MPS defaults.
2910 pcie_bus_safe Set every device's MPS to the largest value
2911 supported by all devices below the root complex.
2912 pcie_bus_perf Set device MPS to the largest allowable MPS
2913 based on its parent bus. Also set MRRS (Max
2914 Read Request Size) to the largest supported
2915 value (no larger than the MPS that the device
2916 or bus can support) for best performance.
2917 pcie_bus_peer2peer Set every device's MPS to 128B, which
2918 every device is guaranteed to support. This
2919 configuration allows peer-to-peer DMA between
2920 any pair of devices, possibly at the cost of
2921 reduced performance. This also guarantees
2922 that hot-added devices will work.
2923 cbiosize=nn[KMG] The fixed amount of bus space which is
2924 reserved for the CardBus bridge's IO window.
2925 The default value is 256 bytes.
2926 cbmemsize=nn[KMG] The fixed amount of bus space which is
2927 reserved for the CardBus bridge's memory
2928 window. The default value is 64 megabytes.
2929 resource_alignment=
2930 Format:
2931 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2932 [<order of align>@]pci:<vendor>:<device>\
2933 [:<subvendor>:<subdevice>][; ...]
2934 Specifies alignment and device to reassign
2935 aligned memory resources.
2936 If <order of align> is not specified,
2937 PAGE_SIZE is used as alignment.
2938 PCI-PCI bridge can be specified, if resource
2939 windows need to be expanded.
2940 To specify the alignment for several
2941 instances of a device, the PCI vendor,
2942 device, subvendor, and subdevice may be
2943 specified, e.g., 4096@pci:8086:9c22:103c:198f
2944 ecrc= Enable/disable PCIe ECRC (transaction layer
2945 end-to-end CRC checking).
2946 bios: Use BIOS/firmware settings. This is the
2947 the default.
2948 off: Turn ECRC off
2949 on: Turn ECRC on.
2950 hpiosize=nn[KMG] The fixed amount of bus space which is
2951 reserved for hotplug bridge's IO window.
2952 Default size is 256 bytes.
2953 hpmemsize=nn[KMG] The fixed amount of bus space which is
2954 reserved for hotplug bridge's memory window.
2955 Default size is 2 megabytes.
2956 hpbussize=nn The minimum amount of additional bus numbers
2957 reserved for buses below a hotplug bridge.
2958 Default is 1.
2959 realloc= Enable/disable reallocating PCI bridge resources
2960 if allocations done by BIOS are too small to
2961 accommodate resources required by all child
2962 devices.
2963 off: Turn realloc off
2964 on: Turn realloc on
2965 realloc same as realloc=on
2966 noari do not use PCIe ARI.
2967 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2968 only look for one device below a PCIe downstream
2969 port.
2970
2971 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2972 Management.
2973 off Disable ASPM.
2974 force Enable ASPM even on devices that claim not to support it.
2975 WARNING: Forcing ASPM on may cause system lockups.
2976
2977 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2978 nomsi Do not use MSI for PCI Express Native Hotplug (this
2979 makes all PCIe ports use INTx for hotplug services).
2980
2981 pcie_ports= [PCIE] PCIe ports handling:
2982 auto Ask the BIOS whether or not to use native PCIe services
2983 associated with PCIe ports (PME, hot-plug, AER). Use
2984 them only if that is allowed by the BIOS.
2985 native Use native PCIe services associated with PCIe ports
2986 unconditionally.
2987 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2988 ports driver.
2989
2990 pcie_port_pm= [PCIE] PCIe port power management handling:
2991 off Disable power management of all PCIe ports
2992 force Forcibly enable power management of all PCIe ports
2993
2994 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2995 nomsi Do not use MSI for native PCIe PME signaling (this makes
2996 all PCIe root ports use INTx for all services).
2997
2998 pcmv= [HW,PCMCIA] BadgePAD 4
2999
3000 pd_ignore_unused
3001 [PM]
3002 Keep all power-domains already enabled by bootloader on,
3003 even if no driver has claimed them. This is useful
3004 for debug and development, but should not be
3005 needed on a platform with proper driver support.
3006
3007 pd. [PARIDE]
3008 See Documentation/blockdev/paride.txt.
3009
3010 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
3011 boot time.
3012 Format: { 0 | 1 }
3013 See arch/parisc/kernel/pdc_chassis.c
3014
3015 percpu_alloc= Select which percpu first chunk allocator to use.
3016 Currently supported values are "embed" and "page".
3017 Archs may support subset or none of the selections.
3018 See comments in mm/percpu.c for details on each
3019 allocator. This parameter is primarily for debugging
3020 and performance comparison.
3021
3022 pf. [PARIDE]
3023 See Documentation/blockdev/paride.txt.
3024
3025 pg. [PARIDE]
3026 See Documentation/blockdev/paride.txt.
3027
3028 pirq= [SMP,APIC] Manual mp-table setup
3029 See Documentation/x86/i386/IO-APIC.txt.
3030
3031 plip= [PPT,NET] Parallel port network link
3032 Format: { parport<nr> | timid | 0 }
3033 See also Documentation/parport.txt.
3034
3035 pmtmr= [X86] Manual setup of pmtmr I/O Port.
3036 Override pmtimer IOPort with a hex value.
3037 e.g. pmtmr=0x508
3038
3039 pnp.debug=1 [PNP]
3040 Enable PNP debug messages (depends on the
3041 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
3042 via /sys/module/pnp/parameters/debug. We always show
3043 current resource usage; turning this on also shows
3044 possible settings and some assignment information.
3045
3046 pnpacpi= [ACPI]
3047 { off }
3048
3049 pnpbios= [ISAPNP]
3050 { on | off | curr | res | no-curr | no-res }
3051
3052 pnp_reserve_irq=
3053 [ISAPNP] Exclude IRQs for the autoconfiguration
3054
3055 pnp_reserve_dma=
3056 [ISAPNP] Exclude DMAs for the autoconfiguration
3057
3058 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
3059 Ranges are in pairs (I/O port base and size).
3060
3061 pnp_reserve_mem=
3062 [ISAPNP] Exclude memory regions for the
3063 autoconfiguration.
3064 Ranges are in pairs (memory base and size).
3065
3066 ports= [IP_VS_FTP] IPVS ftp helper module
3067 Default is 21.
3068 Up to 8 (IP_VS_APP_MAX_PORTS) ports
3069 may be specified.
3070 Format: <port>,<port>....
3071
3072 powersave=off [PPC] This option disables power saving features.
3073 It specifically disables cpuidle and sets the
3074 platform machine description specific power_save
3075 function to NULL. On Idle the CPU just reduces
3076 execution priority.
3077
3078 ppc_strict_facility_enable
3079 [PPC] This option catches any kernel floating point,
3080 Altivec, VSX and SPE outside of regions specifically
3081 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3082 There is some performance impact when enabling this.
3083
3084 print-fatal-signals=
3085 [KNL] debug: print fatal signals
3086
3087 If enabled, warn about various signal handling
3088 related application anomalies: too many signals,
3089 too many POSIX.1 timers, fatal signals causing a
3090 coredump - etc.
