[PATCH] drm/atomic-helpers: remove legacy_cursor_update hacks
Melissa Wen
mwen at igalia.com
Mon Sep 26 15:06:59 UTC 2022
On 04/13, Daniel Vetter wrote:
> On Wed, 13 Apr 2022 at 01:36, Abhinav Kumar <quic_abhinavk at quicinc.com> wrote:
> >
> > Hi Daniel
> >
> > On 4/8/2022 9:04 PM, Abhinav Kumar wrote:
> > >
> > >
> > > On 4/7/2022 4:12 PM, Rob Clark wrote:
> > >> On Thu, Apr 7, 2022 at 3:59 PM Abhinav Kumar
> > >> <quic_abhinavk at quicinc.com> wrote:
> > >>>
> > >>> Hi Rob and Daniel
> > >>>
> > >>> On 4/7/2022 3:51 PM, Rob Clark wrote:
> > >>>> On Wed, Apr 6, 2022 at 6:27 PM Jessica Zhang
> > >>>> <quic_jesszhan at quicinc.com> wrote:
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> On 3/31/2022 8:20 AM, Daniel Vetter 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.
> > >>>>>>
> > >>>>>> v3: Paper over msm and i915 regression. The complete_all is the only
> > >>>>>> thing missing afaict.
> > >>>>>>
> > >>>>>> v4: Fixup i915 fixup ...
> > >>>>>>
> > >>>>>> References: https://bugzilla.kernel.org/show_bug.cgi?id=199425
> > >>>>>> References:
> > >>>>>> https://lore.kernel.org/all/20220221134155.125447-9-maxime@cerno.tech/
> > >>>>>>
> > >>>>>> References: https://bugzilla.kernel.org/show_bug.cgi?id=199425
> > >>>>>> Cc: Maxime Ripard <maxime at cerno.tech>
> > >>>>>> Tested-by: Maxime Ripard <maxime at cerno.tech>
> > >>>>>> Cc: mikita.lipski at amd.com
> > >>>>>> Cc: Michel Dänzer <michel at daenzer.net>
> > >>>>>> Cc: harry.wentland at amd.com
> > >>>>>> Cc: Rob Clark <robdclark at gmail.com>
> > >>>>>
> > >>>>> Hey Rob,
> > >>>>>
> > >>>>> I saw your tested-by and reviewed-by tags on Patchwork. Just curious,
> > >>>>> what device did you test on?
> > >>>>
> > >>>> I was testing on strongbad.. v5.18-rc1 + patches (notably, revert
> > >>>> 80253168dbfd ("drm: of: Lookup if child node has panel or bridge")
> > >>>>
> > >>>> I think the display setup shouldn't be significantly different than
> > >>>> limozeen (ie. it's an eDP panel). But I didn't do much start/stop
> > >>>> ui.. I was mostly looking to make sure cursor movements weren't
> > >>>> causing fps drops ;-)
> > >>>>
> > >>>> BR,
> > >>>> -R
> > >>>
> > >>> start ui/ stop ui is a basic operation for us to use IGT on msm-next.
> > >>> So we cannot let that break.
> > >>>
> > >>> I think we need to check whats causing this splat.
> > >>>
> > >>> Can we hold back this change till then?
> > >>
> > >> Can you reproduce on v5.18-rc1 (plus 80253168dbfd)? I'm running a
> > >> loop of stop ui / start ui and hasn't triggered a splat yet.
> > >>
> > >> Otherwise maybe you can addr2line to figure out where it crashed?
> > >>
> > >> BR,
> > >> -R
> > >
> > > So this is not a crash. Its a warning splat coming from
> > >
> > > https://gitlab.freedesktop.org/drm/msm/-/blob/msm-next/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c#L785
> > >
> > >
> > > Looks like the complete_commit() which should signal the event has not
> > > happened before the next cursor commit.
> > >
> > > Somehow this change is affecting the flow to miss the event signaling
> > > that the event is done.
> > >
> > > We tried a couple of approaches but couldnt still fix the warning.
> > >
> > > Will continue to check further next week.
> > >
> > >>
> > >>> Thanks
> > >>>
> > >>> Abhinav
> >
> > After checking this more this week, I think the current patch needs to
> > be changed a bit.
> >
> > So, here you are removing the complete_all part and leaving that to the
> > individual drivers, which is fine.
