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Platform firmware like EFI/ACPI may publish "hmem" platform devices. Such a device is a performance differentiated memory range likely reserved for an application specific use case. The driver gives access to 100% of the capacity via a device-dax mmap instance by default. However, if over-subscription and other kernel memory management is desired the resulting dax device can be assigned to the core-mm via the kmem driver. This consumes "hmem" devices the producer of "hmem" devices is saved for a follow-on patch so that it can reference the new CONFIG_DEV_DAX_HMEM symbol to gate performing the enumeration work. Reported-by: kbuild test robot <lkp@intel.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
78 lines
2.5 KiB
Plaintext
78 lines
2.5 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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config DAX_DRIVER
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select DAX
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bool
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menuconfig DAX
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tristate "DAX: direct access to differentiated memory"
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select SRCU
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default m if NVDIMM_DAX
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if DAX
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config DEV_DAX
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tristate "Device DAX: direct access mapping device"
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depends on TRANSPARENT_HUGEPAGE
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help
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Support raw access to differentiated (persistence, bandwidth,
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latency...) memory via an mmap(2) capable character
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device. Platform firmware or a device driver may identify a
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platform memory resource that is differentiated from the
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baseline memory pool. Mappings of a /dev/daxX.Y device impose
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restrictions that make the mapping behavior deterministic.
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config DEV_DAX_PMEM
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tristate "PMEM DAX: direct access to persistent memory"
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depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX
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default DEV_DAX
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help
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Support raw access to persistent memory. Note that this
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driver consumes memory ranges allocated and exported by the
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libnvdimm sub-system.
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Say M if unsure
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config DEV_DAX_HMEM
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tristate "HMEM DAX: direct access to 'specific purpose' memory"
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depends on EFI_SOFT_RESERVE
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default DEV_DAX
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help
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EFI 2.8 platforms, and others, may advertise 'specific purpose'
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memory. For example, a high bandwidth memory pool. The
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indication from platform firmware is meant to reserve the
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memory from typical usage by default. This driver creates
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device-dax instances for these memory ranges, and that also
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enables the possibility to assign them to the DEV_DAX_KMEM
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driver to override the reservation and add them to kernel
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"System RAM" pool.
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Say M if unsure.
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config DEV_DAX_KMEM
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tristate "KMEM DAX: volatile-use of persistent memory"
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default DEV_DAX
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depends on DEV_DAX
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depends on MEMORY_HOTPLUG # for add_memory() and friends
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help
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Support access to persistent, or other performance
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differentiated memory as if it were System RAM. This allows
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easier use of persistent memory by unmodified applications, or
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adds core kernel memory services to heterogeneous memory types
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(HMEM) marked "reserved" by platform firmware.
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To use this feature, a DAX device must be unbound from the
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device_dax driver and bound to this kmem driver on each boot.
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Say N if unsure.
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config DEV_DAX_PMEM_COMPAT
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tristate "PMEM DAX: support the deprecated /sys/class/dax interface"
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depends on m && DEV_DAX_PMEM=m
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default DEV_DAX_PMEM
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help
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Older versions of the libdaxctl library expect to find all
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device-dax instances under /sys/class/dax. If libdaxctl in
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your distribution is older than v58 say M, otherwise say N.
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endif
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