Re: [PATCH v2] drm/amdgpu: bind imported BOs before mapping them into a VM

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

On 8/11/26 10:07, Yifan Zhang wrote:
> From: Prerona Ghosh <Prerona.Ghosh@amd.com>
> 
> An imported dma-buf with a dynamic attachment is not bound to GTT until
> it is validated. In a VM that is not a KFD compute context nothing does
> that: amdgpu_gem_object_open() only validates and fences imports for
> compute VMs, and clients submitting through HW queues never go through
> amdgpu_cs, so amdgpu_vm_validate() does not run either.

Well that is a good catch, but clear NAK to this hacky workaround.

I suggested a long time ago already to change this behavior and validate inside amdgpu_gem_object_open(), IIRC we even had patches for that on the mailing list.

Did we accidentally dropped those?

Regards,
Christian.

> 
> AMDGPU_GEM_VA then maps the BO while its resource is still
> TTM_PL_SYSTEM. amdgpu_ttm_tt_pde_flags() drops AMDGPU_PTE_VALID and
> AMDGPU_PTE_SYSTEM for that memory type, so the range is programmed with
> PTE flags 0x60 (readable and writeable only) and the first GPU access to
> it faults:
> 
>  amdgpu 0000:26:00.0: [gfxhub0] retry page fault (src_id:0 ring:0 vmid:3 pasid:46)
>  amdgpu 0000:26:00.0:   in page starting at address 0x00007f142d6d8000 from IH client 0x1b (UTCL2)
>  amdgpu 0000:26:00.0: VM_L2_PROTECTION_FAULT_STATUS:0x00301011
>  amdgpu 0000:26:00.0:      Faulty UTCL2 client ID: TCP (0x8)
>  amdgpu 0000:26:00.0:      PERMISSION_FAULTS: 0x1
> 
> Validate imported BOs into their allowed domains before MAP and REPLACE
> so that the mapping is always created from a bound resource.
> 
> Signed-off-by: Yifan Zhang <yifan1.zhang@amd.com>
> Assisted-by: Claude:opus-5
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 29 +++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index f754a4a3a1c2..214ae2a95da2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -747,6 +747,27 @@ int amdgpu_gem_metadata_ioctl(struct drm_device *dev, void *data,
>  	return r;
>  }
>  
> +/**
> + * amdgpu_gem_va_make_resident - bind an imported BO before it gets mapped
> + *
> + * @bo: the BO about to be mapped into a VM
> + *
> + * Imported dma-bufs with a dynamic attachment stay unbound until they are
> + * validated. Mapping one while it is still in TTM_PL_SYSTEM would program
> + * PTEs without AMDGPU_PTE_VALID and any GPU access to them faults.
> + */
> +static int amdgpu_gem_va_make_resident(struct amdgpu_bo *bo)
> +{
> +	struct ttm_operation_ctx ctx = { true, false };
> +
> +	if (bo->tbo.resource &&
> +	    bo->tbo.resource->mem_type != TTM_PL_SYSTEM)
> +		return 0;
> +
> +	amdgpu_bo_placement_from_domain(bo, bo->allowed_domains);
> +	return ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
> +}
> +
>  /**
>   * amdgpu_gem_va_update_vm -update the bo_va in its VM
>   *
> @@ -962,6 +983,14 @@ int amdgpu_gem_va_ioctl(struct drm_device *dev, void *data,
>  	if (r)
>  		goto error;
>  
> +	if (abo && drm_gem_is_imported(&abo->tbo.base) &&
> +	    (args->operation == AMDGPU_VA_OP_MAP ||
> +	     args->operation == AMDGPU_VA_OP_REPLACE)) {
> +		r = amdgpu_gem_va_make_resident(abo);
> +		if (r)
> +			goto error;
> +	}
> +
>  	switch (args->operation) {
>  	case AMDGPU_VA_OP_MAP:
>  		r = amdgpu_vm_bo_map(adev, bo_va, args->va_address,