Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>
Guessing it's fine if I push this with your sob and review added?
On Tue, 2021-01-05 at 12:45 +0100, Christian König wrote:
> From: Lyude Paul <lyude@xxxxxxxxxx>
>
> Recently a regression was introduced which caused TTM's buffer eviction to
> attempt to evict already-pinned BOs, causing issues with buffer eviction
> under memory pressure along with suspend/resume:
>
> nouveau 0000:1f:00.0: DRM: evicting buffers...
> nouveau 0000:1f:00.0: DRM: Moving pinned object 00000000c428c3ff!
> nouveau 0000:1f:00.0: fifo: fault 00 [READ] at 0000000000200000 engine 04
> [BAR1] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel -1 [00ffeaa000
> unknown]
> nouveau 0000:1f:00.0: fifo: DROPPED_MMU_FAULT 00001000
> nouveau 0000:1f:00.0: fifo: fault 01 [WRITE] at 0000000000020000 engine
> 0c [HOST6] client 07 [HUB/HOST_CPU] reason 02 [PTE] on channel 1
> [00ffb28000 DRM]
> nouveau 0000:1f:00.0: fifo: channel 1: killed
> nouveau 0000:1f:00.0: fifo: runlist 0: scheduled for recovery
> [TTM] Buffer eviction failed
> nouveau 0000:1f:00.0: DRM: waiting for kernel channels to go idle...
> nouveau 0000:1f:00.0: DRM: failed to idle channel 1 [DRM]
> nouveau 0000:1f:00.0: DRM: resuming display...
>
> After some bisection and investigation, it appears this resulted from the
> recent changes to ttm_bo_move_to_lru_tail(). Previously when a buffer was
> pinned, the buffer would be removed from the LRU once ttm_bo_unreserve
> to maintain the LRU list when pinning or unpinning BOs. However, since:
>
> commit 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
>
> We've been exiting from ttm_bo_move_to_lru_tail() at the very beginning of
> the function if the bo we're looking at is pinned, resulting in the pinned
> BO never getting removed from the lru and as a result - causing issues when
> it eventually becomes time for eviction.
>
> So, let's fix this by calling ttm_bo_del_from_lru() from
> ttm_bo_move_to_lru_tail() in the event that we're dealing with a pinned
> buffer.
>
> v2 (chk): reduce to only the fixing one liner since we always want to
> call the callback whenever we would move on the LRU.
>
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> Fixes: 3d1a88e1051f ("drm/ttm: cleanup LRU handling further")
> Cc: Christian König <christian.koenig@xxxxxxx>
> Cc: Dave Airlie <airlied@xxxxxxxxxx>
> ---
> drivers/gpu/drm/ttm/ttm_bo.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 31e8b3da5563..b65f4b12f986 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -138,8 +138,10 @@ void ttm_bo_move_to_lru_tail(struct ttm_buffer_object
> *bo,
>
> dma_resv_assert_held(bo->base.resv);
>
> - if (bo->pin_count)
> + if (bo->pin_count) {
> + ttm_bo_del_from_lru(bo);
> return;
> + }
>
> man = ttm_manager_type(bdev, mem->mem_type);
> list_move_tail(&bo->lru, &man->lru[bo->priority]);
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
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