[PATCH 1/4] drm/gem-vram: handle NULL bo->resource in move callback

[Matthew Auld]

The ttm BO now initially has NULL bo->resource, and leaves the driver
the handle that. However it looks like we forgot to handle that for
ttm_bo_move_memcpy() users, like with vram-gem, since it just silently
returns zero. This seems to then trigger warnings like:

WARNING: CPU: 0 PID: 1 at drivers/gpu/drm/drm_gem_vram_helper.c:255 drm_gem_vram_offset (??:?)

Fix this by calling move_null() if the new resource is TTM_PL_SYSTEM,
otherwise do the multi-hop sequence to ensure can safely call into
ttm_bo_move_memcpy(), since it might also need to clear the memory.
This should give the same behaviour as before.

While we are here let's also treat calling ttm_bo_move_memcpy() with
NULL bo->resource as programmer error, where expectation is that upper
layers should now handle it.

Fixes: 180253782038 ("drm/ttm: stop allocating dummy resources during BO creation")
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/drm_gem_vram_helper.c | 11 +++++++++++
 drivers/gpu/drm/ttm/ttm_bo_util.c     |  4 ++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_vram_helper.c b/drivers/gpu/drm/drm_gem_vram_helper.c
index d40b3edb52d0..0bea3df2a16d 100644
--- a/drivers/gpu/drm/drm_gem_vram_helper.c
+++ b/drivers/gpu/drm/drm_gem_vram_helper.c
@@ -916,6 +916,17 @@ static int bo_driver_move(struct ttm_buffer_object *bo,
 {
 	struct drm_gem_vram_object *gbo;
 
+	if (!bo->resource) {
+		if (new_mem->mem_type != TTM_PL_SYSTEM) {
+			hop->mem_type = TTM_PL_SYSTEM;
+			hop->flags = TTM_PL_FLAG_TEMPORARY;
+			return -EMULTIHOP;
+		}
+
+		ttm_bo_move_null(bo, new_mem);
+		return 0;
+	}
+
 	gbo = drm_gem_vram_of_bo(bo);
 
 	return drm_gem_vram_bo_driver_move(gbo, evict, ctx, new_mem);
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index d9d2b0903b22..fd9fd3d15101 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -157,8 +157,8 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 	bool clear;
 	int ret = 0;
 
-	if (!src_mem)
-		return 0;
+	if (WARN_ON(!src_mem))
+		return -EINVAL;
 
 	src_man = ttm_manager_type(bdev, src_mem->mem_type);
 	if (ttm && ((ttm->page_flags & TTM_TT_FLAG_SWAPPED) ||
-- 
2.39.1