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_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 50config 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 64config DEV_DAX_HMEM_DEVICES 65 depends on DEV_DAX_HMEM && DAX 66 def_bool y 67 68config DEV_DAX_KMEM 69 tristate "KMEM DAX: map dax-devices as System-RAM" 70 default DEV_DAX 71 depends on DEV_DAX 72 depends on MEMORY_HOTPLUG # for add_memory() and friends 73 help 74 Support access to persistent, or other performance 75 differentiated memory as if it were System RAM. This allows 76 easier use of persistent memory by unmodified applications, or 77 adds core kernel memory services to heterogeneous memory types 78 (HMEM) marked "reserved" by platform firmware. 79 80 To use this feature, a DAX device must be unbound from the 81 device_dax driver and bound to this kmem driver on each boot. 82 83 Say N if unsure. 84 85endif 86