3091
3092 If you hit the warning due to signal overflow,
3093 you might want to try "ulimit -i unlimited".
3094
3095 default: off.
3096
3097 printk.always_kmsg_dump=
3098 Trigger kmsg_dump for cases other than kernel oops or
3099 panics
3100 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3101 default: disabled
3102
3103 printk.devkmsg={on,off,ratelimit}
3104 Control writing to /dev/kmsg.
3105 on - unlimited logging to /dev/kmsg from userspace
3106 off - logging to /dev/kmsg disabled
3107 ratelimit - ratelimit the logging
3108 Default: ratelimit
3109
3110 printk.time= Show timing data prefixed to each printk message line
3111 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3112
3113 processor.max_cstate= [HW,ACPI]
3114 Limit processor to maximum C-state
3115 max_cstate=9 overrides any DMI blacklist limit.
3116
3117 processor.nocst [HW,ACPI]
3118 Ignore the _CST method to determine C-states,
3119 instead using the legacy FADT method
3120
3121 profile= [KNL] Enable kernel profiling via /proc/profile
3122 Format: [schedule,]<number>
3123 Param: "schedule" - profile schedule points.
3124 Param: <number> - step/bucket size as a power of 2 for
3125 statistical time based profiling.
3126 Param: "sleep" - profile D-state sleeping (millisecs).
3127 Requires CONFIG_SCHEDSTATS
3128 Param: "kvm" - profile VM exits.
3129
3130 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3131 before loading.
3132 See Documentation/blockdev/ramdisk.txt.
3133
3134 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3135 probe for; one of (bare|imps|exps|lifebook|any).
3136 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3137 per second.
3138 psmouse.resetafter= [HW,MOUSE]
3139 Try to reset the device after so many bad packets
3140 (0 = never).
3141 psmouse.resolution=
3142 [HW,MOUSE] Set desired mouse resolution, in dpi.
3143 psmouse.smartscroll=
3144 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3145 0 = disabled, 1 = enabled (default).
3146
3147 pstore.backend= Specify the name of the pstore backend to use
3148
3149 pt. [PARIDE]
3150 See Documentation/blockdev/paride.txt.
3151
3152 pty.legacy_count=
3153 [KNL] Number of legacy pty's. Overwrites compiled-in
3154 default number.
3155
3156 quiet [KNL] Disable most log messages
3157
3158 r128= [HW,DRM]
3159
3160 raid= [HW,RAID]
3161 See Documentation/admin-guide/md.rst.
3162
3163 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3164 See Documentation/blockdev/ramdisk.txt.
3165
3166 rcu_nocbs= [KNL]
3167 The argument is a cpu list, as described above.
3168
3169 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3170 the specified list of CPUs to be no-callback CPUs.
3171 Invocation of these CPUs' RCU callbacks will
3172 be offloaded to "rcuox/N" kthreads created for
3173 that purpose, where "x" is "b" for RCU-bh, "p"
3174 for RCU-preempt, and "s" for RCU-sched, and "N"
3175 is the CPU number. This reduces OS jitter on the
3176 offloaded CPUs, which can be useful for HPC and
3177 real-time workloads. It can also improve energy
3178 efficiency for asymmetric multiprocessors.
3179
3180 rcu_nocb_poll [KNL]
3181 Rather than requiring that offloaded CPUs
3182 (specified by rcu_nocbs= above) explicitly
3183 awaken the corresponding "rcuoN" kthreads,
3184 make these kthreads poll for callbacks.
3185 This improves the real-time response for the
3186 offloaded CPUs by relieving them of the need to
3187 wake up the corresponding kthread, but degrades
3188 energy efficiency by requiring that the kthreads
3189 periodically wake up to do the polling.
3190
3191 rcutree.blimit= [KNL]
3192 Set maximum number of finished RCU callbacks to
3193 process in one batch.
3194
3195 rcutree.dump_tree= [KNL]
3196 Dump the structure of the rcu_node combining tree
3197 out at early boot. This is used for diagnostic
3198 purposes, to verify correct tree setup.
3199
3200 rcutree.gp_cleanup_delay= [KNL]
3201 Set the number of jiffies to delay each step of
3202 RCU grace-period cleanup. This only has effect
3203 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3204
3205 rcutree.gp_init_delay= [KNL]
3206 Set the number of jiffies to delay each step of
3207 RCU grace-period initialization. This only has
3208 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3209 is set.
3210
3211 rcutree.gp_preinit_delay= [KNL]
3212 Set the number of jiffies to delay each step of
3213 RCU grace-period pre-initialization, that is,
3214 the propagation of recent CPU-hotplug changes up
3215 the rcu_node combining tree. This only has effect
3216 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3217
3218 rcutree.rcu_fanout_exact= [KNL]
3219 Disable autobalancing of the rcu_node combining
3220 tree. This is used by rcutorture, and might
3221 possibly be useful for architectures having high
3222 cache-to-cache transfer latencies.
3223
3224 rcutree.rcu_fanout_leaf= [KNL]
3225 Change the number of CPUs assigned to each
3226 leaf rcu_node structure. Useful for very
3227 large systems, which will choose the value 64,
3228 and for NUMA systems with large remote-access
3229 latencies, which will choose a value aligned
3230 with the appropriate hardware boundaries.
3231
3232 rcutree.jiffies_till_sched_qs= [KNL]
3233 Set required age in jiffies for a
3234 given grace period before RCU starts
3235 soliciting quiescent-state help from
3236 rcu_note_context_switch().
3237
3238 rcutree.jiffies_till_first_fqs= [KNL]
3239 Set delay from grace-period initialization to
3240 first attempt to force quiescent states.
3241 Units are jiffies, minimum value is zero,
3242 and maximum value is HZ.
3243
3244 rcutree.jiffies_till_next_fqs= [KNL]
3245 Set delay between subsequent attempts to force
3246 quiescent states. Units are jiffies, minimum
3247 value is one, and maximum value is HZ.
3248
3249 rcutree.kthread_prio= [KNL,BOOT]
3250 Set the SCHED_FIFO priority of the RCU per-CPU
3251 kthreads (rcuc/N). This value is also used for
3252 the priority of the RCU boost threads (rcub/N)
3253 and for the RCU grace-period kthreads (rcu_bh,
3254 rcu_preempt, and rcu_sched). If RCU_BOOST is
3255 set, valid values are 1-99 and the default is 1
3256 (the least-favored priority). Otherwise, when
3257 RCU_BOOST is not set, valid values are 0-99 and
3258 the default is zero (non-realtime operation).
3259
3260 rcutree.rcu_nocb_leader_stride= [KNL]
3261 Set the number of NOCB kthread groups, which
3262 defaults to the square root of the number of
3263 CPUs. Larger numbers reduces the wakeup overhead
3264 on the per-CPU grace-period kthreads, but increases
3265 that same overhead on each group's leader.
3266
3267 rcutree.qhimark= [KNL]
3268 Set threshold of queued RCU callbacks beyond which
3269 batch limiting is disabled.
