drm/amdgpu: make sure that BOs have a backing store

It's perfectly possible that the BO is about to be destroyed and doesn't
have a backing store associated with it.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Guchun Chen <guchun.chen@amd.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_object.c

@@ -1282,8 +1282,12 @@ void amdgpu_bo_move_notify(struct ttm_buffer_object *bo,
 void amdgpu_bo_get_memory(struct amdgpu_bo *bo,
 			  struct amdgpu_mem_stats *stats)
 {
-	unsigned int domain;
 	uint64_t size = amdgpu_bo_size(bo);
+	unsigned int domain;
+
+	/* Abort if the BO doesn't currently have a backing store */
+	if (!bo->tbo.resource)
+		return;
 
 	domain = amdgpu_mem_type_to_domain(bo->tbo.resource->mem_type);
 	switch (domain) {