Help debug amdgpu faults

[Robert Beckett]

Hi,


does anyone know any documentation, or can provide advice on debugging 
amdgpu fault reports?


e.g:

Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: [gfxhub] 
page fault (src_id:0 ring:8 vmid:1 pasid:32769, for process vkcube pid 
999 thread vkcube pid 999)
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: in page 
starting at address 0x0000800100700000 from client 0x1b (UTCL2)
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: 
GCVM_L2_PROTECTION_FAULT_STATUS:0x00101A10
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: Faulty UTCL2 
client ID: SDMA0 (0xd)
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: MORE_FAULTS: 0x0
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: 
WALKER_ERROR: 0x0
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: 
PERMISSION_FAULTS: 0x1
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: 
MAPPING_ERROR: 0x0
Nov 21 19:17:06 fedora kernel: amdgpu 0000:01:00.0: amdgpu: RW: 0x0



seehttps://gitlab.freedesktop.org/drm/amd/-/issues/2267  for more context.

We have a complicated setup involving rendering then blitting to virtio-gpu exported dmabufs, with plenty of hacks in the mesa and xwayland stacks, so we are considering this our issue to debug, and not an issue with the driver at this point.
However, having debugged all the interesting parts leading to these faults, I am unable to decode the fault report to correlate to a buffer.

in the fault report, what address space is the address from?
given that the fault handler shifts the reported addres up by 12, I assume it is a 4K pfn which makes me assume a physical address is this correct?
if so, is that a vram pa or a host system memory pa?
is there any documentation for the other fields reported like the fault status etc?

I'd appreciate any advice you could give to help us debug further.

Thanks

Bob
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