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# SPDX-License-Identifier: GPL-2.0-only
menuconfig DAX
tristate "DAX: direct access to differentiated memory"
default m if NVDIMM_DAX
if DAX
config DEV_DAX
tristate "Device DAX: direct access mapping device"
depends on TRANSPARENT_HUGEPAGE
help
Support raw access to differentiated (persistence, bandwidth,
latency...) memory via an mmap(2) capable character
device. Platform firmware or a device driver may identify a
platform memory resource that is differentiated from the
baseline memory pool. Mappings of a /dev/daxX.Y device impose
restrictions that make the mapping behavior deterministic.
config DEV_DAX_PMEM
tristate "PMEM DAX: direct access to persistent memory"
depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX
default DEV_DAX
help
Support raw access to persistent memory. Note that this
driver consumes memory ranges allocated and exported by the
libnvdimm sub-system.
Say M if unsure
config DEV_DAX_HMEM
tristate "HMEM DAX: direct access to 'specific purpose' memory"
depends on EFI_SOFT_RESERVE
select NUMA_KEEP_MEMINFO if (NUMA && X86)
default DEV_DAX
help
EFI 2.8 platforms, and others, may advertise 'specific purpose'
memory. For example, a high bandwidth memory pool. The
indication from platform firmware is meant to reserve the
memory from typical usage by default. This driver creates
device-dax instances for these memory ranges, and that also
enables the possibility to assign them to the DEV_DAX_KMEM
driver to override the reservation and add them to kernel
"System RAM" pool.
Say M if unsure.
config DEV_DAX_CXL
tristate "CXL DAX: direct access to CXL RAM regions"
depends on CXL_BUS && CXL_REGION && DEV_DAX
default CXL_REGION && DEV_DAX
help
CXL RAM regions are either mapped by platform-firmware
and published in the initial system-memory map as "System RAM", mapped
by platform-firmware as "Soft Reserved", or dynamically provisioned
after boot by the CXL driver. In the latter two cases a device-dax
instance is created to access that unmapped-by-default address range.
Per usual it can remain as dedicated access via a device interface, or
converted to "System RAM" via the dax_kmem facility.
config DEV_DAX_HMEM_DEVICES
depends on DEV_DAX_HMEM && DAX
def_bool y
config DEV_DAX_KMEM
tristate "KMEM DAX: map dax-devices as System-RAM"
default DEV_DAX
depends on DEV_DAX
depends on MEMORY_HOTPLUG # for add_memory() and friends
help
Support access to persistent, or other performance
differentiated memory as if it were System RAM. This allows
easier use of persistent memory by unmodified applications, or
adds core kernel memory services to heterogeneous memory types
(HMEM) marked "reserved" by platform firmware.
To use this feature, a DAX device must be unbound from the
device_dax driver and bound to this kmem driver on each boot.
Say N if unsure.
endif
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