[PATCH v4 7/8] drm/xe/madvise: Block imported and exported dma-bufs

Arvind Yadav
2026-01-20T06:09:31Z

Prevent marking imported or exported dma-bufs as purgeable.
External devices may be accessing these buffers without our
knowledge, making purging unsafe.

Check drm_gem_is_imported() for buffers created by other
drivers and obj->dma_buf for buffers exported to other
drivers. Silently skip these BOs during madvise processing.

This follows drm_gem_shmem's purgeable implementation and
prevents data corruption from purging actively-used shared
buffers.

v3:
- Addresses review feedback from Matt Roper about handling
imported/exported BOs correctly in the purgeable BO
implementation.

v4:
- Check should be add to xe_vm_madvise_purgeable_bo.

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_vm_madvise.c | 33 ++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_vm_madvise.c b/drivers/gpu/drm/xe/xe_vm_madvise.c
index 27b6ad65b314..5808fef89777 100644
--- a/drivers/gpu/drm/xe/xe_vm_madvise.c
+++ b/drivers/gpu/drm/xe/xe_vm_madvise.c
@@ -180,6 +180,31 @@ static void madvise_pat_index(struct xe_device *xe, struct xe_vm *vm,
}
}

+/**
+ * xe_bo_is_external_dmabuf() - Check if BO is imported or exported dma-buf
+ * @bo: Buffer object
+ *
+ * Prevent marking imported or exported dma-bufs as purgeable.
+ * External devices may be accessing these buffers without our
+ * knowledge, making purging unsafe.
+ *
+ * Return: true if BO is imported or exported, false otherwise
+ */
+static bool xe_bo_is_external_dmabuf(struct xe_bo *bo)
+{
+ struct drm_gem_object *obj = &bo->ttm.base;
+
+ /* Imported from another driver */
+ if (drm_gem_is_imported(obj))
+ return true;
+
+ /* Exported to another driver */
+ if (obj->dma_buf)
+ return true;
+
+ return false;
+}
+
/**
* xe_bo_all_vmas_dontneed() - Check if all VMAs of a BO are marked DONTNEED
* @bo: Buffer object
@@ -200,6 +225,10 @@ static bool xe_bo_all_vmas_dontneed(struct xe_bo *bo)

dma_resv_assert_held(bo->ttm.base.resv);

+ /* External dma-bufs cannot be purgeable */
+ if (xe_bo_is_external_dmabuf(bo))
+ return false;
+
drm_gem_for_each_gpuvm_bo(vm_bo, obj) {
drm_gpuvm_bo_for_each_va(gpuva, vm_bo) {
struct xe_vma *vma = gpuva_to_vma(gpuva);
@@ -277,6 +306,10 @@ static bool xe_vm_madvise_purgeable_bo(struct xe_device *xe, struct xe_vm *vm,
/* BO must be locked before modifying madv state */
xe_bo_assert_held(bo);

+ /* Skip external dma-bufs */
+ if (xe_bo_is_external_dmabuf(bo))
+ continue;
+
/*
* Once purged, always purged. Cannot transition back to WILLNEED.
* This matches i915 semantics where purged BOs are permanently invalid.
--
2.43.0