xref: /linux/drivers/cxl/Kconfig (revision cbbd05d036e91b9dd976af4382f6c8d91b69b38a)

# SPDX-License-Identifier: GPL-2.0-only
menuconfig CXL_BUS
	tristate "CXL (Compute Express Link) Devices Support"
	depends on PCI
	select PCI_DOE
	help
	  CXL is a bus that is electrically compatible with PCI Express, but
	  layers three protocols on that signalling (CXL.io, CXL.cache, and
	  CXL.mem). The CXL.cache protocol allows devices to hold cachelines
	  locally, the CXL.mem protocol allows devices to be fully coherent
	  memory targets, the CXL.io protocol is equivalent to PCI Express.
	  Say 'y' to enable support for the configuration and management of
	  devices supporting these protocols.

if CXL_BUS

config CXL_PCI
	tristate "PCI manageability"
	default CXL_BUS
	help
	  The CXL specification defines a "CXL memory device" sub-class in the
	  PCI "memory controller" base class of devices. Device's identified by
	  this class code provide support for volatile and / or persistent
	  memory to be mapped into the system address map (Host-managed Device
	  Memory (HDM)).

	  Say 'y/m' to enable a driver that will attach to CXL memory expander
	  devices enumerated by the memory device class code for configuration
	  and management primarily via the mailbox interface. See Chapter 2.3
	  Type 3 CXL Device in the CXL 2.0 specification for more details.

	  If unsure say 'm'.

config CXL_MEM_RAW_COMMANDS
	bool "RAW Command Interface for Memory Devices"
	depends on CXL_PCI
	help
	  Enable CXL RAW command interface.

	  The CXL driver ioctl interface may assign a kernel ioctl command
	  number for each specification defined opcode. At any given point in
	  time the number of opcodes that the specification defines and a device
	  may implement may exceed the kernel's set of associated ioctl function
	  numbers. The mismatch is either by omission, specification is too new,
	  or by design. When prototyping new hardware, or developing / debugging
	  the driver it is useful to be able to submit any possible command to
	  the hardware, even commands that may crash the kernel due to their
	  potential impact to memory currently in use by the kernel.

	  If developing CXL hardware or the driver say Y, otherwise say N.

config CXL_ACPI
	tristate "CXL ACPI: Platform Support"
	depends on ACPI
	default CXL_BUS
	select ACPI_TABLE_LIB
	help
	  Enable support for host managed device memory (HDM) resources
	  published by a platform's ACPI CXL memory layout description.  See
	  Chapter 9.14.1 CXL Early Discovery Table (CEDT) in the CXL 2.0
	  specification, and CXL Fixed Memory Window Structures (CEDT.CFMWS)
	  (https://www.computeexpresslink.org/spec-landing). The CXL core
	  consumes these resource to publish the root of a cxl_port decode
	  hierarchy to map regions that represent System RAM, or Persistent
	  Memory regions to be managed by LIBNVDIMM.

	  If unsure say 'm'.

config CXL_PMEM
	tristate "CXL PMEM: Persistent Memory Support"
	depends on LIBNVDIMM
	default CXL_BUS
	help
	  In addition to typical memory resources a platform may also advertise
	  support for persistent memory attached via CXL. This support is
	  managed via a bridge driver from CXL to the LIBNVDIMM system
	  subsystem. Say 'y/m' to enable support for enumerating and
	  provisioning the persistent memory capacity of CXL memory expanders.

	  If unsure say 'm'.

config CXL_MEM
	tristate "CXL: Memory Expansion"
	depends on CXL_PCI
	default CXL_BUS
	help
	  The CXL.mem protocol allows a device to act as a provider of "System
	  RAM" and/or "Persistent Memory" that is fully coherent as if the
	  memory were attached to the typical CPU memory controller. This is
	  known as HDM "Host-managed Device Memory".

	  Say 'y/m' to enable a driver that will attach to CXL.mem devices for
	  memory expansion and control of HDM. See Chapter 9.13 in the CXL 2.0
	  specification for a detailed description of HDM.

	  If unsure say 'm'.

config CXL_PORT
	default CXL_BUS
	tristate

config CXL_SUSPEND
	def_bool y
	depends on SUSPEND && CXL_MEM

config CXL_REGION
	bool
	default CXL_BUS
	# For MAX_PHYSMEM_BITS
	depends on SPARSEMEM
	select MEMREGION
	select GET_FREE_REGION

config CXL_REGION_INVALIDATION_TEST
	bool "CXL: Region Cache Management Bypass (TEST)"
	depends on CXL_REGION
	help
	  CXL Region management and security operations potentially invalidate
	  the content of CPU caches without notifying those caches to
	  invalidate the affected cachelines. The CXL Region driver attempts
	  to invalidate caches when those events occur.  If that invalidation
	  fails the region will fail to enable.  Reasons for cache
	  invalidation failure are due to the CPU not providing a cache
	  invalidation mechanism. For example usage of wbinvd is restricted to
	  bare metal x86. However, for testing purposes toggling this option
	  can disable that data integrity safety and proceed with enabling
	  regions when there might be conflicting contents in the CPU cache.

	  If unsure, or if this kernel is meant for production environments,
	  say N.

endif