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

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Message-ID: <e46ca630-ac84-9274-0493-69b983aac789@vmware.com>
Date:   Wed, 25 Jan 2017 10:25:19 +0100
From:   Thomas Hellstrom <thellstrom@...are.com>
To:     Michel Dänzer <michel@...nzer.net>,
        Christian König <christian.koenig@....com>
CC:     <dri-devel@...ts.freedesktop.org>, Sinclair Yeh <syeh@...are.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/ttm: Make sure BOs being swapped out are cacheable

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>

> ---
>  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;