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

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@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit dbe4c63689bc6b5fd3ab72650ea4b6a667e96a68)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
index e6913fcf2c7be2a7a15708c0540cb8b1863d9b4b..44e120f9f76497dd6045e6dea0cda8a03e6ec087 100644 (file)
--- 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);