3270
3271 rcutree.qlowmark= [KNL]
3272 Set threshold of queued RCU callbacks below which
3273 batch limiting is re-enabled.
3274
3275 rcutree.rcu_idle_gp_delay= [KNL]
3276 Set wakeup interval for idle CPUs that have
3277 RCU callbacks (RCU_FAST_NO_HZ=y).
3278
3279 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3280 Set wakeup interval for idle CPUs that have
3281 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3282 Lazy RCU callbacks are those which RCU can
3283 prove do nothing more than free memory.
3284
3285 rcuperf.gp_exp= [KNL]
3286 Measure performance of expedited synchronous
3287 grace-period primitives.
3288
3289 rcuperf.holdoff= [KNL]
3290 Set test-start holdoff period. The purpose of
3291 this parameter is to delay the start of the
3292 test until boot completes in order to avoid
3293 interference.
3294
3295 rcuperf.nreaders= [KNL]
3296 Set number of RCU readers. The value -1 selects
3297 N, where N is the number of CPUs. A value
3298 "n" less than -1 selects N-n+1, where N is again
3299 the number of CPUs. For example, -2 selects N
3300 (the number of CPUs), -3 selects N+1, and so on.
3301 A value of "n" less than or equal to -N selects
3302 a single reader.
3303
3304 rcuperf.nwriters= [KNL]
3305 Set number of RCU writers. The values operate
3306 the same as for rcuperf.nreaders.
3307 N, where N is the number of CPUs
3308
3309 rcuperf.perf_runnable= [BOOT]
3310 Start rcuperf running at boot time.
3311
3312 rcuperf.shutdown= [KNL]
3313 Shut the system down after performance tests
3314 complete. This is useful for hands-off automated
3315 testing.
3316
3317 rcuperf.perf_type= [KNL]
3318 Specify the RCU implementation to test.
3319
3320 rcuperf.verbose= [KNL]
3321 Enable additional printk() statements.
3322
3323 rcutorture.cbflood_inter_holdoff= [KNL]
3324 Set holdoff time (jiffies) between successive
3325 callback-flood tests.
3326
3327 rcutorture.cbflood_intra_holdoff= [KNL]
3328 Set holdoff time (jiffies) between successive
3329 bursts of callbacks within a given callback-flood
3330 test.
3331
3332 rcutorture.cbflood_n_burst= [KNL]
3333 Set the number of bursts making up a given
3334 callback-flood test. Set this to zero to
3335 disable callback-flood testing.
3336
3337 rcutorture.cbflood_n_per_burst= [KNL]
3338 Set the number of callbacks to be registered
3339 in a given burst of a callback-flood test.
3340
3341 rcutorture.fqs_duration= [KNL]
3342 Set duration of force_quiescent_state bursts
3343 in microseconds.
3344
3345 rcutorture.fqs_holdoff= [KNL]
3346 Set holdoff time within force_quiescent_state bursts
3347 in microseconds.
3348
3349 rcutorture.fqs_stutter= [KNL]
3350 Set wait time between force_quiescent_state bursts
3351 in seconds.
3352
3353 rcutorture.gp_cond= [KNL]
3354 Use conditional/asynchronous update-side
3355 primitives, if available.
3356
3357 rcutorture.gp_exp= [KNL]
3358 Use expedited update-side primitives, if available.
3359
3360 rcutorture.gp_normal= [KNL]
3361 Use normal (non-expedited) asynchronous
3362 update-side primitives, if available.
3363
3364 rcutorture.gp_sync= [KNL]
3365 Use normal (non-expedited) synchronous
3366 update-side primitives, if available. If all
3367 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3368 rcutorture.gp_normal=, and rcutorture.gp_sync=
3369 are zero, rcutorture acts as if is interpreted
3370 they are all non-zero.
3371
3372 rcutorture.n_barrier_cbs= [KNL]
3373 Set callbacks/threads for rcu_barrier() testing.
3374
3375 rcutorture.nfakewriters= [KNL]
3376 Set number of concurrent RCU writers. These just
3377 stress RCU, they don't participate in the actual
3378 test, hence the "fake".
3379
3380 rcutorture.nreaders= [KNL]
3381 Set number of RCU readers. The value -1 selects
3382 N-1, where N is the number of CPUs. A value
3383 "n" less than -1 selects N-n-2, where N is again
3384 the number of CPUs. For example, -2 selects N
3385 (the number of CPUs), -3 selects N+1, and so on.
3386
3387 rcutorture.object_debug= [KNL]
3388 Enable debug-object double-call_rcu() testing.
3389
3390 rcutorture.onoff_holdoff= [KNL]
3391 Set time (s) after boot for CPU-hotplug testing.
3392
3393 rcutorture.onoff_interval= [KNL]
3394 Set time (s) between CPU-hotplug operations, or
3395 zero to disable CPU-hotplug testing.
3396
3397 rcutorture.shuffle_interval= [KNL]
3398 Set task-shuffle interval (s). Shuffling tasks
3399 allows some CPUs to go into dyntick-idle mode
3400 during the rcutorture test.
3401
3402 rcutorture.shutdown_secs= [KNL]
3403 Set time (s) after boot system shutdown. This
3404 is useful for hands-off automated testing.
3405
3406 rcutorture.stall_cpu= [KNL]
3407 Duration of CPU stall (s) to test RCU CPU stall
3408 warnings, zero to disable.
3409
3410 rcutorture.stall_cpu_holdoff= [KNL]
3411 Time to wait (s) after boot before inducing stall.
3412
3413 rcutorture.stat_interval= [KNL]
3414 Time (s) between statistics printk()s.
3415
3416 rcutorture.stutter= [KNL]
3417 Time (s) to stutter testing, for example, specifying
3418 five seconds causes the test to run for five seconds,
3419 wait for five seconds, and so on. This tests RCU's
3420 ability to transition abruptly to and from idle.
3421
3422 rcutorture.test_boost= [KNL]
3423 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3424 "Maybe" means test if the RCU implementation
3425 under test support RCU priority boosting.
3426
3427 rcutorture.test_boost_duration= [KNL]
3428 Duration (s) of each individual boost test.
3429
3430 rcutorture.test_boost_interval= [KNL]
3431 Interval (s) between each boost test.
3432
3433 rcutorture.test_no_idle_hz= [KNL]
3434 Test RCU's dyntick-idle handling. See also the
3435 rcutorture.shuffle_interval parameter.
3436
3437 rcutorture.torture_runnable= [BOOT]
3438 Start rcutorture running at boot time.
3439
3440 rcutorture.torture_type= [KNL]
3441 Specify the RCU implementation to test.
3442
3443 rcutorture.verbose= [KNL]
3444 Enable additional printk() statements.
3445
3446 rcupdate.rcu_cpu_stall_suppress= [KNL]
3447 Suppress RCU CPU stall warning messages.
3448
3449 rcupdate.rcu_cpu_stall_timeout= [KNL]
3450 Set timeout for RCU CPU stall warning messages.
3451
3452 rcupdate.rcu_expedited= [KNL]
3453 Use expedited grace-period primitives, for
3454 example, synchronize_rcu_expedited() instead
3455 of synchronize_rcu(). This reduces latency,
3456 but can increase CPU utilization, degrade
3457 real-time latency, and degrade energy efficiency.
