Re: [Bug 216373] New: Uncorrected errors reported for AMD GPU

[Bjorn Helgaas <helgaas@kernel.org>]

[Adding amdgpu folks]

On Wed, Aug 17, 2022 at 11:45:15PM +0000, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=216373
> 
>             Bug ID: 216373
>            Summary: Uncorrected errors reported for AMD GPU
>     Kernel Version: v6.0-rc1
>         Regression: No
> ...

I marked this as a regression in bugzilla.

> Hardware:
> CPU: Intel i7-12700K (Alder Lake)
> GPU: AMD RX 6700 XT [1002:73df]
> Motherboard: ASUS Prime Z690-A
> 
> Problem:
> After upgrading to v6.0-rc1 the kernel is now reporting uncorrected PCI errors
> for my GPU.

Thank you very much for the report and for taking the trouble to
bisect it and test Kai-Heng's patch!

I suspect that booting with "pci=noaer" should be a temporary
workaround for this issue.  If it, can you add that to the bugzilla
for anybody else who trips over this?

> I have bisected this issue to: [8795e182b02dc87e343c79e73af6b8b7f9c5e635]
> PCI/portdrv: Don't disable AER reporting in get_port_device_capability()
> Reverting that commit causes the errors to cease.

I suspect the errors still occur, but we just don't notice and log
them.

> I have also tried Kai-Heng Feng's patch[1] which seems to resolve a similar
> problem, but it did not fix my issue.
> 
> [1]
> https://lore.kernel.org/linux-pci/20220706123244.18056-1-kai.heng.feng@canonical.com/
>
> dmesg snippet:
> 
> pcieport 0000:00:01.0: AER: Multiple Uncorrected (Non-Fatal) error received:
> 0000:03:00.0
> amdgpu 0000:03:00.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal),
> type=Transaction Layer, (Requester ID)
> amdgpu 0000:03:00.0:   device [1002:73df] error status/mask=00100000/00000000
> amdgpu 0000:03:00.0:    [20] UnsupReq               (First)
> amdgpu 0000:03:00.0: AER:   TLP Header: 40000001 0000000f 95e7f000 00000000

I think the TLP header decodes to:

  0x40000001 = 0100 0000 ... 0000 0001 binary
  0x0000000f = 0000 0000 ... 0000 1111 binary

  Fmt           010b                 3 DW header with data
  Type          0000b  010 0 0000    MWr Memory Write Request
  Length        00 0000 0001b        1 DW
  Requester ID  0x0000               00:00.0
  Tag           0x00
  Last DW BE    0000b                must be zero for 1 DW write
  First DW BE   1111b                all 4 bytes in DW enabled
  Address       0x95e7f000
  Data          0x00000000

So I think this is a 32-bit write of zero to PCI bus address
0x95e7f000.

Your dmesg log says:

  pci 0000:02:00.0: PCI bridge to [bus 03]
  pci 0000:02:00.0:   bridge window [mem 0x95e00000-0x95ffffff]
  pci 0000:03:00.0: reg 0x24: [mem 0x95e00000-0x95efffff]
  [drm] register mmio base: 0x95E00000

So this looks like a write to the device's BAR 5.  I don't see a PCI
reason why this should fail.  Maybe there's some amdgpu reason?

Bjorn