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

[Daniel Vetter]

On Thu, Oct 22, 2020 at 7:22 PM Rob Clark <robdclark at gmail.com> wrote:
>
> On Thu, Oct 22, 2020 at 10:02 AM Rob Clark <robdclark at gmail.com> wrote:
> >
> > 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
>
> Which I *guess* is due to dpu not wiring up the plane->async_* funcs,
> effectively making cursor updates synchronous.. but it will take some
> time to sort out :-(

Does something like the below (not even compile tested) get dpu back in order?

diff --git a/drivers/gpu/drm/msm/msm_atomic.c b/drivers/gpu/drm/msm/msm_atomic.c
index 561bfa48841c..ec8b4f74da49 100644
--- a/drivers/gpu/drm/msm/msm_atomic.c
+++ b/drivers/gpu/drm/msm/msm_atomic.c
@@ -215,6 +215,8 @@ void msm_atomic_commit_tail(struct drm_atomic_state *state)
               /* async updates are limited to single-crtc updates: */
               WARN_ON(crtc_mask != drm_crtc_mask(async_crtc));

+               complete_all(async_crtc->state->flip_done);
+
               /*
                * Start timer if we don't already have an update pending
                * on this crtc:

That way we could perhaps still move ahead with removing the hacks
from shared helpers, and msm-dpu can keep doing what it does. The
other hunk is in a function that dpu code doesn't even use, so can't
see how that would change anything.
-Daniel

>
> > 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



-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch