1# SPDX-License-Identifier: GPL-2.0-only
 2menuconfig DAX
 3	tristate "DAX: direct access to differentiated memory"
 4	default m if NVDIMM_DAX
 5
 6if DAX
 7
 8config DEV_DAX
 9	tristate "Device DAX: direct access mapping device"
10	depends on TRANSPARENT_HUGEPAGE
11	help
12	  Support raw access to differentiated (persistence, bandwidth,
13	  latency...) memory via an mmap(2) capable character
14	  device.  Platform firmware or a device driver may identify a
15	  platform memory resource that is differentiated from the
16	  baseline memory pool.  Mappings of a /dev/daxX.Y device impose
17	  restrictions that make the mapping behavior deterministic.
18
19config DEV_DAX_PMEM
20	tristate "PMEM DAX: direct access to persistent memory"
21	depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX
22	default DEV_DAX
23	help
24	  Support raw access to persistent memory.  Note that this
25	  driver consumes memory ranges allocated and exported by the
26	  libnvdimm sub-system.
27
28	  Say M if unsure
29
30config DEV_DAX_HMEM
31	tristate "HMEM DAX: direct access to 'specific purpose' memory"
32	depends on EFI_SOFT_RESERVE
33	select NUMA_KEEP_MEMINFO if (NUMA && X86)
34	default DEV_DAX
35	help
36	  EFI 2.8 platforms, and others, may advertise 'specific purpose'
37	  memory. For example, a high bandwidth memory pool. The
38	  indication from platform firmware is meant to reserve the
39	  memory from typical usage by default. This driver creates
40	  device-dax instances for these memory ranges, and that also
41	  enables the possibility to assign them to the DEV_DAX_KMEM
42	  driver to override the reservation and add them to kernel
43	  "System RAM" pool.
44
45	  Say M if unsure.
46
47config DEV_DAX_CXL
48	tristate "CXL DAX: direct access to CXL RAM regions"
49	depends on CXL_BUS && CXL_REGION && DEV_DAX
50	default CXL_REGION && DEV_DAX
51	help
52	  CXL RAM regions are either mapped by platform-firmware
53	  and published in the initial system-memory map as "System RAM", mapped
54	  by platform-firmware as "Soft Reserved", or dynamically provisioned
55	  after boot by the CXL driver. In the latter two cases a device-dax
56	  instance is created to access that unmapped-by-default address range.
57	  Per usual it can remain as dedicated access via a device interface, or
58	  converted to "System RAM" via the dax_kmem facility.
59
60config DEV_DAX_HMEM_DEVICES
61	depends on DEV_DAX_HMEM && DAX
62	def_bool y
63
64config DEV_DAX_KMEM
65	tristate "KMEM DAX: map dax-devices as System-RAM"
66	default DEV_DAX
67	depends on DEV_DAX
68	depends on MEMORY_HOTPLUG # for add_memory() and friends
69	help
70	  Support access to persistent, or other performance
71	  differentiated memory as if it were System RAM. This allows
72	  easier use of persistent memory by unmodified applications, or
73	  adds core kernel memory services to heterogeneous memory types
74	  (HMEM) marked "reserved" by platform firmware.
75
76	  To use this feature, a DAX device must be unbound from the
77	  device_dax driver and bound to this kmem driver on each boot.
78
79	  Say N if unsure.
80
81endif