[PATCH] drm/amdgpu: Fail DMABUF map of XGMI-accessible memory

[Christian König]

Am 17.04.25 um 18:37 schrieb Felix Kuehling:
> If peer memory is XGMI-accessible, we should never access it through PCIe
> P2P DMA mappings. PCIe P2P is slower, has different coherence behaviour,
> limited or no support for atomics, or may not work at all. Fail with a
> warning if DMABUF mappings of such memory are attempted.
>
> Signed-off-by: Felix Kuehling <felix.kuehling at amd.com>

Reviewed-by: Christian König <christian.koenig at amd.com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index e6913fcf2c7b..44e120f9f764 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -199,6 +199,11 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
>  		break;
>  
>  	case TTM_PL_VRAM:
> +		/* XGMI-accessible memory should never be DMA-mapped */
> +		if (WARN_ON(amdgpu_dmabuf_is_xgmi_accessible(
> +				dma_buf_attach_adev(attach), bo)))
> +			return ERR_PTR(-EINVAL);
> +
>  		r = amdgpu_vram_mgr_alloc_sgt(adev, bo->tbo.resource, 0,
>  					      bo->tbo.base.size, attach->dev,
>  					      dir, &sgt);