Re: [PATCH v5 7/7] Documentation: Add docs for inject/clear-error commands

[Alison Schofield <alison.schofield@intel.com>]

On Mon, Dec 15, 2025 at 03:36:30PM -0600, Ben Cheatham wrote:
> Add man pages for the 'cxl-inject-error' and 'cxl-clear-error' commands.
> These man pages show usage and examples for each of their use cases.
> 
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
> ---
>  Documentation/cxl/cxl-clear-error.txt  |  67 +++++++++++++
>  Documentation/cxl/cxl-inject-error.txt | 129 +++++++++++++++++++++++++
>  Documentation/cxl/meson.build          |   2 +
>  3 files changed, 198 insertions(+)
>  create mode 100644 Documentation/cxl/cxl-clear-error.txt
>  create mode 100644 Documentation/cxl/cxl-inject-error.txt

snip

> diff --git a/Documentation/cxl/cxl-inject-error.txt b/Documentation/cxl/cxl-inject-error.txt
> new file mode 100644
> index 0000000..e1bebd7
> --- /dev/null
> +++ b/Documentation/cxl/cxl-inject-error.txt
> @@ -0,0 +1,129 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +cxl-inject-error(1)
> +===================
> +
> +NAME
> +----
> +cxl-inject-error - Inject CXL errors into CXL devices
> +
> +SYNOPSIS
> +--------
> +[verse]
> +'cxl inject-error' <device name> [<options>]
> +
> +Inject an error into a CXL device. The type of errors supported depend on the
> +device specified. The types of devices supported are:
> +
> +"Downstream Ports":: A CXL RCH downstream port (dport) or a CXL VH root port.
> +Eligible CXL 2.0+ ports are dports of ports at depth 1 in the output of cxl-list.
> +Dports are specified by host name ("0000:0e:01.1").

How are users to find that dport host?

Is there a cxl list "show me the dports where i can inject protocol errors"
incantation that we can recommend here.

I ended up looking at /sys/kernel/debug/cxl/ to find the hosts.

Would another attribute added to those dports make sense, be possible?
like is done for the poison injectable memdevs?  ie 'protocol_injectable: true'


> +"memdevs":: A CXL memory device. Memory devices are specified by device name
> +("mem0"), device id ("0"), and/or host device name ("0000:35:00.0").
> +
> +There are two types of errors which can be injected: CXL protocol errors
> +and device poison.
> +
> +CXL protocol errors can only be used with downstream ports (as defined above).
> +Protocol errors follow the format of "<protocol>-<severity>". For example,
> +a "mem-fatal" error is a CXL.mem fatal protocol error. Protocol errors can be
> +found with the '-N' option of 'cxl-list' under a CXL bus object. For example:
> +
> +----
> +
> +# cxl list -NB
> +[
> +  {
> +	"bus":"root0",
> +	"provider":"ACPI.CXL",
> +	"injectable_protocol_errors":[
> +	  "mem-correctable",
> +	  "mem-fatal",
> +	]
> +  }
> +]
> +
> +----
> +
> +CXL protocol (CXL.cache/mem) error injection requires the platform to support
> +ACPI v6.5+ error injection (EINJ). In addition to platform support, the
> +CONFIG_ACPI_APEI_EINJ and CONFIG_ACPI_APEI_EINJ_CXL kernel configuration options
> +will need to be enabled. For more information, view the Linux kernel documentation
> +on EINJ.
> +
> +Device poison can only by used with CXL memory devices. A device physical address
> +(DPA) is required to do poison injection. DPAs range from 0 to the size of
> +device's memory, which can be found using 'cxl-list'. An example injection:
> +
> +----
> +
> +# cxl inject-error mem0 -t poison -a 0x1000
> +poison injected at mem0:0x1000
> +# cxl list -m mem0 -u --media-errors
> +{
> +  "memdev":"mem0",
> +  "ram_size":"256.00 MiB (268.44 MB)",
> +  "serial":"0",
> +  "host":"0000:0d:00.0",
> +  "firmware_version":"BWFW VERSION 00",
> +  "media_errors":[
> +    {
> +      "offset":"0x1000",
> +      "length":64,
> +      "source":"Injected"
> +    }
> +  ]
> +}
> +
> +----
> +
> +Not all devices support poison injection. To see if a device supports poison injection
> +through debugfs, use 'cxl-list' with the '-N' option and look for the "poison-injectable"
> +attribute under the device. Example:
> +
> +----
> +
> +# cxl list -Nu -m mem0
> +{
> +  "memdev":"mem0",
> +  "ram_size":"256.00 MiB (268.44 MB)",
> +  "serial":"0",
> +  "host":"0000:0d:00.0",
> +  "firmware_version":"BWFW VERSION 00",
> +  "poison_injectable":true
> +}
> +
> +----
> +
> +This command depends on the kernel debug filesystem (debugfs) to do CXL protocol
> +error and device poison injection.
> +
> +OPTIONS
> +-------
> +-a::
> +--address::
> +	Device physical address (DPA) to use for poison injection. Address can
> +	be specified in hex or decimal. Required for poison injection.
> +
> +-t::
> +--type::
> +	Type of error to inject into <device name>. The type of error is restricted
> +	by device type. The following shows the possible types under their associated
> +	device type(s):
> +----
> +
> +Downstream Ports: ::
> +	cache-correctable, cache-uncorrectable, cache-fatal, mem-correctable,
> +	mem-fatal
> +
> +Memdevs: ::
> +	poison
> +
> +----
> +
> +--debug::
> +	Enable debug output
> +
> +SEE ALSO
> +--------
> +linkcxl:cxl-list[1]
> diff --git a/Documentation/cxl/meson.build b/Documentation/cxl/meson.build
> index 8085c1c..0b75eed 100644
> --- a/Documentation/cxl/meson.build
> +++ b/Documentation/cxl/meson.build
> @@ -50,6 +50,8 @@ cxl_manpages = [
>    'cxl-update-firmware.txt',
>    'cxl-set-alert-config.txt',
>    'cxl-wait-sanitize.txt',
> +  'cxl-inject-error.txt',
> +  'cxl-clear-error.txt',
>  ]
>  
>  foreach man : cxl_manpages
> -- 
> 2.52.0
>