> >
> > But, you are also removing the continue part which I think seems
> > incorrect and causing these warnings for MSM driver.
> >
> > @@ -2135,12 +2128,6 @@ 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;
> > - }
> > -
> >
> > Thats because MSM driver thinks that if the previous crtc_state->event
> > was not consumed, then something went wrong and throws a warning.
> >
> > if (!new_crtc_state->event) {
> > commit->event = kzalloc(sizeof(*commit->event),
> > GFP_KERNEL);
> > if (!commit->event)
> > return -ENOMEM;
> >
> > new_crtc_state->event = commit->event;
> > }
> >
> > But for a cursor update, we should not or need not populate the event at
> > all because it is async.
> >
> > So i think we should still keep the continue, rest of the patch is fine.
> >
> > @@ -2128,6 +2128,9 @@ int drm_atomic_helper_setup_commit(struct
> > drm_atomic_state *state,
> > continue;
> > }
> >
> > + if (state->legacy_cursor_update)
> > + continue;
> > +
> >
> > Let me know your comments.
>
> Thanks a lot for your excellent analysis. I need to think this through
> some more and figure out what exactly we should be doing.
> -Daniel
Hi,
I was checking drm-misc-next state using a HDMI 4k in a Raspberry Pi 4
and I see part of the screen being corrupted by moving the cursor to the
corners and bottom area - using drm-misc-next (a70abdd994c) + x11 +
`disable_overscan=1`. So, Maxime pointed this patch to me and, indeed,
it solves the issue.
I wonder if there is any chance of having this (or a next version)
upstream.
Thanks,
Melissa
>
> > Thanks
> >
> > Abhinav
> > >>>>
> > >>>>> I'm hitting several instances of this error when doing a start/stop ui
> > >>>>> on Lazor Chromebook with this patch:
> > >>>>>
> > >>>>> [ 3092.608322] CPU: 2 PID: 18579 Comm: DrmThread Tainted: G W
> > >>>>> 5.17.0-rc2-lockdep-00089-g7f17ab7bf567 #155
> > >>>>> e5912cd286513b064a82a38938b3fdef86b079aa
> > >>>>> [ 3092.622880] Hardware name: Google Lazor Limozeen without
> > >>>>> Touchscreen
> > >>>>> (rev4) (DT)
> > >>>>> [ 3092.630492] pstate: 80400009 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS
> > >>>>> BTYPE=--)
> > >>>>> [ 3092.637664] pc : dpu_crtc_atomic_flush+0x9c/0x144
> > >>>>> [ 3092.642523] lr : dpu_crtc_atomic_flush+0x60/0x144
> > >>>>> [ 3092.647379] sp : ffffffc00c1e3760
> > >>>>> [ 3092.650805] x29: ffffffc00c1e3760 x28: ffffff80985dd800 x27:
> > >>>>> 0000000000000425
> > >>>>> [ 3092.658164] x26: ffffff80985dc500 x25: ffffff80985ddc00 x24:
> > >>>>> ffffffdf8ae3b6f0
> > >>>>> [ 3092.665522] x23: 0000000000000000 x22: 0000000000000000 x21:
> > >>>>> ffffff809b82da00
> > >>>>> [ 3092.672890] x20: ffffff80840e1000 x19: ffffff80840e2000 x18:
> > >>>>> 0000000000001000
> > >>>>> [ 3092.680255] x17: 0000000000000400 x16: 0000000000000100 x15:
> > >>>>> 000000000000003b
> > >>>>> [ 3092.687622] x14: 0000000000000000 x13: 0000000000000002 x12:
> > >>>>> 0000000000000003
> > >>>>> [ 3092.694979] x11: ffffff8084009000 x10: 0000000000000040 x9 :
> > >>>>> 0000000000000040
> > >>>>> [ 3092.702340] x8 : 0000000000000300 x7 : 000000000000000c x6 :
> > >>>>> 0000000000000004
> > >>>>> [ 3092.709698] x5 : 0000000000000320 x4 : 0000000000000018 x3 :
> > >>>>> 0000000000000000