3458 No effect on CONFIG_TINY_RCU kernels.
3459
3460 rcupdate.rcu_normal= [KNL]
3461 Use only normal grace-period primitives,
3462 for example, synchronize_rcu() instead of
3463 synchronize_rcu_expedited(). This improves
3464 real-time latency, CPU utilization, and
3465 energy efficiency, but can expose users to
3466 increased grace-period latency. This parameter
3467 overrides rcupdate.rcu_expedited. No effect on
3468 CONFIG_TINY_RCU kernels.
3469
3470 rcupdate.rcu_normal_after_boot= [KNL]
3471 Once boot has completed (that is, after
3472 rcu_end_inkernel_boot() has been invoked), use
3473 only normal grace-period primitives. No effect
3474 on CONFIG_TINY_RCU kernels.
3475
3476 rcupdate.rcu_task_stall_timeout= [KNL]
3477 Set timeout in jiffies for RCU task stall warning
3478 messages. Disable with a value less than or equal
3479 to zero.
3480
3481 rcupdate.rcu_self_test= [KNL]
3482 Run the RCU early boot self tests
3483
3484 rcupdate.rcu_self_test_bh= [KNL]
3485 Run the RCU bh early boot self tests
3486
3487 rcupdate.rcu_self_test_sched= [KNL]
3488 Run the RCU sched early boot self tests
3489
3490 rdinit= [KNL]
3491 Format: <full_path>
3492 Run specified binary instead of /init from the ramdisk,
3493 used for early userspace startup. See initrd.
3494
3495 reboot= [KNL]
3496 Format (x86 or x86_64):
3497 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3498 [[,]s[mp]#### \
3499 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3500 [[,]f[orce]
3501 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3502 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3503 reboot_force is either force or not specified,
3504 reboot_cpu is s[mp]#### with #### being the processor
3505 to be used for rebooting.
3506
3507 relax_domain_level=
3508 [KNL, SMP] Set scheduler's default relax_domain_level.
3509 See Documentation/cgroup-v1/cpusets.txt.
3510
3511 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3512
3513 reservetop= [X86-32]
3514 Format: nn[KMG]
3515 Reserves a hole at the top of the kernel virtual
3516 address space.
3517
3518 reservelow= [X86]
3519 Format: nn[K]
3520 Set the amount of memory to reserve for BIOS at
3521 the bottom of the address space.
3522
3523 reset_devices [KNL] Force drivers to reset the underlying device
3524 during initialization.
3525
3526 resume= [SWSUSP]
3527 Specify the partition device for software suspend
3528 Format:
3529 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3530
3531 resume_offset= [SWSUSP]
3532 Specify the offset from the beginning of the partition
3533 given by "resume=" at which the swap header is located,
3534 in <PAGE_SIZE> units (needed only for swap files).
3535 See Documentation/power/swsusp-and-swap-files.txt
3536
3537 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3538 read the resume files
3539
3540 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3541 Useful for devices that are detected asynchronously
3542 (e.g. USB and MMC devices).
3543
3544 hibernate= [HIBERNATION]
3545 noresume Don't check if there's a hibernation image
3546 present during boot.
3547 nocompress Don't compress/decompress hibernation images.
3548 no Disable hibernation and resume.
3549 protect_image Turn on image protection during restoration
3550 (that will set all pages holding image data
3551 during restoration read-only).
3552
3553 retain_initrd [RAM] Keep initrd memory after extraction
3554
3555 rfkill.default_state=
3556 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3557 etc. communication is blocked by default.
3558 1 Unblocked.
3559
3560 rfkill.master_switch_mode=
3561 0 The "airplane mode" button does nothing.
3562 1 The "airplane mode" button toggles between everything
3563 blocked and the previous configuration.
3564 2 The "airplane mode" button toggles between everything
3565 blocked and everything unblocked.
3566
3567 rhash_entries= [KNL,NET]
3568 Set number of hash buckets for route cache
3569
3570 ro [KNL] Mount root device read-only on boot
3571
3572 rodata= [KNL]
3573 on Mark read-only kernel memory as read-only (default).
3574 off Leave read-only kernel memory writable for debugging.
3575
3576 rockchip.usb_uart
3577 Enable the uart passthrough on the designated usb port
3578 on Rockchip SoCs. When active, the signals of the
3579 debug-uart get routed to the D+ and D- pins of the usb
3580 port and the regular usb controller gets disabled.
3581
3582 root= [KNL] Root filesystem
3583 See name_to_dev_t comment in init/do_mounts.c.
3584
3585 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3586 mount the root filesystem
3587
3588 rootflags= [KNL] Set root filesystem mount option string
3589
3590 rootfstype= [KNL] Set root filesystem type
3591
3592 rootwait [KNL] Wait (indefinitely) for root device to show up.
3593 Useful for devices that are detected asynchronously
3594 (e.g. USB and MMC devices).
3595
3596 rproc_mem=nn[KMG][@address]
3597 [KNL,ARM,CMA] Remoteproc physical memory block.
3598 Memory area to be used by remote processor image,
3599 managed by CMA.
3600
3601 rw [KNL] Mount root device read-write on boot
3602
3603 S [KNL] Run init in single mode
3604
3605 s390_iommu= [HW,S390]
3606 Set s390 IOTLB flushing mode
3607 strict
3608 With strict flushing every unmap operation will result in
3609 an IOTLB flush. Default is lazy flushing before reuse,
3610 which is faster.
3611
3612 sa1100ir [NET]
3613 See drivers/net/irda/sa1100_ir.c.
3614
3615 sbni= [NET] Granch SBNI12 leased line adapter
3616
3617 sched_debug [KNL] Enables verbose scheduler debug messages.
3618
3619 schedstats= [KNL,X86] Enable or disable scheduled statistics.
3620 Allowed values are enable and disable. This feature
3621 incurs a small amount of overhead in the scheduler
3622 but is useful for debugging and performance tuning.
3623
3624 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3625 xtime_lock contention on larger systems, and/or RCU lock
3626 contention on all systems with CONFIG_MAXSMP set.
3627 Format: { "0" | "1" }
3628 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3629 1 -- enable.
3630 Note: increases power consumption, thus should only be
3631 enabled if running jitter sensitive (HPC/RT) workloads.
3632
3633 security= [SECURITY] Choose a security module to enable at boot.
3634 If this boot parameter is not specified, only the first
3635 security module asking for security registration will be
3636 loaded. An invalid security module name will be treated
3637 as if no module has been chosen.
3638
3639 selinux= [SELINUX] Disable or enable SELinux at boot time.
3640 Format: { "0" | "1" }
3641 See security/selinux/Kconfig help text.
3642 0 -- disable.
3643 1 -- enable.
3644 Default value is set via kernel config option.
3645 If enabled at boot time, /selinux/disable can be used
3646 later to disable prior to initial policy load.
