drm/xe/dma_buf: Block export of DONTNEED/purged BOs

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.

Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Arvind Yadav <arvind.yadav@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260326130843.3545241-10-arvind.yadav@intel.com

diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c
index ea370cd373e98123af58ed95da299e9b7b6720e0..7f9602b3363db1433cd596e2b41e2bdb34c1ca2d 100644 (file)
--- a/drivers/gpu/drm/xe/xe_dma_buf.c
+++ b/drivers/gpu/drm/xe/xe_dma_buf.c
@@ -223,6 +223,26 @@ 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.
+        */
+       ret = xe_bo_lock(bo, true);
+       if (ret)
+               return ERR_PTR(ret);
+
+       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 +252,10 @@ 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 *