linux-kernel - [PATCH 3.16 077/212] drm/ttm: Make sure BOs being swapped out are cacheable

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Date:   Thu, 01 Jun 2017 16:43:16 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Michel Dänzer" <michel.daenzer@....com>,
        "Thomas Hellstrom" <thellstrom@...are.com>,
        "Christian König" <christian.koenig@....com>,
        "Sinclair Yeh" <syeh@...are.com>
Subject: [PATCH 3.16 077/212] drm/ttm: Make sure BOs being swapped out are
 cacheable

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Michel Dänzer <michel.daenzer@....com>

commit 239ac65fa5ffab71adf66e642750f940e7241d99 upstream.

The current caching state may not be tt_cached, even though the
placement contains TTM_PL_FLAG_CACHED, because placement can contain
multiple caching flags. Trying to swap out such a BO would trip up the

	BUG_ON(ttm->caching_state != tt_cached);

in ttm_tt_swapout.

Signed-off-by: Michel Dänzer <michel.daenzer@....com>
Reviewed-by: Thomas Hellstrom <thellstrom@...are.com>
Reviewed-by: Christian König <christian.koenig@....com>.
Reviewed-by: Sinclair Yeh <syeh@...are.com>
Signed-off-by: Christian König <christian.koenig@....com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/gpu/drm/ttm/ttm_bo.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -1641,7 +1641,6 @@ static int ttm_bo_swapout(struct ttm_mem
 	struct ttm_buffer_object *bo;
 	int ret = -EBUSY;
 	int put_count;
-	uint32_t swap_placement = (TTM_PL_FLAG_CACHED | TTM_PL_FLAG_SYSTEM);
 
 	spin_lock(&glob->lru_lock);
 	list_for_each_entry(bo, &glob->swap_lru, swap) {
@@ -1679,7 +1678,8 @@ static int ttm_bo_swapout(struct ttm_mem
 	if (unlikely(ret != 0))
 		goto out;
 
-	if ((bo->mem.placement & swap_placement) != swap_placement) {
+	if (bo->mem.mem_type != TTM_PL_SYSTEM ||
+	    bo->ttm->caching_state != tt_cached) {
 		struct ttm_mem_reg evict_mem;
 
 		evict_mem = bo->mem;