3647
3648 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3649 Format: { "0" | "1" }
3650 See security/apparmor/Kconfig help text
3651 0 -- disable.
3652 1 -- enable.
3653 Default value is set via kernel config option.
3654
3655 serialnumber [BUGS=X86-32]
3656
3657 shapers= [NET]
3658 Maximal number of shapers.
3659
3660 simeth= [IA-64]
3661 simscsi=
3662
3663 slram= [HW,MTD]
3664
3665 slab_nomerge [MM]
3666 Disable merging of slabs with similar size. May be
3667 necessary if there is some reason to distinguish
3668 allocs to different slabs. Debug options disable
3669 merging on their own.
3670 For more information see Documentation/vm/slub.txt.
3671
3672 slab_max_order= [MM, SLAB]
3673 Determines the maximum allowed order for slabs.
3674 A high setting may cause OOMs due to memory
3675 fragmentation. Defaults to 1 for systems with
3676 more than 32MB of RAM, 0 otherwise.
3677
3678 slub_debug[=options[,slabs]] [MM, SLUB]
3679 Enabling slub_debug allows one to determine the
3680 culprit if slab objects become corrupted. Enabling
3681 slub_debug can create guard zones around objects and
3682 may poison objects when not in use. Also tracks the
3683 last alloc / free. For more information see
3684 Documentation/vm/slub.txt.
3685
3686 slub_max_order= [MM, SLUB]
3687 Determines the maximum allowed order for slabs.
3688 A high setting may cause OOMs due to memory
3689 fragmentation. For more information see
3690 Documentation/vm/slub.txt.
3691
3692 slub_min_objects= [MM, SLUB]
3693 The minimum number of objects per slab. SLUB will
3694 increase the slab order up to slub_max_order to
3695 generate a sufficiently large slab able to contain
3696 the number of objects indicated. The higher the number
3697 of objects the smaller the overhead of tracking slabs
3698 and the less frequently locks need to be acquired.
3699 For more information see Documentation/vm/slub.txt.
3700
3701 slub_min_order= [MM, SLUB]
3702 Determines the minimum page order for slabs. Must be
3703 lower than slub_max_order.
3704 For more information see Documentation/vm/slub.txt.
3705
3706 slub_nomerge [MM, SLUB]
3707 Same with slab_nomerge. This is supported for legacy.
3708 See slab_nomerge for more information.
3709
3710 smart2= [HW]
3711 Format: <io1>[,<io2>[,...,<io8>]]
3712
3713 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3714 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3715 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3716 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3717 smsc-ircc2.ircc_irq= [HW] IRQ line
3718 smsc-ircc2.ircc_dma= [HW] DMA channel
3719 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3720 0: Toshiba Satellite 1800 (GP data pin select)
3721 1: Fast pin select (default)
3722 2: ATC IRMode
3723
3724 smt [KNL,S390] Set the maximum number of threads (logical
3725 CPUs) to use per physical CPU on systems capable of
3726 symmetric multithreading (SMT). Will be capped to the
3727 actual hardware limit.
3728 Format: <integer>
3729 Default: -1 (no limit)
3730
3731 softlockup_panic=
3732 [KNL] Should the soft-lockup detector generate panics.
3733 Format: <integer>
3734
3735 softlockup_all_cpu_backtrace=
3736 [KNL] Should the soft-lockup detector generate
3737 backtraces on all cpus.
3738 Format: <integer>
3739
3740 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3741 See Documentation/laptops/sonypi.txt
3742
3743 spia_io_base= [HW,MTD]
3744 spia_fio_base=
3745 spia_pedr=
3746 spia_peddr=
3747
3748 stacktrace [FTRACE]
3749 Enabled the stack tracer on boot up.
3750
3751 stacktrace_filter=[function-list]
3752 [FTRACE] Limit the functions that the stack tracer
3753 will trace at boot up. function-list is a comma separated
3754 list of functions. This list can be changed at run
3755 time by the stack_trace_filter file in the debugfs
3756 tracing directory. Note, this enables stack tracing
3757 and the stacktrace above is not needed.
3758
3759 sti= [PARISC,HW]
3760 Format: <num>
3761 Set the STI (builtin display/keyboard on the HP-PARISC
3762 machines) console (graphic card) which should be used
3763 as the initial boot-console.
3764 See also comment in drivers/video/console/sticore.c.
3765
3766 sti_font= [HW]
3767 See comment in drivers/video/console/sticore.c.
3768
3769 stifb= [HW]
3770 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3771
3772 sunrpc.min_resvport=
3773 sunrpc.max_resvport=
3774 [NFS,SUNRPC]
3775 SunRPC servers often require that client requests
3776 originate from a privileged port (i.e. a port in the
3777 range 0 < portnr < 1024).
3778 An administrator who wishes to reserve some of these
3779 ports for other uses may adjust the range that the
3780 kernel's sunrpc client considers to be privileged
3781 using these two parameters to set the minimum and
3782 maximum port values.
3783
3784 sunrpc.svc_rpc_per_connection_limit=
3785 [NFS,SUNRPC]
3786 Limit the number of requests that the server will
3787 process in parallel from a single connection.
3788 The default value is 0 (no limit).
3789
3790 sunrpc.pool_mode=
3791 [NFS]
3792 Control how the NFS server code allocates CPUs to
3793 service thread pools. Depending on how many NICs
3794 you have and where their interrupts are bound, this
3795 option will affect which CPUs will do NFS serving.
3796 Note: this parameter cannot be changed while the
3797 NFS server is running.
3798
3799 auto the server chooses an appropriate mode
3800 automatically using heuristics
3801 global a single global pool contains all CPUs
3802 percpu one pool for each CPU
3803 pernode one pool for each NUMA node (equivalent
3804 to global on non-NUMA machines)
3805
3806 sunrpc.tcp_slot_table_entries=
3807 sunrpc.udp_slot_table_entries=
3808 [NFS,SUNRPC]
3809 Sets the upper limit on the number of simultaneous
3810 RPC calls that can be sent from the client to a
3811 server. Increasing these values may allow you to
3812 improve throughput, but will also increase the
3813 amount of memory reserved for use by the client.
3814
3815 suspend.pm_test_delay=
3816 [SUSPEND]
3817 Sets the number of seconds to remain in a suspend test
3818 mode before resuming the system (see
3819 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3820 is set. Default value is 5.
3821
3822 swapaccount=[0|1]
3823 [KNL] Enable accounting of swap in memory resource
3824 controller if no parameter or 1 is given or disable
3825 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
3826
3827 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3828 Format: { <int> | force | noforce }
3829 <int> -- Number of I/O TLB slabs
3830 force -- force using of bounce buffers even if they
3831 wouldn't be automatically used by the kernel
3832 noforce -- Never use bounce buffers (for debugging)
3833
3834 switches= [HW,M68k]
3835
3836 sysfs.deprecated=0|1 [KNL]
3837 Enable/disable old style sysfs layout for old udev
3838 on older distributions. When this option is enabled
3839 very new udev will not work anymore. When this option
3840 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3841 in older udev will not work anymore.
