Re: [PATCH v5 07/16] PCI/AER: Add CXL PCIe Port uncorrectable error recovery in AER service driver

Bowman, Terry
2025-01-14T20:28:19Z

On 1/14/2025 5:33 AM, Jonathan Cameron wrote:
> On Tue, 7 Jan 2025 08:38:43 -0600
> Terry Bowman <terry.bowman@amd.com> wrote:
>
>> Existing recovery procedure for PCIe uncorrectable errors (UCE) does not
>> apply to CXL devices. Recovery can not be used for CXL devices because of
>> potential corruption on what can be system memory. Also, current PCIe UCE
>> recovery, in the case of a Root Port (RP) or Downstream Switch Port (DSP),
>> does not begin at the RP/DSP but begins at the first downstream device.
>> This will miss handling CXL Protocol Errors in a CXL RP or DSP. A separate
>> CXL recovery is needed because of the different handling requirements
>>
>> Add a new function, cxl_do_recovery() using the following.
>>
>> Add cxl_walk_bridge() to iterate the detected error's sub-topology.
>> cxl_walk_bridge() is similar to pci_walk_bridge() but the CXL flavor
>> will begin iteration at the RP or DSP rather than beginning at the
>> first downstream device.
> I'm still holding out for making pci_walk_bridge() do the same and seeing
> what if anything breaks.

I can test AER fatal UCE on a PCIe device. Do you have any other ideas for specific
testing? A specific device or topology in mind ?

Regards,
Terry

> Other than that I'm fine with this patch.
>
>> Add cxl_report_error_detected() as an analog to report_error_detected().
>> It will call pci_driver::cxl_err_handlers for each iterated downstream
>> device. The pci_driver::cxl_err_handler's UCE handler returns a boolean
>> indicating if there was a UCE error detected during handling.
>>
>> cxl_do_recovery() uses the status from cxl_report_error_detected() to
>> determine how to proceed. Non-fatal CXL UCE errors will be treated as
>> fatal. If a UCE was present during handling then cxl_do_recovery()
>> will kernel panic.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>