[Intel-gfx] [PATCH 1/3] drm/atomic-helpers: remove legacy_cursor_update hacks

[Rob Clark]

On Wed, Oct 21, 2020 at 9:32 AM Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>
> The stuff never really worked, and leads to lots of fun because it
> out-of-order frees atomic states. Which upsets KASAN, among other
> things.
>
> For async updates we now have a more solid solution with the
> ->atomic_async_check and ->atomic_async_commit hooks. Support for that
> for msm and vc4 landed. nouveau and i915 have their own commit
> routines, doing something similar.
>
> For everyone else it's probably better to remove the use-after-free
> bug, and encourage folks to use the async support instead. The
> affected drivers which register a legacy cursor plane and don't either
> use the new async stuff or their own commit routine are: amdgpu,
> atmel, mediatek, qxl, rockchip, sti, sun4i, tegra, virtio, and vmwgfx.
>
> Inspired by an amdgpu bug report.
>
> v2: Drop RFC, I think with amdgpu converted over to use
> atomic_async_check/commit done in
>
> commit 674e78acae0dfb4beb56132e41cbae5b60f7d662
> Author: Nicholas Kazlauskas <nicholas.kazlauskas at amd.com>
> Date:   Wed Dec 5 14:59:07 2018 -0500
>
>     drm/amd/display: Add fast path for cursor plane updates
>
> we don't have any driver anymore where we have userspace expecting
> solid legacy cursor support _and_ they are using the atomic helpers in
> their fully glory. So we can retire this.
>
> References: https://bugzilla.kernel.org/show_bug.cgi?id=199425
> Cc: mikita.lipski at amd.com
> Cc: Michel Dänzer <michel at daenzer.net>
> Cc: harry.wentland at amd.com
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

This *completely* destroys fps when there is cursor movement, it would
be a pretty bad regression, so nak

BR,
-R

> ---
>  drivers/gpu/drm/drm_atomic_helper.c | 13 -------------
>  1 file changed, 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index a7bcb4b4586c..549a31e6042c 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -1481,13 +1481,6 @@ drm_atomic_helper_wait_for_vblanks(struct drm_device *dev,
>         int i, ret;
>         unsigned crtc_mask = 0;
>
> -        /*
> -         * Legacy cursor ioctls are completely unsynced, and userspace
> -         * relies on that (by doing tons of cursor updates).
> -         */
> -       if (old_state->legacy_cursor_update)
> -               return;
> -
>         for_each_oldnew_crtc_in_state(old_state, crtc, old_crtc_state, new_crtc_state, i) {
>                 if (!new_crtc_state->active)
>                         continue;
> @@ -2106,12 +2099,6 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
>                         continue;
>                 }
>
> -               /* Legacy cursor updates are fully unsynced. */
> -               if (state->legacy_cursor_update) {
> -                       complete_all(&commit->flip_done);
> -                       continue;
> -               }
> -
>                 if (!new_crtc_state->event) {
>                         commit->event = kzalloc(sizeof(*commit->event),
>                                                 GFP_KERNEL);
> --
> 2.28.0
>
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx