Re: [PATCH v16 04/10] PCI/ERR: Introduce PCI_ERS_RESULT_PANIC

["Bowman, Terry" <terry.bowman@amd.com>]

On 3/29/2026 4:57 PM, Dan Williams wrote:
> Terry Bowman wrote:
>> The CXL driver's uncorrectable (UCE) protocol error handling will be updated
>> in the future. One required change is for the CXL error handlers to force a
>> system panic when a UCE is detected.
>
> Similar comment as the last patch "future" has no meaning and "required"> comes with no context.
> 

I'll update to remove future reference.

>> Introduce PCI_ERS_RESULT_PANIC as a 'enum pci_ers_result' type. This will
>> be used by CXL UCE fatal and non-fatal recovery in future patches. Update
>> PCIe recovery documentation with details of PCI_ERS_RESULT_PANIC.
>>
>> To clarify, PCI's merge_result() implemented in err.c is not to be changed.
>> merge_result() is not aware of PCI_ERS_RESULT_PANIC and will not return
>> PCI_ERS_RESULT_PANIC.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
>> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>> Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>
>> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
>>
>> ---
>>
>> Changes in v15 -> v16:
>> - None
>>
>> Changes in v14 -> v15:
>> - None
>>
>> Changes in v13 -> v14:
>> - Add review-by for Dan
>> - Update Title prefix (Bjorn)
>> - Removed merge_result. Only logging error for device reporting the
>>   error (Dan)
>>
>> Changes in  v12->v13:
>> - Add Dave Jiang's, Jonathan's, Ben's review-by
>> - Typo fix (Ben)
>>
>> Changes v11 -> v12:
>> - Documentation requested (Lukas)
>> ---
>>  Documentation/PCI/pci-error-recovery.rst | 2 ++
>>  include/linux/pci.h                      | 3 +++
>>  2 files changed, 5 insertions(+)
>>
>> diff --git a/Documentation/PCI/pci-error-recovery.rst b/Documentation/PCI/pci-error-recovery.rst
>> index 43838723fde9..55be63f1a649 100644
>> --- a/Documentation/PCI/pci-error-recovery.rst
>> +++ b/Documentation/PCI/pci-error-recovery.rst
>> @@ -102,6 +102,8 @@ Possible return values are::
>>  		PCI_ERS_RESULT_NEED_RESET,  /* Device driver wants slot to be reset. */
>>  		PCI_ERS_RESULT_DISCONNECT,  /* Device has completely failed, is unrecoverable */
>>  		PCI_ERS_RESULT_RECOVERED,   /* Device driver is fully recovered and operational */
>> +		PCI_ERS_RESULT_NO_AER_DRIVER, /* No AER capabilities registered for the driver */
>> +		PCI_ERS_RESULT_PANIC,       /* System is unstable, panic. Is CXL specific */
>>  	};
>>  
>>  A driver does not have to implement all of these callbacks; however,
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index 1c270f1d5123..0d6ad11e3422 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -933,6 +933,9 @@ enum pci_ers_result {
>>  
>>  	/* No AER capabilities registered for the driver */
>>  	PCI_ERS_RESULT_NO_AER_DRIVER = (__force pci_ers_result_t) 6,
>> +
>> +	/* System is unstable, panic. Is CXL specific */
> 
> I will note that panic from error reporting is not a CXL specific
> phenomenon. One of the future topics to resolve is indeed the
> discrepency between ACPI/GHES and PCI/AER. PCI/AER does not panic in
> situations that ACPI/GHES does (see ghes_panic()).
> 
> I also notice that helpful TODO in drivers/pci/pcie/err.c was removed
> by:
> 
> b06d125e6280 ("PCI/ERR: Remove misleading TODO regarding kernel panic")
> 
> ...which did not make any comment on that mismatch.

I felt it was important to inform the reader that panic is not used or implemented
yet for non-CXL devices. I will remove the CXL reference in the panic definition.
I cant find commit b06d125e6280.

- Terry