Re: [PATCH 2/2] drm/virtio: Recalculate ignore_damage_clips on every update

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Preexisting bug in vmwgfx: Plane state duplication permanently preserves ignore_damage_clips, disabling partial updates.
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commit 18671312bd2be6fe18c7092369d0bbfb67a39103
Author: Christian Hergert <christian@sourceandstack.com>

drm/virtio: Recalculate ignore_damage_clips on every update

Plane state duplication preserves ignore_damage_clips. Once fbdev sets
it for a dumb buffer, later updates using rendered resources continue to
ignore damage because the flag is never cleared.

Assign ignore_damage_clips on every atomic check so rendered resources
can use supplied damage after an earlier dumb-buffer update.

> diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
> index d9579a4b4714c..95ec688690d3a 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_plane.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
> @@ -119,8 +119,8 @@ static int virtio_gpu_plane_atomic_check(struct drm_plane *plane,
>  	 * so preserve userspace's accumulated per-buffer damage for those.
>  	 */
>  	bo = gem_to_virtio_gpu_obj(new_plane_state->fb->obj[0]);
> -	if (old_plane_state->fb != new_plane_state->fb && bo->dumb)
> -		new_plane_state->ignore_damage_clips = true;
> +	new_plane_state->ignore_damage_clips =
> +		old_plane_state->fb != new_plane_state->fb && bo->dumb;

[Severity: High]
This is a pre-existing issue, but does the same problem exist in vmwgfx?

Looking at vmw_du_primary_plane_atomic_check() in
drivers/gpu/drm/vmwgfx/vmwgfx_kms.c:

	if (old_fb != new_fb)
		new_state->ignore_damage_clips = true;

When old_fb == new_fb, it fails to clear the flag.

Once the flag is set to true during a page flip, won't it remain permanently
true across future state duplications?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260903211914.1109100-1-lyude@redhat.com?part=2