Commit 63cf199c authored by Arvind Yadav's avatar Arvind Yadav Committed by Matthew Brost
Browse files

drm/xe/madvise: Block imported and exported dma-bufs 



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.

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Reviewed-by: default avatarThomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: default avatarArvind Yadav <arvind.yadav@intel.com>
Signed-off-by: default avatarMatthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20260326130843.3545241-8-arvind.yadav@intel.com
parent 5bfb7e6a

drivers/gpu/drm/xe/xe_vm_madvise.c

+37 −0
Original line number Diff line number Diff line
@@ -185,6 +185,33 @@ static void madvise_pat_index(struct xe_device *xe, struct xe_vm *vm, 
	}

}



/**

 * xe_bo_is_dmabuf_shared() - Check if BO is shared via dma-buf

 * @bo: Buffer object

 *

 * Prevent marking imported or exported dma-bufs as purgeable.

 * For imported BOs, Xe doesn't own the backing store and cannot

 * safely reclaim pages (exporter or other devices may still be

 * using them). For exported BOs, external devices may have active

 * mappings we cannot track.

 *

 * Return: true if BO is imported or exported, false otherwise

 */

static bool xe_bo_is_dmabuf_shared(struct xe_bo *bo)

{

	struct drm_gem_object *obj = &bo->ttm.base;



	/* Imported: exporter owns backing store */

	if (drm_gem_is_imported(obj))

		return true;



	/* Exported: external devices may be accessing */

	if (obj->dma_buf)

		return true;



	return false;

}



/**

 * enum xe_bo_vmas_purge_state - VMA purgeable state aggregation

 *
@@ -234,6 +261,10 @@ static enum xe_bo_vmas_purge_state xe_bo_all_vmas_dontneed(struct xe_bo *bo) 


	xe_bo_assert_held(bo);



	/* Shared dma-bufs cannot be purgeable */

	if (xe_bo_is_dmabuf_shared(bo))

		return XE_BO_VMAS_STATE_WILLNEED;



	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);
@@ -335,6 +366,12 @@ static void __maybe_unused madvise_purgeable(struct xe_device *xe, 
		/* BO must be locked before modifying madv state */

		xe_bo_assert_held(bo);



		/* Skip shared dma-bufs - no PTEs to zap */

		if (xe_bo_is_dmabuf_shared(bo)) {

			vmas[i]->skip_invalidation = true;

			continue;

		}



		/*

		 * Once purged, always purged. Cannot transition back to WILLNEED.

		 * This matches i915 semantics where purged BOs are permanently invalid.