Re: [PATCH v13 3/4] cxl/core: Add CXL EINJ debugfs files

Ben Cheatham
2024-02-21T20:27:43Z

On 2/21/24 11:48 AM, Dan Williams wrote:
> Ben Cheatham wrote:
>> Export CXL helper functions in the einj_cxl module for getting/injecting
>> available CXL protocol error types to sysfs under kernel/debug/cxl.
>>
>> The kernel/debug/cxl/einj_types file will print the available CXL
>> protocol errors in the same format as the available_error_types
>> file provided by the einj_cxl module. The
>> kernel/debug/cxl/$dport_dev/einj_inject is functionally the same as the
>> error_type and error_inject files provided by the EINJ module, i.e.:
>> writing an error type into $dport_dev/einj_inject will inject said error
>> type into the CXL dport represented by $dport_dev.
>>
>> Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
>> ---
>> Documentation/ABI/testing/debugfs-cxl | 30 ++++++++++++++++++++
>> drivers/cxl/Kconfig | 1 +
>> drivers/cxl/core/port.c | 41 +++++++++++++++++++++++++++
>> 3 files changed, 72 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/debugfs-cxl b/Documentation/ABI/testing/debugfs-cxl
>> index fe61d372e3fa..4c0f62f881ca 100644
>> --- a/Documentation/ABI/testing/debugfs-cxl
>> +++ b/Documentation/ABI/testing/debugfs-cxl
>> @@ -33,3 +33,33 @@ Description:
>> device cannot clear poison from the address, -ENXIO is returned.
>> The clear_poison attribute is only visible for devices
>> supporting the capability.
>> +
>> +What: /sys/kernel/debug/cxl/einj_types
>> +Date: January, 2024
>> +KernelVersion: v6.9
>> +Contact: linux-cxl@vger.kernel.org
>> +Description:
>> + (RO) Prints the CXL protocol error types made available by
>> + the platform in the format "0x<error number> <error type>".
>> + The possible error types are (as of ACPI v6.5):
>> + 0x1000 CXL.cache Protocol Correctable
>> + 0x2000 CXL.cache Protocol Uncorrectable non-fatal
>> + 0x4000 CXL.cache Protocol Uncorrectable fatal
>> + 0x8000 CXL.mem Protocol Correctable
>> + 0x10000 CXL.mem Protocol Uncorrectable non-fatal
>> + 0x20000 CXL.mem Protocol Uncorrectable fatal
>> +
>> + The <error number> can be written to einj_inject to inject
>> + <error type> into a chosen dport.
>> +
>> +What: /sys/kernel/debug/cxl/$dport_dev/einj_inject
>> +Date: January, 2024
>> +KernelVersion: v6.9
>> +Contact: linux-cxl@vger.kernel.org
>> +Description:
>> + (WO) Writing an integer to this file injects the corresponding
>> + CXL protocol error into $dport_dev ($dport_dev will be a device
>> + name from /sys/bus/pci/devices). The integer to type mapping for
>> + injection can be found by reading from einj_types. If the dport
>> + was enumerated in RCH mode, a CXL 1.1 error is injected, otherwise
>> + a CXL 2.0 error is injected.
>> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
>> index 67998dbd1d46..c86ae4c65c03 100644
>> --- a/drivers/cxl/Kconfig
>> +++ b/drivers/cxl/Kconfig
>> @@ -2,6 +2,7 @@
>> menuconfig CXL_BUS
>> tristate "CXL (Compute Express Link) Devices Support"
>> depends on PCI
>> + depends on ACPI_APEI_EINJ_CXL || !ACPI_APEI_EINJ_CXL
>
> This statement is always true "x || !x"

Yeah, I lifted this from the Kconfig documentation (https://www.kernel.org/doc/html/next/kbuild/kconfig-language.html#kconfig-hints).
It allows CXL_BUS to built if ACPI_APEI_EINJ_CXL=n, but restricts CXL_BUS >= ACPI_APEI_EINJ_CXL otherwise.
Now that I think about it, it seems like this just flipped the dependency I had in v12 the other way.

>
> I mentioned in the other patch that ACPI_APEI_EINJ_CXL needs to have a
> dependency on CXL_BUS.

Yep I agree, I was just having issues and was able to get it working this way.
I'll change this back to what it was.

Thanks,
Ben