| 1 | # SPDX-License-Identifier: GPL-2.0-only |
| 2 | menuconfig DAX |
| 3 | tristate "DAX: direct access to differentiated memory" |
| 4 | default m if NVDIMM_DAX |
| 5 | |
| 6 | if DAX |
| 7 | |
| 8 | config 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 | |
| 19 | config 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 | |
| 30 | config 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_MEMBLKS |
| 34 | default DEV_DAX |
| 35 | depends on CXL_ACPI || !CXL_ACPI |
| 36 | depends on CXL_PCI || !CXL_PCI |
| 37 | depends on CXL_BUS || !CXL_BUS |
| 38 | help |
| 39 | EFI 2.8 platforms, and others, may advertise 'specific purpose' |
| 40 | memory. For example, a high bandwidth memory pool. The |
| 41 | indication from platform firmware is meant to reserve the |
| 42 | memory from typical usage by default. This driver creates |
| 43 | device-dax instances for these memory ranges, and that also |
| 44 | enables the possibility to assign them to the DEV_DAX_KMEM |
| 45 | driver to override the reservation and add them to kernel |
| 46 | "System RAM" pool. |
| 47 | |
| 48 | Say M if unsure. |
| 49 | |
| 50 | config DEV_DAX_CXL |
| 51 | tristate "CXL DAX: direct access to CXL RAM regions" |
| 52 | depends on CXL_BUS && CXL_REGION && DEV_DAX |
| 53 | default CXL_REGION && DEV_DAX |
| 54 | depends on DEV_DAX_HMEM || !DEV_DAX_HMEM |
| 55 | help |
| 56 | CXL RAM regions are either mapped by platform-firmware |
| 57 | and published in the initial system-memory map as "System RAM", mapped |
| 58 | by platform-firmware as "Soft Reserved", or dynamically provisioned |
| 59 | after boot by the CXL driver. In the latter two cases a device-dax |
| 60 | instance is created to access that unmapped-by-default address range. |
| 61 | Per usual it can remain as dedicated access via a device interface, or |
| 62 | converted to "System RAM" via the dax_kmem facility. |
| 63 | |
| 64 | config DEV_DAX_HMEM_DEVICES |
| 65 | depends on DEV_DAX_HMEM && DAX |
| 66 | def_bool y |
| 67 | |
| 68 | config DEV_DAX_FSDEV |
| 69 | tristate |
| 70 | depends on DEV_DAX && FS_DAX |
| 71 | default DEV_DAX |
| 72 | |
| 73 | config DEV_DAX_KMEM |
| 74 | tristate "KMEM DAX: map dax-devices as System-RAM" |
| 75 | default DEV_DAX |
| 76 | depends on DEV_DAX |
| 77 | depends on MEMORY_HOTPLUG # for add_memory() and friends |
| 78 | help |
| 79 | Support access to persistent, or other performance |
| 80 | differentiated memory as if it were System RAM. This allows |
| 81 | easier use of persistent memory by unmodified applications, or |
| 82 | adds core kernel memory services to heterogeneous memory types |
| 83 | (HMEM) marked "reserved" by platform firmware. |
| 84 | |
| 85 | To use this feature, a DAX device must be unbound from the |
| 86 | device_dax driver and bound to this kmem driver on each boot. |
| 87 | |
| 88 | Say N if unsure. |
| 89 | |
| 90 | endif |