[PATCH v6 09/12] drm/xe/dma_buf: Block export of DONTNEED/purged BOs

Arvind Yadav
2026-03-03T15:20:58Z

Don't allow exporting BOs marked DONTNEED or PURGED as dma-bufs.
DONTNEED BOs can have their contents discarded at any time, making
the exported dma-buf unusable for external devices. PURGED BOs have
no backing store and are permanently invalid.

Return -EBUSY for DONTNEED BOs (temporary purgeable state) and
-EINVAL for purged BOs (permanent, no backing store).

The export path now checks the BO's purgeable state before creating
the dma-buf, preventing external devices from accessing memory that
may be purged at any time.

v6:
- Split DONTNEED → -EBUSY and PURGED → -EINVAL for consistency
with the rest of the series (Thomas, Matt)

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
---
drivers/gpu/drm/xe/xe_dma_buf.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c
index ea370cd373e9..aba6b9696030 100644
--- a/drivers/gpu/drm/xe/xe_dma_buf.c
+++ b/drivers/gpu/drm/xe/xe_dma_buf.c
@@ -223,6 +223,23 @@ struct dma_buf *xe_gem_prime_export(struct drm_gem_object *obj, int flags)
if (bo->vm)
return ERR_PTR(-EPERM);

+ /*
+ * Reject exporting purgeable BOs. DONTNEED BOs can be purged
+ * at any time, making the exported dma-buf unusable. Purged BOs
+ * have no backing store and are permanently invalid.
+ */
+ xe_bo_lock(bo, false);
+ if (xe_bo_madv_is_dontneed(bo)) {
+ ret = -EBUSY;
+ goto out_unlock;
+ }
+
+ if (xe_bo_is_purged(bo)) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ xe_bo_unlock(bo);
+
ret = ttm_bo_setup_export(&bo->ttm, &ctx);
if (ret)
return ERR_PTR(ret);
@@ -232,6 +249,10 @@ struct dma_buf *xe_gem_prime_export(struct drm_gem_object *obj, int flags)
buf->ops = &xe_dmabuf_ops;

return buf;
+
+out_unlock:
+ xe_bo_unlock(bo);
+ return ERR_PTR(ret);
}

static struct drm_gem_object *
--
2.43.0