3842 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3843 the kernel configuration.
3844
3845 sysrq_always_enabled
3846 [KNL]
3847 Ignore sysrq setting - this boot parameter will
3848 neutralize any effect of /proc/sys/kernel/sysrq.
3849 Useful for debugging.
3850
3851 tcpmhash_entries= [KNL,NET]
3852 Set the number of tcp_metrics_hash slots.
3853 Default value is 8192 or 16384 depending on total
3854 ram pages. This is used to specify the TCP metrics
3855 cache size. See Documentation/networking/ip-sysctl.txt
3856 "tcp_no_metrics_save" section for more details.
3857
3858 tdfx= [HW,DRM]
3859
3860 test_suspend= [SUSPEND][,N]
3861 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3862 standby suspend) or "freeze" (for suspend type freeze)
3863 as the system sleep state during system startup with
3864 the optional capability to repeat N number of times.
3865 The system is woken from this state using a
3866 wakeup-capable RTC alarm.
3867
3868 thash_entries= [KNL,NET]
3869 Set number of hash buckets for TCP connection
3870
3871 thermal.act= [HW,ACPI]
3872 -1: disable all active trip points in all thermal zones
3873 <degrees C>: override all lowest active trip points
3874
3875 thermal.crt= [HW,ACPI]
3876 -1: disable all critical trip points in all thermal zones
3877 <degrees C>: override all critical trip points
3878
3879 thermal.nocrt= [HW,ACPI]
3880 Set to disable actions on ACPI thermal zone
3881 critical and hot trip points.
3882
3883 thermal.off= [HW,ACPI]
3884 1: disable ACPI thermal control
3885
3886 thermal.psv= [HW,ACPI]
3887 -1: disable all passive trip points
3888 <degrees C>: override all passive trip points to this
3889 value
3890
3891 thermal.tzp= [HW,ACPI]
3892 Specify global default ACPI thermal zone polling rate
3893 <deci-seconds>: poll all this frequency
3894 0: no polling (default)
3895
3896 threadirqs [KNL]
3897 Force threading of all interrupt handlers except those
3898 marked explicitly IRQF_NO_THREAD.
3899
3900 tmem [KNL,XEN]
3901 Enable the Transcendent memory driver if built-in.
3902
3903 tmem.cleancache=0|1 [KNL, XEN]
3904 Default is on (1). Disable the usage of the cleancache
3905 API to send anonymous pages to the hypervisor.
3906
3907 tmem.frontswap=0|1 [KNL, XEN]
3908 Default is on (1). Disable the usage of the frontswap
3909 API to send swap pages to the hypervisor. If disabled
3910 the selfballooning and selfshrinking are force disabled.
3911
3912 tmem.selfballooning=0|1 [KNL, XEN]
3913 Default is on (1). Disable the driving of swap pages
3914 to the hypervisor.
3915
3916 tmem.selfshrinking=0|1 [KNL, XEN]
3917 Default is on (1). Partial swapoff that immediately
3918 transfers pages from Xen hypervisor back to the
3919 kernel based on different criteria.
3920
3921 topology= [S390]
3922 Format: {off | on}
3923 Specify if the kernel should make use of the cpu
3924 topology information if the hardware supports this.
3925 The scheduler will make use of this information and
3926 e.g. base its process migration decisions on it.
3927 Default is on.
3928
3929 topology_updates= [KNL, PPC, NUMA]
3930 Format: {off}
3931 Specify if the kernel should ignore (off)
3932 topology updates sent by the hypervisor to this
3933 LPAR.
3934
3935 tp720= [HW,PS2]
3936
3937 tpm_suspend_pcr=[HW,TPM]
3938 Format: integer pcr id
3939 Specify that at suspend time, the tpm driver
3940 should extend the specified pcr with zeros,
3941 as a workaround for some chips which fail to
3942 flush the last written pcr on TPM_SaveState.
3943 This will guarantee that all the other pcrs
3944 are saved.
3945
3946 trace_buf_size=nn[KMG]
3947 [FTRACE] will set tracing buffer size on each cpu.
3948
3949 trace_event=[event-list]
3950 [FTRACE] Set and start specified trace events in order
3951 to facilitate early boot debugging. The event-list is a
3952 comma separated list of trace events to enable. See
3953 also Documentation/trace/events.txt
3954
3955 trace_options=[option-list]
3956 [FTRACE] Enable or disable tracer options at boot.
3957 The option-list is a comma delimited list of options
3958 that can be enabled or disabled just as if you were
3959 to echo the option name into
3960
3961 /sys/kernel/debug/tracing/trace_options
3962
3963 For example, to enable stacktrace option (to dump the
3964 stack trace of each event), add to the command line:
3965
3966 trace_options=stacktrace
3967
3968 See also Documentation/trace/ftrace.txt "trace options"
3969 section.
3970
3971 tp_printk[FTRACE]
3972 Have the tracepoints sent to printk as well as the
3973 tracing ring buffer. This is useful for early boot up
3974 where the system hangs or reboots and does not give the
3975 option for reading the tracing buffer or performing a
3976 ftrace_dump_on_oops.
3977
3978 To turn off having tracepoints sent to printk,
3979 echo 0 > /proc/sys/kernel/tracepoint_printk
3980 Note, echoing 1 into this file without the
3981 tracepoint_printk kernel cmdline option has no effect.
3982
3983 ** CAUTION **
3984
3985 Having tracepoints sent to printk() and activating high
3986 frequency tracepoints such as irq or sched, can cause
3987 the system to live lock.
3988
3989 traceoff_on_warning
3990 [FTRACE] enable this option to disable tracing when a
3991 warning is hit. This turns off "tracing_on". Tracing can
3992 be enabled again by echoing '1' into the "tracing_on"
3993 file located in /sys/kernel/debug/tracing/
3994
3995 This option is useful, as it disables the trace before
3996 the WARNING dump is called, which prevents the trace to
3997 be filled with content caused by the warning output.
3998
3999 This option can also be set at run time via the sysctl
4000 option: kernel/traceoff_on_warning
4001
4002 transparent_hugepage=
4003 [KNL]
4004 Format: [always|madvise|never]
4005 Can be used to control the default behavior of the system
4006 with respect to transparent hugepages.
4007 See Documentation/vm/transhuge.txt for more details.
4008
4009 tsc= Disable clocksource stability checks for TSC.
4010 Format: <string>
4011 [x86] reliable: mark tsc clocksource as reliable, this
4012 disables clocksource verification at runtime, as well
4013 as the stability checks done at bootup. Used to enable
4014 high-resolution timer mode on older hardware, and in
4015 virtualized environment.
4016 [x86] noirqtime: Do not use TSC to do irq accounting.
4017 Used to run time disable IRQ_TIME_ACCOUNTING on any
4018 platforms where RDTSC is slow and this accounting
4019 can add overhead.
4020
4021 turbografx.map[2|3]= [HW,JOY]
4022 TurboGraFX parallel port interface
4023 Format:
4024 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4025 See also Documentation/input/joystick-parport.txt
4026
4027 udbg-immortal [PPC] When debugging early kernel crashes that
4028 happen after console_init() and before a proper
4029 console driver takes over, this boot options might
4030 help "seeing" what's going on.
4031
4032 uhash_entries= [KNL,NET]
4033 Set number of hash buckets for UDP/UDP-Lite connections
4034
4035 uhci-hcd.ignore_oc=
4036 [USB] Ignore overcurrent events (default N).
4037 Some badly-designed motherboards generate lots of
4038 bogus events, for ports that aren't wired to
4039 anything. Set this parameter to avoid log spamming.
4040 Note that genuine overcurrent events won't be
4041 reported either.
4042
4043 unknown_nmi_panic
4044 [X86] Cause panic on unknown NMI.
4045
4046 usbcore.authorized_default=
4047 [USB] Default USB device authorization:
4048 (default -1 = authorized except for wireless USB,
4049 0 = not authorized, 1 = authorized)
4050
4051 usbcore.autosuspend=
4052 [USB] The autosuspend time delay (in seconds) used
4053 for newly-detected USB devices (default 2). This
4054 is the time required before an idle device will be
4055 autosuspended. Devices for which the delay is set
4056 to a negative value won't be autosuspended at all.
4057
4058 usbcore.usbfs_snoop=
4059 [USB] Set to log all usbfs traffic (default 0 = off).
4060
4061 usbcore.usbfs_snoop_max=
4062 [USB] Maximum number of bytes to snoop in each URB
4063 (default = 65536).
4064
4065 usbcore.blinkenlights=
4066 [USB] Set to cycle leds on hubs (default 0 = off).
4067
4068 usbcore.old_scheme_first=
4069 [USB] Start with the old device initialization
4070 scheme (default 0 = off).
4071
4072 usbcore.usbfs_memory_mb=
4073 [USB] Memory limit (in MB) for buffers allocated by
4074 usbfs (default = 16, 0 = max = 2047).
4075
4076 usbcore.use_both_schemes=
4077 [USB] Try the other device initialization scheme
4078 if the first one fails (default 1 = enabled).
4079
4080 usbcore.initial_descriptor_timeout=
4081 [USB] Specifies timeout for the initial 64-byte
4082 USB_REQ_GET_DESCRIPTOR request in milliseconds
4083 (default 5000 = 5.0 seconds).
4084
4085 usbcore.nousb [USB] Disable the USB subsystem
4086
4087 usbhid.mousepoll=
4088 [USBHID] The interval which mice are to be polled at.
4089
4090 usb-storage.delay_use=
4091 [UMS] The delay in seconds before a new device is
4092 scanned for Logical Units (default 1).
4093
4094 usb-storage.quirks=
4095 [UMS] A list of quirks entries to supplement or
4096 override the built-in unusual_devs list. List
4097 entries are separated by commas. Each entry has
4098 the form VID:PID:Flags where VID and PID are Vendor
4099 and Product ID values (4-digit hex numbers) and
4100 Flags is a set of characters, each corresponding
4101 to a common usb-storage quirk flag as follows:
4102 a = SANE_SENSE (collect more than 18 bytes
4103 of sense data);
4104 b = BAD_SENSE (don't collect more than 18
4105 bytes of sense data);
4106 c = FIX_CAPACITY (decrease the reported
4107 device capacity by one sector);
4108 d = NO_READ_DISC_INFO (don't use
4109 READ_DISC_INFO command);
4110 e = NO_READ_CAPACITY_16 (don't use
4111 READ_CAPACITY_16 command);
4112 f = NO_REPORT_OPCODES (don't use report opcodes
4113 command, uas only);
4114 g = MAX_SECTORS_240 (don't transfer more than
4115 240 sectors at a time, uas only);
4116 h = CAPACITY_HEURISTICS (decrease the
4117 reported device capacity by one
4118 sector if the number is odd);
4119 i = IGNORE_DEVICE (don't bind to this
4120 device);
4121 j = NO_REPORT_LUNS (don't use report luns
4122 command, uas only);
4123 l = NOT_LOCKABLE (don't try to lock and
4124 unlock ejectable media);
4125 m = MAX_SECTORS_64 (don't transfer more
4126 than 64 sectors = 32 KB at a time);
4127 n = INITIAL_READ10 (force a retry of the
4128 initial READ(10) command);
4129 o = CAPACITY_OK (accept the capacity
4130 reported by the device);
4131 p = WRITE_CACHE (the device cache is ON
4132 by default);
4133 r = IGNORE_RESIDUE (the device reports
4134 bogus residue values);
4135 s = SINGLE_LUN (the device has only one
4136 Logical Unit);
4137 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4138 commands, uas only);
4139 u = IGNORE_UAS (don't bind to the uas driver);
4140 w = NO_WP_DETECT (don't test whether the
4141 medium is write-protected).
4142 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4143 even if the device claims no cache)
4144 Example: quirks=0419:aaf5:rl,0421:0433:rc
4145
4146 user_debug= [KNL,ARM]
4147 Format: <int>
4148 See arch/arm/Kconfig.debug help text.
4149 1 - undefined instruction events
4150 2 - system calls
4151 4 - invalid data aborts
4152 8 - SIGSEGV faults
4153 16 - SIGBUS faults
4154 Example: user_debug=31
4155
4156 userpte=
4157 [X86] Flags controlling user PTE allocations.
4158
4159 nohigh = do not allocate PTE pages in
4160 HIGHMEM regardless of setting
4161 of CONFIG_HIGHPTE.
4162
4163 vdso= [X86,SH]
4164 On X86_32, this is an alias for vdso32=. Otherwise:
4165
4166 vdso=1: enable VDSO (the default)
4167 vdso=0: disable VDSO mapping
4168
4169 vdso32= [X86] Control the 32-bit vDSO
4170 vdso32=1: enable 32-bit VDSO
4171 vdso32=0 or vdso32=2: disable 32-bit VDSO
4172
4173 See the help text for CONFIG_COMPAT_VDSO for more
4174 details. If CONFIG_COMPAT_VDSO is set, the default is
4175 vdso32=0; otherwise, the default is vdso32=1.
4176
4177 For compatibility with older kernels, vdso32=2 is an
4178 alias for vdso32=0.
4179
4180 Try vdso32=0 if you encounter an error that says:
4181 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4182
4183 vector= [IA-64,SMP]
4184 vector=percpu: enable percpu vector domain
4185
4186 video= [FB] Frame buffer configuration
4187 See Documentation/fb/modedb.txt.
4188
4189 video.brightness_switch_enabled= [0,1]
4190 If set to 1, on receiving an ACPI notify event
4191 generated by hotkey, video driver will adjust brightness
4192 level and then send out the event to user space through
4193 the allocated input device; If set to 0, video driver
4194 will only send out the event without touching backlight
4195 brightness level.
4196 default: 1
4197
4198 virtio_mmio.device=
4199 [VMMIO] Memory mapped virtio (platform) device.
