Re: [PATCH 10/14] drm/amdgpu/vm: Use init PTE flags and NOALLOC in amdgpu_vm_handle_fault()

["Christian König" <christian.koenig@amd.com>]

On 7/1/26 18:17, Timur Kristóf wrote:
> PTE_IS_PTE seems necessary for handling retry faults on GFX12.
> 
> For reference see:
> amdgpu_vm_pte_update_flags() that explains the problem
> svm_range_get_pte_flags() that uses the flag on GFX12
> 
> Also add NOALLOC on GFX10.3+ as we don't need to allocate
> the fault handling PTE in the infinity cache (MALL).
> 
> Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 32719f31b6c9..a915d061085f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -3044,7 +3044,8 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
>  	}
>  
>  	addr /= AMDGPU_GPU_PAGE_SIZE;
> -	flags = AMDGPU_PTE_VALID | AMDGPU_PTE_SNOOPED |
> +	flags = adev->gmc.init_pte_flags |
> +		AMDGPU_PTE_VALID | AMDGPU_PTE_SNOOPED |
>  		AMDGPU_PTE_SYSTEM;

That doesn't make sense the PTE flags should be adjusted to the device specific flags by the callbacks.

>  
>  	if (is_compute_context) {
> @@ -3054,11 +3055,14 @@ bool amdgpu_vm_handle_fault(struct amdgpu_device *adev, u32 pasid,
>  		flags = AMDGPU_VM_NORETRY_FLAGS;
>  		value = 0;
>  	} else if (amdgpu_vm_fault_stop == AMDGPU_VM_FAULT_STOP_NEVER) {
> +		/* Don't allocate this PTE in the MALL */
> +		if (amdgpu_ip_version(adev, GC_HWIP, 0) >= IP_VERSION(10, 3, 0))
> +			flags |= AMDGPU_PTE_NOALLOC;
> +

This doesn't make sense either, mall allocation for the dummy page should be perfectly fine.

Regards,
Christian.

>  		/* Redirect the access to the dummy page */
>  		value = adev->dummy_page_addr;
>  		flags |= AMDGPU_PTE_EXECUTABLE | AMDGPU_PTE_READABLE |
>  			AMDGPU_PTE_WRITEABLE;
> -
>  	} else {
>  		/* Let the hw retry silently on the PTE */
>  		value = 0;