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1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * Clocksource driver for the synthetic counter and timers
5 * provided by the Hyper-V hypervisor to guest VMs, as described
6 * in the Hyper-V Top Level Functional Spec (TLFS). This driver
7 * is instruction set architecture independent.
8 *
9 * Copyright (C) 2019, Microsoft, Inc.
10 *
11 * Author: Michael Kelley <mikelley@microsoft.com>
12 */
13
14#include <linux/percpu.h>
15#include <linux/cpumask.h>
16#include <linux/clockchips.h>
17#include <linux/clocksource.h>
18#include <linux/sched_clock.h>
19#include <linux/mm.h>
20#include <linux/cpuhotplug.h>
21#include <linux/interrupt.h>
22#include <linux/irq.h>
23#include <linux/acpi.h>
24#include <linux/hyperv.h>
25#include <clocksource/hyperv_timer.h>
26#include <asm/hyperv-tlfs.h>
27#include <asm/mshyperv.h>
28
29static struct clock_event_device __percpu *hv_clock_event;
30/* Note: offset can hold negative values after hibernation. */
31static u64 hv_sched_clock_offset __read_mostly;
32
33/*
34 * If false, we're using the old mechanism for stimer0 interrupts
35 * where it sends a VMbus message when it expires. The old
36 * mechanism is used when running on older versions of Hyper-V
37 * that don't support Direct Mode. While Hyper-V provides
38 * four stimer's per CPU, Linux uses only stimer0.
39 *
40 * Because Direct Mode does not require processing a VMbus
41 * message, stimer interrupts can be enabled earlier in the
42 * process of booting a CPU, and consistent with when timer
43 * interrupts are enabled for other clocksource drivers.
44 * However, for legacy versions of Hyper-V when Direct Mode
45 * is not enabled, setting up stimer interrupts must be
46 * delayed until VMbus is initialized and can process the
47 * interrupt message.
48 */
49static bool direct_mode_enabled;
50
51static int stimer0_irq = -1;
52static int stimer0_message_sint;
53static __maybe_unused DEFINE_PER_CPU(long, stimer0_evt);
54
55/*
56 * Common code for stimer0 interrupts coming via Direct Mode or
57 * as a VMbus message.
58 */
59void hv_stimer0_isr(void)
60{
61 struct clock_event_device *ce;
62
63 ce = this_cpu_ptr(hv_clock_event);
64 ce->event_handler(ce);
65}
66EXPORT_SYMBOL_GPL(hv_stimer0_isr);
67
68/*
69 * stimer0 interrupt handler for architectures that support
70 * per-cpu interrupts, which also implies Direct Mode.
71 */
72static irqreturn_t __maybe_unused hv_stimer0_percpu_isr(int irq, void *dev_id)
73{
74 hv_stimer0_isr();
75 return IRQ_HANDLED;
76}
77
78static int hv_ce_set_next_event(unsigned long delta,
79 struct clock_event_device *evt)
80{
81 u64 current_tick;
82
83 current_tick = hv_read_reference_counter();
84 current_tick += delta;
85 hv_set_msr(HV_MSR_STIMER0_COUNT, current_tick);
86 return 0;
87}
88
89static int hv_ce_shutdown(struct clock_event_device *evt)
90{
91 hv_set_msr(HV_MSR_STIMER0_COUNT, 0);
92 hv_set_msr(HV_MSR_STIMER0_CONFIG, 0);
93 if (direct_mode_enabled && stimer0_irq >= 0)
94 disable_percpu_irq(stimer0_irq);
95
96 return 0;
97}
98
99static int hv_ce_set_oneshot(struct clock_event_device *evt)
100{
101 union hv_stimer_config timer_cfg;
102
103 timer_cfg.as_uint64 = 0;
104 timer_cfg.enable = 1;
105 timer_cfg.auto_enable = 1;
106 if (direct_mode_enabled) {
107 /*
108 * When it expires, the timer will directly interrupt
109 * on the specified hardware vector/IRQ.
110 */
111 timer_cfg.direct_mode = 1;
112 timer_cfg.apic_vector = HYPERV_STIMER0_VECTOR;
113 if (stimer0_irq >= 0)
114 enable_percpu_irq(stimer0_irq, IRQ_TYPE_NONE);
115 } else {
116 /*
117 * When it expires, the timer will generate a VMbus message,
118 * to be handled by the normal VMbus interrupt handler.
119 */
120 timer_cfg.direct_mode = 0;
121 timer_cfg.sintx = stimer0_message_sint;
122 }
123 hv_set_msr(HV_MSR_STIMER0_CONFIG, timer_cfg.as_uint64);
124 return 0;
125}
126
127/*
128 * hv_stimer_init - Per-cpu initialization of the clockevent
129 */
130static int hv_stimer_init(unsigned int cpu)
131{
132 struct clock_event_device *ce;
133
134 if (!hv_clock_event)
135 return 0;
136
137 ce = per_cpu_ptr(hv_clock_event, cpu);
138 ce->name = "Hyper-V clockevent";
139 ce->features = CLOCK_EVT_FEAT_ONESHOT;
140 ce->cpumask = cpumask_of(cpu);
141
142 /*
143 * Lower the rating of the Hyper-V timer in a TDX VM without paravisor,
144 * so the local APIC timer (lapic_clockevent) is the default timer in
145 * such a VM. The Hyper-V timer is not preferred in such a VM because
146 * it depends on the slow VM Reference Counter MSR (the Hyper-V TSC
147 * page is not enbled in such a VM because the VM uses Invariant TSC
148 * as a better clocksource and it's challenging to mark the Hyper-V
149 * TSC page shared in very early boot).
150 */
151 if (!ms_hyperv.paravisor_present && hv_isolation_type_tdx())
152 ce->rating = 90;
153 else
154 ce->rating = 1000;
155
156 ce->set_state_shutdown = hv_ce_shutdown;
157 ce->set_state_oneshot = hv_ce_set_oneshot;
158 ce->set_next_event = hv_ce_set_next_event;
159
160 clockevents_config_and_register(ce,
161 HV_CLOCK_HZ,
162 HV_MIN_DELTA_TICKS,
163 HV_MAX_MAX_DELTA_TICKS);
164 return 0;
165}
166
167/*
168 * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
169 */
170int hv_stimer_cleanup(unsigned int cpu)
171{
172 struct clock_event_device *ce;
173
174 if (!hv_clock_event)
175 return 0;
176
177 /*
178 * In the legacy case where Direct Mode is not enabled
179 * (which can only be on x86/64), stimer cleanup happens
180 * relatively early in the CPU offlining process. We
181 * must unbind the stimer-based clockevent device so
182 * that the LAPIC timer can take over until clockevents
183 * are no longer needed in the offlining process. Note
184 * that clockevents_unbind_device() eventually calls
185 * hv_ce_shutdown().
186 *
187 * The unbind should not be done when Direct Mode is
188 * enabled because we may be on an architecture where
189 * there are no other clockevent devices to fallback to.
190 */
191 ce = per_cpu_ptr(hv_clock_event, cpu);
192 if (direct_mode_enabled)
193 hv_ce_shutdown(ce);
194 else
195 clockevents_unbind_device(ce, cpu);
196
197 return 0;
198}
199EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
200
201/*
202 * These placeholders are overridden by arch specific code on
203 * architectures that need special setup of the stimer0 IRQ because
204 * they don't support per-cpu IRQs (such as x86/x64).
205 */
206void __weak hv_setup_stimer0_handler(void (*handler)(void))
207{
208};
209
210void __weak hv_remove_stimer0_handler(void)
211{
212};
213
214#ifdef CONFIG_ACPI
215/* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */
216static int hv_setup_stimer0_irq(void)
217{
218 int ret;
219
220 ret = acpi_register_gsi(NULL, HYPERV_STIMER0_VECTOR,
221 ACPI_EDGE_SENSITIVE, ACPI_ACTIVE_HIGH);
222 if (ret < 0) {
223 pr_err("Can't register Hyper-V stimer0 GSI. Error %d", ret);
224 return ret;
225 }
226 stimer0_irq = ret;
227
228 ret = request_percpu_irq(stimer0_irq, hv_stimer0_percpu_isr,
229 "Hyper-V stimer0", &stimer0_evt);
230 if (ret) {
231 pr_err("Can't request Hyper-V stimer0 IRQ %d. Error %d",
232 stimer0_irq, ret);
233 acpi_unregister_gsi(stimer0_irq);
234 stimer0_irq = -1;
235 }
236 return ret;
237}
238
239static void hv_remove_stimer0_irq(void)
240{
241 if (stimer0_irq == -1) {
242 hv_remove_stimer0_handler();
243 } else {
244 free_percpu_irq(stimer0_irq, &stimer0_evt);
245 acpi_unregister_gsi(stimer0_irq);
246 stimer0_irq = -1;
247 }
248}
249#else
250static int hv_setup_stimer0_irq(void)
251{
252 return 0;
253}
254
255static void hv_remove_stimer0_irq(void)
256{
257}
258#endif
259
260/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
261int hv_stimer_alloc(bool have_percpu_irqs)
262{
263 int ret;
264
265 /*
266 * Synthetic timers are always available except on old versions of
267 * Hyper-V on x86. In that case, return as error as Linux will use a
268 * clockevent based on emulated LAPIC timer hardware.
269 */
270 if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
271 return -EINVAL;
272
273 hv_clock_event = alloc_percpu(struct clock_event_device);
274 if (!hv_clock_event)
275 return -ENOMEM;
276
277 direct_mode_enabled = ms_hyperv.misc_features &
278 HV_STIMER_DIRECT_MODE_AVAILABLE;
279
280 /*
281 * If Direct Mode isn't enabled, the remainder of the initialization
282 * is done later by hv_stimer_legacy_init()
283 */
284 if (!direct_mode_enabled)
285 return 0;
286
287 if (have_percpu_irqs) {
288 ret = hv_setup_stimer0_irq();
289 if (ret)
290 goto free_clock_event;
291 } else {
292 hv_setup_stimer0_handler(hv_stimer0_isr);
293 }
294
295 /*
296 * Since we are in Direct Mode, stimer initialization
297 * can be done now with a CPUHP value in the same range
298 * as other clockevent devices.
299 */
300 ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
301 "clockevents/hyperv/stimer:starting",
302 hv_stimer_init, hv_stimer_cleanup);
303 if (ret < 0) {
304 hv_remove_stimer0_irq();
305 goto free_clock_event;
306 }
307 return ret;
308
309free_clock_event:
310 free_percpu(hv_clock_event);
311 hv_clock_event = NULL;
312 return ret;
313}
314EXPORT_SYMBOL_GPL(hv_stimer_alloc);
315
316/*
317 * hv_stimer_legacy_init -- Called from the VMbus driver to handle
318 * the case when Direct Mode is not enabled, and the stimer
319 * must be initialized late in the CPU onlining process.
320 *
321 */
322void hv_stimer_legacy_init(unsigned int cpu, int sint)
323{
324 if (direct_mode_enabled)
325 return;
326
327 /*
328 * This function gets called by each vCPU, so setting the
329 * global stimer_message_sint value each time is conceptually
330 * not ideal, but the value passed in is always the same and
331 * it avoids introducing yet another interface into this
332 * clocksource driver just to set the sint in the legacy case.
333 */
334 stimer0_message_sint = sint;
335 (void)hv_stimer_init(cpu);
336}
337EXPORT_SYMBOL_GPL(hv_stimer_legacy_init);
338
339/*
340 * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
341 * handle the case when Direct Mode is not enabled, and the
342 * stimer must be cleaned up early in the CPU offlining
343 * process.
344 */
345void hv_stimer_legacy_cleanup(unsigned int cpu)
346{
347 if (direct_mode_enabled)
348 return;
349 (void)hv_stimer_cleanup(cpu);
350}
351EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);
352
353/*
354 * Do a global cleanup of clockevents for the cases of kexec and
355 * vmbus exit
356 */
357void hv_stimer_global_cleanup(void)
358{
359 int cpu;
360
361 /*
362 * hv_stime_legacy_cleanup() will stop the stimer if Direct
363 * Mode is not enabled, and fallback to the LAPIC timer.
364 */
365 for_each_present_cpu(cpu) {
366 hv_stimer_legacy_cleanup(cpu);
367 }
368
369 if (!hv_clock_event)
370 return;
371
372 if (direct_mode_enabled) {
373 cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
374 hv_remove_stimer0_irq();
375 stimer0_irq = -1;
376 }
377 free_percpu(hv_clock_event);
378 hv_clock_event = NULL;
379
380}
381EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
382
383static __always_inline u64 read_hv_clock_msr(void)
384{
385 /*
386 * Read the partition counter to get the current tick count. This count
387 * is set to 0 when the partition is created and is incremented in 100
388 * nanosecond units.
389 *
390 * Use hv_raw_get_msr() because this function is used from
391 * noinstr. Notable; while HV_MSR_TIME_REF_COUNT is a synthetic
392 * register it doesn't need the GHCB path.
393 */
394 return hv_raw_get_msr(HV_MSR_TIME_REF_COUNT);
395}
396
397/*
398 * Code and definitions for the Hyper-V clocksources. Two
399 * clocksources are defined: one that reads the Hyper-V defined MSR, and
400 * the other that uses the TSC reference page feature as defined in the
401 * TLFS. The MSR version is for compatibility with old versions of
402 * Hyper-V and 32-bit x86. The TSC reference page version is preferred.
403 */
404
405static union {
406 struct ms_hyperv_tsc_page page;
407 u8 reserved[PAGE_SIZE];
408} tsc_pg __bss_decrypted __aligned(PAGE_SIZE);
409
410static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page;
411static unsigned long tsc_pfn;
412
413unsigned long hv_get_tsc_pfn(void)
414{
415 return tsc_pfn;
416}
417EXPORT_SYMBOL_GPL(hv_get_tsc_pfn);
418
419struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
420{
421 return tsc_page;
422}
423EXPORT_SYMBOL_GPL(hv_get_tsc_page);
424
425static __always_inline u64 read_hv_clock_tsc(void)
426{
427 u64 cur_tsc, time;
428
429 /*
430 * The Hyper-V Top-Level Function Spec (TLFS), section Timers,
431 * subsection Refererence Counter, guarantees that the TSC and MSR
432 * times are in sync and monotonic. Therefore we can fall back
433 * to the MSR in case the TSC page indicates unavailability.
434 */
435 if (!hv_read_tsc_page_tsc(tsc_page, &cur_tsc, &time))
436 time = read_hv_clock_msr();
437
438 return time;
439}
440
441static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
442{
443 return read_hv_clock_tsc();
444}
445
446static u64 noinstr read_hv_sched_clock_tsc(void)
447{
448 return (read_hv_clock_tsc() - hv_sched_clock_offset) *
449 (NSEC_PER_SEC / HV_CLOCK_HZ);
450}
451
452static void suspend_hv_clock_tsc(struct clocksource *arg)
453{
454 union hv_reference_tsc_msr tsc_msr;
455
456 /* Disable the TSC page */
457 tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC);
458 tsc_msr.enable = 0;
459 hv_set_msr(HV_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
460}
461
462
463static void resume_hv_clock_tsc(struct clocksource *arg)
464{
465 union hv_reference_tsc_msr tsc_msr;
466
467 /* Re-enable the TSC page */
468 tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC);
469 tsc_msr.enable = 1;
470 tsc_msr.pfn = tsc_pfn;
471 hv_set_msr(HV_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
472}
473
474/*
475 * Called during resume from hibernation, from overridden
476 * x86_platform.restore_sched_clock_state routine. This is to adjust offsets
477 * used to calculate time for hv tsc page based sched_clock, to account for
478 * time spent before hibernation.
479 */
480void hv_adj_sched_clock_offset(u64 offset)
481{
482 hv_sched_clock_offset -= offset;
483}
484
485#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK
486static int hv_cs_enable(struct clocksource *cs)
487{
488 vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK);
489 return 0;
490}
491#endif
492
493static struct clocksource hyperv_cs_tsc = {
494 .name = "hyperv_clocksource_tsc_page",
495 .rating = 500,
496 .read = read_hv_clock_tsc_cs,
497 .mask = CLOCKSOURCE_MASK(64),
498 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
499 .suspend= suspend_hv_clock_tsc,
500 .resume = resume_hv_clock_tsc,
501#ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK
502 .enable = hv_cs_enable,
503 .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK,
504#else
505 .vdso_clock_mode = VDSO_CLOCKMODE_NONE,
506#endif
507};
508
509static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
510{
511 return read_hv_clock_msr();
512}
513
514static struct clocksource hyperv_cs_msr = {
515 .name = "hyperv_clocksource_msr",
516 .rating = 495,
517 .read = read_hv_clock_msr_cs,
518 .mask = CLOCKSOURCE_MASK(64),
519 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
520};
521
522/*
523 * Reference to pv_ops must be inline so objtool
524 * detection of noinstr violations can work correctly.
525 */
526#ifdef CONFIG_GENERIC_SCHED_CLOCK
527static __always_inline void hv_setup_sched_clock(void *sched_clock)
528{
529 /*
530 * We're on an architecture with generic sched clock (not x86/x64).
531 * The Hyper-V sched clock read function returns nanoseconds, not
532 * the normal 100ns units of the Hyper-V synthetic clock.
533 */
534 sched_clock_register(sched_clock, 64, NSEC_PER_SEC);
535}
536#elif defined CONFIG_PARAVIRT
537static __always_inline void hv_setup_sched_clock(void *sched_clock)
538{
539 /* We're on x86/x64 *and* using PV ops */
540 paravirt_set_sched_clock(sched_clock);
541}
542#else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */
543static __always_inline void hv_setup_sched_clock(void *sched_clock) {}
544#endif /* CONFIG_GENERIC_SCHED_CLOCK */
545
546static void __init hv_init_tsc_clocksource(void)
547{
548 union hv_reference_tsc_msr tsc_msr;
549
550 /*
551 * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly
552 * handles frequency and offset changes due to live migration,
553 * pause/resume, and other VM management operations. So lower the
554 * Hyper-V Reference TSC rating, causing the generic TSC to be used.
555 * TSC_INVARIANT is not offered on ARM64, so the Hyper-V Reference
556 * TSC will be preferred over the virtualized ARM64 arch counter.
557 */
558 if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT) {
559 hyperv_cs_tsc.rating = 250;
560 hyperv_cs_msr.rating = 245;
561 }
562
563 if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
564 return;
565
566 hv_read_reference_counter = read_hv_clock_tsc;
567
568 /*
569 * TSC page mapping works differently in root compared to guest.
570 * - In guest partition the guest PFN has to be passed to the
571 * hypervisor.
572 * - In root partition it's other way around: it has to map the PFN
573 * provided by the hypervisor.
574 * But it can't be mapped right here as it's too early and MMU isn't
575 * ready yet. So, we only set the enable bit here and will remap the
576 * page later in hv_remap_tsc_clocksource().
577 *
578 * It worth mentioning, that TSC clocksource read function
579 * (read_hv_clock_tsc) has a MSR-based fallback mechanism, used when
580 * TSC page is zeroed (which is the case until the PFN is remapped) and
581 * thus TSC clocksource will work even without the real TSC page
582 * mapped.
583 */
584 tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC);
585 if (hv_root_partition)
586 tsc_pfn = tsc_msr.pfn;
587 else
588 tsc_pfn = HVPFN_DOWN(virt_to_phys(tsc_page));
589 tsc_msr.enable = 1;
590 tsc_msr.pfn = tsc_pfn;
591 hv_set_msr(HV_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
592
593 clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
594
595 /*
596 * If TSC is invariant, then let it stay as the sched clock since it
597 * will be faster than reading the TSC page. But if not invariant, use
598 * the TSC page so that live migrations across hosts with different
599 * frequencies is handled correctly.
600 */
601 if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) {
602 hv_sched_clock_offset = hv_read_reference_counter();
603 hv_setup_sched_clock(read_hv_sched_clock_tsc);
604 }
605}
606
607void __init hv_init_clocksource(void)
608{
609 /*
610 * Try to set up the TSC page clocksource, then the MSR clocksource.
611 * At least one of these will always be available except on very old
612 * versions of Hyper-V on x86. In that case we won't have a Hyper-V
613 * clocksource, but Linux will still run with a clocksource based
614 * on the emulated PIT or LAPIC timer.
615 *
616 * Never use the MSR clocksource as sched clock. It's too slow.
617 * Better to use the native sched clock as the fallback.
618 */
619 hv_init_tsc_clocksource();
620
621 if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE)
622 clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
623}
624
625void __init hv_remap_tsc_clocksource(void)
626{
627 if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
628 return;
629
630 if (!hv_root_partition) {
631 WARN(1, "%s: attempt to remap TSC page in guest partition\n",
632 __func__);
633 return;
634 }
635
636 tsc_page = memremap(tsc_pfn << HV_HYP_PAGE_SHIFT, sizeof(tsc_pg),
637 MEMREMAP_WB);
638 if (!tsc_page)
639 pr_err("Failed to remap Hyper-V TSC page.\n");
640}