linux-kernel - Re: [PATCH] nouveau: explicitly wait on the fence in nouveau_bo_move

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Date:   Mon, 22 Aug 2022 17:15:34 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Karol Herbst <kherbst@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Ben Skeggs <bskeggs@...hat.com>, dri-devel@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org, stable@...r.kernel.org
Subject: Re: [PATCH] nouveau: explicitly wait on the fence in
 nouveau_bo_move_m2mf

Reviewed-by: Lyude Paul <lyude@...hat.com>

On Fri, 2022-08-19 at 22:09 +0200, Karol Herbst wrote:
> It is a bit unlcear to us why that's helping, but it does and unbreaks
> suspend/resume on a lot of GPUs without any known drawbacks.
> 
> Cc: stable@...r.kernel.org # v5.15+
> Closes: https://gitlab.freedesktop.org/drm/nouveau/-/issues/156
> Signed-off-by: Karol Herbst <kherbst@...hat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_bo.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index 35bb0bb3fe61..126b3c6e12f9 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -822,6 +822,15 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict,
>  		if (ret == 0) {
>  			ret = nouveau_fence_new(chan, false, &fence);
>  			if (ret == 0) {
> +				/* TODO: figure out a better solution here
> +				 *
> +				 * wait on the fence here explicitly as going through
> +				 * ttm_bo_move_accel_cleanup somehow doesn't seem to do it.
> +				 *
> +				 * Without this the operation can timeout and we'll fallback to a
> +				 * software copy, which might take several minutes to finish.
> +				 */
> +				nouveau_fence_wait(fence, false, false);
>  				ret = ttm_bo_move_accel_cleanup(bo,
>  								&fence->base,
>  								evict, false,

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat