drm/amdgpu: audit bo->resource usage

Make sure we can at least move and release BOs without backing store.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220707102453.3633-3-christian.koenig@amd.com

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

@@ -1305,7 +1305,7 @@ void amdgpu_bo_release_notify(struct ttm_buffer_object *bo)
 	if (bo->base.resv == &bo->base._resv)
 		amdgpu_amdkfd_remove_fence_on_pt_pd_bos(abo);
 
-	if (bo->resource->mem_type != TTM_PL_VRAM ||
+	if (!bo->resource || bo->resource->mem_type != TTM_PL_VRAM ||
 	    !(abo->flags & AMDGPU_GEM_CREATE_VRAM_WIPE_ON_RELEASE) ||
 	    adev->in_suspend || adev->shutdown)
 		return;

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

@@ -471,7 +471,8 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 
 	adev = amdgpu_ttm_adev(bo->bdev);
 
-	if (old_mem->mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
+	if (!old_mem || (old_mem->mem_type == TTM_PL_SYSTEM &&
+			 bo->ttm == NULL)) {
 		ttm_bo_move_null(bo, new_mem);
 		goto out;
 	}