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The CXL memory device send interface will have a number of supported commands. The raw command is not such a command. Raw commands allow userspace to send a specified opcode to the underlying hardware and bypass all driver checks on the command. The primary use for this command is to [begrudgingly] allow undocumented vendor specific hardware commands. While not the main motivation, it also allows prototyping new hardware commands without a driver patch and rebuild. While this all sounds very powerful it comes with a couple of caveats: 1. Bug reports using raw commands will not get the same level of attention as bug reports using supported commands (via taint). 2. Supported commands will be rejected by the RAW command. With this comes new debugfs knob to allow full access to your toes with your weapon of choice. Signed-off-by: Ben Widawsky <ben.widawsky@intel.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2) Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Cc: Ariel Sibley <Ariel.Sibley@microchip.com> Link: https://lore.kernel.org/r/20210217040958.1354670-6-ben.widawsky@intel.com Signed-off-by: Dan Williams <dan.j.williams@intel.com>
54 lines
2.2 KiB
Plaintext
54 lines
2.2 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0-only
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menuconfig CXL_BUS
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tristate "CXL (Compute Express Link) Devices Support"
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depends on PCI
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help
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CXL is a bus that is electrically compatible with PCI Express, but
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layers three protocols on that signalling (CXL.io, CXL.cache, and
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CXL.mem). The CXL.cache protocol allows devices to hold cachelines
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locally, the CXL.mem protocol allows devices to be fully coherent
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memory targets, the CXL.io protocol is equivalent to PCI Express.
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Say 'y' to enable support for the configuration and management of
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devices supporting these protocols.
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if CXL_BUS
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config CXL_MEM
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tristate "CXL.mem: Memory Devices"
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help
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The CXL.mem protocol allows a device to act as a provider of
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"System RAM" and/or "Persistent Memory" that is fully coherent
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as if the memory was attached to the typical CPU memory
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controller.
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Say 'y/m' to enable a driver (named "cxl_mem.ko" when built as
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a module) that will attach to CXL.mem devices for
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configuration, provisioning, and health monitoring. This
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driver is required for dynamic provisioning of CXL.mem
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attached memory which is a prerequisite for persistent memory
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support. Typically volatile memory is mapped by platform
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firmware and included in the platform memory map, but in some
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cases the OS is responsible for mapping that memory. See
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Chapter 2.3 Type 3 CXL Device in the CXL 2.0 specification.
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If unsure say 'm'.
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config CXL_MEM_RAW_COMMANDS
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bool "RAW Command Interface for Memory Devices"
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depends on CXL_MEM
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help
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Enable CXL RAW command interface.
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The CXL driver ioctl interface may assign a kernel ioctl command
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number for each specification defined opcode. At any given point in
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time the number of opcodes that the specification defines and a device
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may implement may exceed the kernel's set of associated ioctl function
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numbers. The mismatch is either by omission, specification is too new,
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or by design. When prototyping new hardware, or developing / debugging
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the driver it is useful to be able to submit any possible command to
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the hardware, even commands that may crash the kernel due to their
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potential impact to memory currently in use by the kernel.
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If developing CXL hardware or the driver say Y, otherwise say N.
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endif
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