[PATCH] drm/ttm: warn when resv objs are mixed in a bulk_move

[Thomas Hellström]

From: Christian König <ckoenig.leichtzumerken at gmail.com>

The BOs in a bulk move must share all the same reservation object
to make sure that we lock the whole bulk during eviction.

Actually document and enforce that with a warning.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/ttm/ttm_resource.c | 1 +
 include/drm/ttm/ttm_resource.h     | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 65155f2013ca..be8d286513f9 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -105,6 +105,7 @@ static void ttm_lru_bulk_move_add(struct ttm_lru_bulk_move *bulk,
 		pos->first = res;
 		pos->last = res;
 	} else {
+		WARN_ON(pos->first->bo->base.resv != res->bo->base.resv);
 		ttm_lru_bulk_move_pos_tail(pos, res);
 	}
 }
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index 7561023db43d..69769355139f 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -251,6 +251,9 @@ struct ttm_lru_bulk_move_pos {
  *
  * Container for the current bulk move state. Should be used with
  * ttm_lru_bulk_move_init() and ttm_bo_set_bulk_move().
+ * All BOs in a bulk_move structure need to share the same reservation object to
+ * ensure that the bulk as a whole is locked for eviction even if only one BO of
+ * the bulk is evicted.
  */
 struct ttm_lru_bulk_move {
 	struct ttm_lru_bulk_move_pos pos[TTM_NUM_MEM_TYPES][TTM_MAX_BO_PRIORITY];
-- 
2.44.0