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

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Date:   Wed, 25 Jan 2017 16:46:33 -0800
From:   Sinclair Yeh <syeh@...are.com>
To:     Christian König <christian.koenig@....com>
CC:     Thomas Hellstrom <thellstrom@...are.com>,
        Michel Dänzer <michel@...nzer.net>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/ttm: Make sure BOs being swapped out are cacheable

On Wed, Jan 25, 2017 at 10:49:33AM +0100, Christian König wrote:
> Am 25.01.2017 um 10:25 schrieb Thomas Hellstrom:
> >On 01/25/2017 09:21 AM, Michel Dänzer wrote:
> >>From: Michel Dänzer <michel.daenzer@....com>
> >>
> >>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.
> >>
> >>Cc: stable@...r.kernel.org
> >>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>

> 
> >
> >>---
> >>  drivers/gpu/drm/ttm/ttm_bo.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> >>index d5063618efa7..86e3b233b722 100644
> >>--- a/drivers/gpu/drm/ttm/ttm_bo.c
> >>+++ b/drivers/gpu/drm/ttm/ttm_bo.c
> >>@@ -1670,7 +1670,6 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink)
> >>  	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) {
> >>@@ -1701,7 +1700,8 @@ static int ttm_bo_swapout(struct ttm_mem_shrink *shrink)
> >>  	 * Move to system cached
> >>  	 */
> >>-	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;
> >
>