On 11/6/25 18:03, [email protected] wrote:
> From: Vitaly Prosyak <[email protected]>
>
> Certain multi-GPU configurations (especially GFX12) may hit
> data corruption when a DCC-compressed VRAM surface is shared across GPUs
> using peer-to-peer (P2P) DMA transfers.
>
> Such surfaces rely on device-local metadata and cannot be safely accessed
> through a remote GPU’s page tables. Attempting to import a DCC-enabled
> surface through P2P leads to incorrect rendering or GPU faults.
>
> This change disables P2P for DCC-enabled VRAM buffers that are contiguous
> and allocated on GFX12+ hardware. In these cases, the importer falls back
> to the standard system-memory path, avoiding invalid access to compressed
> surfaces.
>
> Future work could consider optional migration (VRAM→System→VRAM) if a
> performance regression is observed when `attach->peer2peer = false`.
>
> Tested on:
> - Dual RX 9700 XT (Navi4x) setup
> - GNOME and Wayland compositor scenarios
> - Confirmed no corruption after disabling P2P under these conditions
>
> Suggested-by: Christian König <[email protected]>
> Signed-off-by: Vitaly Prosyak <[email protected]>
Reviewed-by: Christian König <[email protected]>
> ---
> drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index 9a0bce3ba24c..d2d31031f672 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -260,11 +260,24 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
> struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>
> #ifdef HAVE_STRUCT_DMA_BUF_ATTACH_OPS_ALLOW_PEER2PEER
> + /*
> + * Disable peer-to-peer access for DCC-enabled VRAM surfaces on GFX12+.
> + * Such buffers cannot be safely accessed over P2P due to device-local
> + * compression metadata. Fallback to system-memory path instead.
> + * Device supports GFX12 (GC 12.x or newer)
> + * BO was created with the AMDGPU_GEM_CREATE_GFX12_DCC flag
> + *
> + */
> + if ((adev->ip_versions[GC_HWIP][0] >= IP_VERSION(12, 0, 0)) &&
> + bo->flags & AMDGPU_GEM_CREATE_GFX12_DCC) {
> + attach->peer2peer = false;
> + goto update_vm;
> + }
> if (!amdgpu_dmabuf_is_xgmi_accessible(attach_adev, bo) &&
> pci_p2pdma_distance(adev->pdev, attach->dev, false) < 0)
> attach->peer2peer = false;
> #endif
> -
> +update_vm:
> amdgpu_vm_bo_update_shared(bo);
>
> return 0;
