drm/qxl: handle NULL bo->resource in move callback

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 qxl.
It looks like this will just null-ptr-deref in qxl_bo_move(), if
bo->resource is NULL.

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.

Fixes: 180253782038 ("drm/ttm: stop allocating dummy resources during BO creation")
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230208145319.397235-2-matthew.auld@intel.com
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

diff --git a/drivers/gpu/drm/qxl/qxl_ttm.c b/drivers/gpu/drm/qxl/qxl_ttm.c
index a92a5b0d4c25a8daa9a553352ccd17066d30a8ad..1a82629bce3f63323c91c89a06fca3042cd566b3 100644 (file)
--- a/drivers/gpu/drm/qxl/qxl_ttm.c
+++ b/drivers/gpu/drm/qxl/qxl_ttm.c
@@ -143,6 +143,17 @@ static int qxl_bo_move(struct ttm_buffer_object *bo, bool evict,
        struct ttm_resource *old_mem = bo->resource;
        int ret;
 
+       if (!old_mem) {
+               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;
+       }
+
        qxl_bo_move_notify(bo, new_mem);
 
        ret = ttm_bo_wait_ctx(bo, ctx);