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drm/xe/dma_buf: stop relying on placement in unmap

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commit 25583ad42d091819157832e894179200ba8b54ee upstream.

The is_vram() is checking the current placement, however if we consider
exported VRAM with dynamic dma-buf, it looks possible for the xe driver
to async evict the memory, notifying the importer, however importer does
not have to call unmap_attachment() immediately, but rather just as
"soon as possible", like when the dma-resv idles. Following from this we
would then pipeline the move, attaching the fence to the manager, and
then update the current placement. But when the unmap_attachment() runs
at some later point we might see that is_vram() is now false, and take
the complete wrong path when dma-unmapping the sg, leading to
explosions.

To fix this check if the sgl was mapping a struct page.

v2:
  - The attachment can be mapped multiple times it seems, so we can't
    really rely on encoding something in the attachment->priv. Instead
    see if the page_link has an encoded struct page. For vram we expect
    this to be NULL.

Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/4563
Fixes: dd08ebf6c3 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <stable@vger.kernel.org> # v6.8+
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/r/20250410162716.159403-2-matthew.auld@intel.com
(cherry picked from commit d755887f8e5a2a18e15e6632a5193e5feea18499)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Matthew Auld
2025-04-10 17:27:17 +01:00
committed by Greg Kroah-Hartman
parent e97bf44115
commit e4ed75e974
1 changed files with 1 additions and 4 deletions
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5
drivers/gpu/drm/xe/xe_dma_buf.c
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@@ -145,10 +145,7 @@ static void xe_dma_buf_unmap(struct dma_buf_attachment *attach,
struct sg_table *sgt,
enum dma_data_direction dir)
{
struct dma_buf *dma_buf = attach->dmabuf;
struct xe_bo *bo = gem_to_xe_bo(dma_buf->priv);
if (!xe_bo_is_vram(bo)) {
if (sg_page(sgt->sgl)) {
dma_unmap_sgtable(attach->dev, sgt, dir, 0);
sg_free_table(sgt);
kfree(sgt);