1# SPDX-License-Identifier: GPL-2.0-only 2menuconfig DAX 3 tristate "DAX: direct access to differentiated memory" 4 select SRCU 5 default m if NVDIMM_DAX 6 7if DAX 8 9config DEV_DAX 10 tristate "Device DAX: direct access mapping device" 11 depends on TRANSPARENT_HUGEPAGE 12 help 13 Support raw access to differentiated (persistence, bandwidth, 14 latency...) memory via an mmap(2) capable character 15 device. Platform firmware or a device driver may identify a 16 platform memory resource that is differentiated from the 17 baseline memory pool. Mappings of a /dev/daxX.Y device impose 18 restrictions that make the mapping behavior deterministic. 19 20config DEV_DAX_PMEM 21 tristate "PMEM DAX: direct access to persistent memory" 22 depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX 23 default DEV_DAX 24 help 25 Support raw access to persistent memory. Note that this 26 driver consumes memory ranges allocated and exported by the 27 libnvdimm sub-system. 28 29 Say M if unsure 30 31config DEV_DAX_HMEM 32 tristate "HMEM DAX: direct access to 'specific purpose' memory" 33 depends on EFI_SOFT_RESERVE 34 select NUMA_KEEP_MEMINFO if (NUMA && X86) 35 default DEV_DAX 36 help 37 EFI 2.8 platforms, and others, may advertise 'specific purpose' 38 memory. For example, a high bandwidth memory pool. The 39 indication from platform firmware is meant to reserve the 40 memory from typical usage by default. This driver creates 41 device-dax instances for these memory ranges, and that also 42 enables the possibility to assign them to the DEV_DAX_KMEM 43 driver to override the reservation and add them to kernel 44 "System RAM" pool. 45 46 Say M if unsure. 47 48config DEV_DAX_CXL 49 tristate "CXL DAX: direct access to CXL RAM regions" 50 depends on CXL_REGION && DEV_DAX 51 default CXL_REGION && DEV_DAX 52 help 53 CXL RAM regions are either mapped by platform-firmware 54 and published in the initial system-memory map as "System RAM", mapped 55 by platform-firmware as "Soft Reserved", or dynamically provisioned 56 after boot by the CXL driver. In the latter two cases a device-dax 57 instance is created to access that unmapped-by-default address range. 58 Per usual it can remain as dedicated access via a device interface, or 59 converted to "System RAM" via the dax_kmem facility. 60 61config DEV_DAX_HMEM_DEVICES 62 depends on DEV_DAX_HMEM && DAX 63 def_bool y 64 65config DEV_DAX_KMEM 66 tristate "KMEM DAX: map dax-devices as System-RAM" 67 default DEV_DAX 68 depends on DEV_DAX 69 depends on MEMORY_HOTPLUG # for add_memory() and friends 70 help 71 Support access to persistent, or other performance 72 differentiated memory as if it were System RAM. This allows 73 easier use of persistent memory by unmodified applications, or 74 adds core kernel memory services to heterogeneous memory types 75 (HMEM) marked "reserved" by platform firmware. 76 77 To use this feature, a DAX device must be unbound from the 78 device_dax driver and bound to this kmem driver on each boot. 79 80 Say N if unsure. 81 82endif 83