Am 05.01.21 um 19:12 schrieb Lyude Paul:

Reviewed-by: Lyude Paul lyude@redhat.com

Guessing it's fine if I push this with your sob and review added?

Works for me, just take care that you pick the right branch.

I always seem to push my stuff into the wrong one.

Christian.

On Tue, 2021-01-05 at 12:45 +0100, Christian König wrote:

...

From: Lyude Paul lyude@redhat.com

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@redhat.com Fixes: 3d1a88e1051f ("drm/ttm: cleanup LRU handling further") Cc: Christian König christian.koenig@amd.com Cc: Dave Airlie airlied@redhat.com

---

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]);