4200
4201 <size>@<baseaddr>:<irq>[:<id>]
4202 where:
4203 <size> := size (can use standard suffixes
4204 like K, M and G)
4205 <baseaddr> := physical base address
4206 <irq> := interrupt number (as passed to
4207 request_irq())
4208 <id> := (optional) platform device id
4209 example:
4210 virtio_mmio.device=1K@0x100b0000:48:7
4211
4212 Can be used multiple times for multiple devices.
4213
4214 vga= [BOOT,X86-32] Select a particular video mode
4215 See Documentation/x86/boot.txt and
4216 Documentation/svga.txt.
4217 Use vga=ask for menu.
4218 This is actually a boot loader parameter; the value is
4219 passed to the kernel using a special protocol.
4220
4221 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4222 size of <nn>. This can be used to increase the
4223 minimum size (128MB on x86). It can also be used to
4224 decrease the size and leave more room for directly
4225 mapped kernel RAM.
4226
4227 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4228 Format: <command>
4229
4230 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4231 Format: <command>
4232
4233 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4234 Format: <command>
4235
4236 vsyscall= [X86-64]
4237 Controls the behavior of vsyscalls (i.e. calls to
4238 fixed addresses of 0xffffffffff600x00 from legacy
4239 code). Most statically-linked binaries and older
4240 versions of glibc use these calls. Because these
4241 functions are at fixed addresses, they make nice
4242 targets for exploits that can control RIP.
4243
4244 emulate [default] Vsyscalls turn into traps and are
4245 emulated reasonably safely.
4246
4247 native Vsyscalls are native syscall instructions.
4248 This is a little bit faster than trapping
4249 and makes a few dynamic recompilers work
4250 better than they would in emulation mode.
4251 It also makes exploits much easier to write.
4252
4253 none Vsyscalls don't work at all. This makes
4254 them quite hard to use for exploits but
4255 might break your system.
4256
4257 vt.color= [VT] Default text color.
4258 Format: 0xYX, X = foreground, Y = background.
4259 Default: 0x07 = light gray on black.
4260
4261 vt.cur_default= [VT] Default cursor shape.
4262 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4263 the parameters of the <Esc>[?A;B;Cc escape sequence;
4264 see VGA-softcursor.txt. Default: 2 = underline.
4265
4266 vt.default_blu= [VT]
4267 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4268 Change the default blue palette of the console.
4269 This is a 16-member array composed of values
4270 ranging from 0-255.
4271
4272 vt.default_grn= [VT]
4273 Format: <green0>,<green1>,<green2>,...,<green15>
4274 Change the default green palette of the console.
4275 This is a 16-member array composed of values
4276 ranging from 0-255.
4277
4278 vt.default_red= [VT]
4279 Format: <red0>,<red1>,<red2>,...,<red15>
4280 Change the default red palette of the console.
4281 This is a 16-member array composed of values
4282 ranging from 0-255.
4283
4284 vt.default_utf8=
4285 [VT]
4286 Format=<0|1>
4287 Set system-wide default UTF-8 mode for all tty's.
4288 Default is 1, i.e. UTF-8 mode is enabled for all
4289 newly opened terminals.
4290
4291 vt.global_cursor_default=
4292 [VT]
4293 Format=<-1|0|1>
4294 Set system-wide default for whether a cursor
4295 is shown on new VTs. Default is -1,
4296 i.e. cursors will be created by default unless
4297 overridden by individual drivers. 0 will hide
4298 cursors, 1 will display them.
4299
4300 vt.italic= [VT] Default color for italic text; 0-15.
4301 Default: 2 = green.
4302
4303 vt.underline= [VT] Default color for underlined text; 0-15.
4304 Default: 3 = cyan.
4305
4306 watchdog timers [HW,WDT] For information on watchdog timers,
4307 see Documentation/watchdog/watchdog-parameters.txt
4308 or other driver-specific files in the
4309 Documentation/watchdog/ directory.
4310
4311 workqueue.watchdog_thresh=
4312 If CONFIG_WQ_WATCHDOG is configured, workqueue can
4313 warn stall conditions and dump internal state to
4314 help debugging. 0 disables workqueue stall
4315 detection; otherwise, it's the stall threshold
4316 duration in seconds. The default value is 30 and
4317 it can be updated at runtime by writing to the
4318 corresponding sysfs file.
4319
4320 workqueue.disable_numa
4321 By default, all work items queued to unbound
4322 workqueues are affine to the NUMA nodes they're
4323 issued on, which results in better behavior in
4324 general. If NUMA affinity needs to be disabled for
4325 whatever reason, this option can be used. Note
4326 that this also can be controlled per-workqueue for
4327 workqueues visible under /sys/bus/workqueue/.
4328
4329 workqueue.power_efficient
4330 Per-cpu workqueues are generally preferred because
4331 they show better performance thanks to cache
4332 locality; unfortunately, per-cpu workqueues tend to
4333 be more power hungry than unbound workqueues.
4334
4335 Enabling this makes the per-cpu workqueues which
4336 were observed to contribute significantly to power
4337 consumption unbound, leading to measurably lower
4338 power usage at the cost of small performance
4339 overhead.
4340
4341 The default value of this parameter is determined by
4342 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4343
4344 workqueue.debug_force_rr_cpu
4345 Workqueue used to implicitly guarantee that work
4346 items queued without explicit CPU specified are put
4347 on the local CPU. This guarantee is no longer true
4348 and while local CPU is still preferred work items
4349 may be put on foreign CPUs. This debug option
4350 forces round-robin CPU selection to flush out
4351 usages which depend on the now broken guarantee.
4352 When enabled, memory and cache locality will be
4353 impacted.
4354
4355 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4356 default x2apic cluster mode on platforms
4357 supporting x2apic.
4358
4359 x86_intel_mid_timer= [X86-32,APBT]
4360 Choose timer option for x86 Intel MID platform.
4361 Two valid options are apbt timer only and lapic timer
4362 plus one apbt timer for broadcast timer.
4363 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4364
4365 xen_512gb_limit [KNL,X86-64,XEN]
4366 Restricts the kernel running paravirtualized under Xen
4367 to use only up to 512 GB of RAM. The reason to do so is
4368 crash analysis tools and Xen tools for doing domain
4369 save/restore/migration must be enabled to handle larger
4370 domains.
4371
4372 xen_emul_unplug= [HW,X86,XEN]
4373 Unplug Xen emulated devices
4374 Format: [unplug0,][unplug1]
4375 ide-disks -- unplug primary master IDE devices
4376 aux-ide-disks -- unplug non-primary-master IDE devices
4377 nics -- unplug network devices
4378 all -- unplug all emulated devices (NICs and IDE disks)
4379 unnecessary -- unplugging emulated devices is
4380 unnecessary even if the host did not respond to
4381 the unplug protocol
4382 never -- do not unplug even if version check succeeds
4383
4384 xen_nopvspin [X86,XEN]
4385 Disables the ticketlock slowpath using Xen PV
4386 optimizations.
4387
4388 xen_nopv [X86]
4389 Disables the PV optimizations forcing the HVM guest to
4390 run as generic HVM guest with no PV drivers.
4391
4392 xirc2ps_cs= [NET,PCMCIA]
4393 Format:
4394 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]