On 11.09.25 16:38, Srinivasan Shanmugam wrote: > The HDP flush page (AMDGPU_PL_MMIO_REMAP) is an MMIO window, not RAM. > It must not be migrated to GTT/VRAM by dma-buf paths. > > This change makes pin/unpin no-ops for MMIO_REMAP and skips CPU-access > migration, keeping the object fixed.
Just use ttm_bo_pin() while creating the BO, no need to modify anything here. Regards, Christian. > > Cc: Christian König <christian.koe...@amd.com> > Cc: Alex Deucher <alexander.deuc...@amd.com> > Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com> > --- > drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > index 31d78561ab95..4c75e296b57f 100644 > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c > @@ -109,6 +109,11 @@ static int amdgpu_dma_buf_pin(struct dma_buf_attachment > *attach) > struct amdgpu_bo *bo = gem_to_amdgpu_bo(dmabuf->priv); > u32 domains = bo->allowed_domains; > > + /* Already pinned at export; don't try to move I/O apertures */ > + if (bo->tbo.resource && > + bo->tbo.resource->mem_type == AMDGPU_PL_MMIO_REMAP) > + return 0; > + > dma_resv_assert_held(dmabuf->resv); > > /* Try pinning into VRAM to allow P2P with RDMA NICs without ODP > @@ -148,6 +153,10 @@ static void amdgpu_dma_buf_unpin(struct > dma_buf_attachment *attach) > struct drm_gem_object *obj = attach->dmabuf->priv; > struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj); > > + if (bo->tbo.resource && > + bo->tbo.resource->mem_type == AMDGPU_PL_MMIO_REMAP) > + return; > + > amdgpu_bo_unpin(bo); > } > > @@ -354,6 +363,11 @@ static int amdgpu_dma_buf_begin_cpu_access(struct > dma_buf *dma_buf, > bool reads = (direction == DMA_BIDIRECTIONAL || > direction == DMA_FROM_DEVICE); > > + /* Never migrate MMIO_REMAP for CPU access heuristics */ > + if (bo->tbo.resource && > + bo->tbo.resource->mem_type == AMDGPU_PL_MMIO_REMAP) > + return 0; > + > if (!reads || !(domain & AMDGPU_GEM_DOMAIN_GTT)) > return 0; >
