[PATCH] drm/amdgpu: Update invalid PTE flag setting

[Felix Kuehling]

Am 2023-04-06 um 10:36 schrieb Christian König:
> Am 04.04.23 um 23:59 schrieb Mukul Joshi:
>> Update the invalid PTE flag setting to ensure, in addition
>> to transitioning the retry fault to a no-retry fault, it
>> also causes the wavefront to enter the trap handler. With the
>> current setting, it only transitions to a no-retry fault.
>
> Well that was actually the intended result. Why should it enter the 
> trap handler here?

We need the trap handler for reporting the fault to the debugger. The VM 
fault interrupt itself doesn't provide sufficient information to find 
the wave and the program counter that triggered the fault. It also 
doesn't work well when several waves are faulting on the same address.

Regards,
   Felix


>
>>
>> Signed-off-by: Mukul Joshi <mukul.joshi at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index af6f26a97fc5..5df4f7bb241f 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -2488,7 +2488,7 @@ bool amdgpu_vm_handle_fault(struct 
>> amdgpu_device *adev, u32 pasid,
>>           /* Intentionally setting invalid PTE flag
>>            * combination to force a no-retry-fault
>>            */
>> -        flags = AMDGPU_PTE_SNOOPED | AMDGPU_PTE_PRT;
>> +        flags = AMDGPU_PTE_VALID | AMDGPU_PTE_SYSTEM | AMDGPU_PTE_PRT;
>
> As far as I can see this is actually a valid combination and would not 
> have the desired result.
>
> Regards,
> Christian.
>
>>           value = 0;
>>       } else if (amdgpu_vm_fault_stop == AMDGPU_VM_FAULT_STOP_NEVER) {
>>           /* Redirect the access to the dummy page */
>