drm/ttm: audit bo->resource usage v2

Allow BOs to exist without backing store.

v2: handle ttm_bo_move_memcpy as well.
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/20220707102453.3633-5-christian.koenig@amd.com

drivers/gpu/drm/ttm/ttm_bo.c

@@ -117,12 +117,13 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 				  struct ttm_operation_ctx *ctx,
 				  struct ttm_place *hop)
 {
-	struct ttm_resource_manager *old_man, *new_man;
 	struct ttm_device *bdev = bo->bdev;
+	bool old_use_tt, new_use_tt;
 	int ret;
 
-	old_man = ttm_manager_type(bdev, bo->resource->mem_type);
-	new_man = ttm_manager_type(bdev, mem->mem_type);
+	old_use_tt = bo->resource &&
+		ttm_manager_type(bdev, bo->resource->mem_type)->use_tt;
+	new_use_tt = ttm_manager_type(bdev, mem->mem_type)->use_tt;
 
 	ttm_bo_unmap_virtual(bo);
 
@@ -130,11 +131,11 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 	 * Create and bind a ttm if required.
 	 */
 
-	if (new_man->use_tt) {
+	if (new_use_tt) {
 		/* Zero init the new TTM structure if the old location should
 		 * have used one as well.
 		 */
-		ret = ttm_tt_create(bo, old_man->use_tt);
+		ret = ttm_tt_create(bo, old_use_tt);
 		if (ret)
 			goto out_err;
 
@@ -160,8 +161,7 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 	return 0;
 
 out_err:
-	new_man = ttm_manager_type(bdev, bo->resource->mem_type);
-	if (!new_man->use_tt)
+	if (!old_use_tt)
 		ttm_bo_tt_destroy(bo);
 
 	return ret;
@@ -898,7 +898,7 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 	/*
 	 * Check whether we need to move buffer.
 	 */
-	if (!ttm_resource_compat(bo->resource, placement)) {
+	if (!bo->resource || !ttm_resource_compat(bo->resource, placement)) {
 		ret = ttm_bo_move_buffer(bo, placement, ctx);
 		if (ret)
 			return ret;

drivers/gpu/drm/ttm/ttm_bo_util.c

@@ -137,8 +137,7 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 		ttm_manager_type(bo->bdev, dst_mem->mem_type);
 	struct ttm_tt *ttm = bo->ttm;
 	struct ttm_resource *src_mem = bo->resource;
-	struct ttm_resource_manager *src_man =
-		ttm_manager_type(bdev, src_mem->mem_type);
+	struct ttm_resource_manager *src_man;
 	union {
 		struct ttm_kmap_iter_tt tt;
 		struct ttm_kmap_iter_linear_io io;
@@ -147,6 +146,10 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 	bool clear;
 	int ret = 0;
 
+	if (!src_mem)
+		return 0;
+
+	src_man = ttm_manager_type(bdev, src_mem->mem_type);
 	if (ttm && ((ttm->page_flags & TTM_TT_FLAG_SWAPPED) ||
 		    dst_man->use_tt)) {
 		ret = ttm_tt_populate(bdev, ttm, ctx);