Re: [PATCH] drm/ttm: fix adding foreign BOs to the LRU during init

[Thomas Hellstrom <thomas@shipmail.org>]

Hi!

I might be misunderderstanding the use-case here, but IIRC the
discussion with TTM vs imported / exported buffer objects is that a
buffer object needs to be marked NO_EVICT in TTM before it's exported
and an imported object should never end up on a LRU list in TTM because
TTM wouldn't know how to evict it.

/Thomas
 

On 01/08/2016 02:41 PM, Christian König wrote:
> From: Christian König <christian.koenig@amd.com>
>
> If we import a BO with an eternal reservation object we don't
> reserve/unreserve it. So we never add it to the LRU causing a possible
> deny of service.
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 745e996..a98a5d5 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -1170,9 +1170,15 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
>  	if (likely(!ret))
>  		ret = ttm_bo_validate(bo, placement, interruptible, false);
>  
> -	if (!resv)
> +	if (!resv) {
>  		ttm_bo_unreserve(bo);
>  
> +	} else if (!(bo->mem.placement & TTM_PL_FLAG_NO_EVICT)) {
> +		spin_lock(&bo->glob->lru_lock);
> +		ttm_bo_add_to_lru(bo);
> +		spin_unlock(&bo->glob->lru_lock);
> +	}
> +
>  	if (unlikely(ret))
>  		ttm_bo_unref(&bo);
>  



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