> > >>>>> [ 3092.717056] x2 : 0000000000000000 x1 : 7bfb38b2a3a89800 x0 :
> > >>>>> ffffff809a1eb300
> > >>>>> [ 3092.724424] Call trace:
> > >>>>> [ 3092.726958] dpu_crtc_atomic_flush+0x9c/0x144
> > >>>>> [ 3092.731463] drm_atomic_helper_commit_planes+0x1bc/0x1c4
> > >>>>> [ 3092.736944] msm_atomic_commit_tail+0x23c/0x3e0
> > >>>>> [ 3092.741627] commit_tail+0x7c/0xfc
> > >>>>> [ 3092.745145] drm_atomic_helper_commit+0x158/0x15c
> > >>>>> [ 3092.749998] drm_atomic_commit+0x60/0x74
> > >>>>> [ 3092.754055] drm_atomic_helper_update_plane+0x100/0x110
> > >>>>> [ 3092.759449] __setplane_atomic+0x11c/0x120
> > >>>>> [ 3092.763685] drm_mode_cursor_universal+0x188/0x22c
> > >>>>> [ 3092.768633] drm_mode_cursor_common+0x120/0x1f8
> > >>>>> [ 3092.773310] drm_mode_cursor_ioctl+0x68/0x8c
> > >>>>> [ 3092.777721] drm_ioctl_kernel+0xe8/0x168
> > >>>>> [ 3092.781770] drm_ioctl+0x320/0x370
> > >>>>> [ 3092.785289] drm_compat_ioctl+0x40/0xdc
> > >>>>> [ 3092.789257] __arm64_compat_sys_ioctl+0xe0/0x150
> > >>>>> [ 3092.794030] invoke_syscall+0x80/0x114
> > >>>>> [ 3092.797905] el0_svc_common.constprop.3+0xc4/0xf8
> > >>>>> [ 3092.802765] do_el0_svc_compat+0x2c/0x54
> > >>>>> [ 3092.806811] el0_svc_compat+0x4c/0xe4
> > >>>>> [ 3092.810598] el0t_32_sync_handler+0xc4/0xf4
> > >>>>> [ 3092.814914] el0t_32_sync+0x174/0x178
> > >>>>> [ 3092.818701] irq event stamp: 55940
> > >>>>> [ 3092.822217] hardirqs last enabled at (55939): [<ffffffdf8ad617a4>]
> > >>>>> exit_to_kernel_mode+0x10c/0x11c
> > >>>>> [ 3092.831523] hardirqs last disabled at (55940): [<ffffffdf8ad62728>]
> > >>>>> el1_dbg+0x28/0x70
> > >>>>> [ 3092.839577] softirqs last enabled at (55938): [<ffffffdf8a2103a8>]
> > >>>>> __do_softirq+0x1e8/0x480
> > >>>>> [ 3092.848256] softirqs last disabled at (55923): [<ffffffdf8a28d668>]
> > >>>>> __irq_exit_rcu+0xdc/0x140
> > >>>>> [ 3092.857022] ---[ end trace 0000000000000000 ]---
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> Thanks,
> > >>>>>
> > >>>>> Jessica Zhang
> > >>>>>
> > >>>>>> Cc: "Kazlauskas, Nicholas" <nicholas.kazlauskas at amd.com>
> > >>>>>> Cc: Dmitry Osipenko <dmitry.osipenko at collabora.com>
> > >>>>>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> > >>>>>> ---
> > >>>>>> drivers/gpu/drm/drm_atomic_helper.c | 13 -------------
> > >>>>>> drivers/gpu/drm/i915/display/intel_display.c | 14 ++++++++++++++
> > >>>>>> drivers/gpu/drm/msm/msm_atomic.c | 2 ++
> > >>>>>> 3 files changed, 16 insertions(+), 13 deletions(-)
> > >>>>>>
> > >>>>>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> > >>>>>> b/drivers/gpu/drm/drm_atomic_helper.c
> > >>>>>> index 9603193d2fa1..a2899af82b4a 100644
> > >>>>>> --- a/drivers/gpu/drm/drm_atomic_helper.c
> > >>>>>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > >>>>>> @@ -1498,13 +1498,6 @@ drm_atomic_helper_wait_for_vblanks(struct
> > >>>>>> drm_device *dev,
> > >>>>>> int i, ret;
> > >>>>>> unsigned int 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;
> > >>>>>> @@ -2135,12 +2128,6 @@ 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);
> > >>>>>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > >>>>>> b/drivers/gpu/drm/i915/display/intel_display.c
> > >>>>>> index d2abe0e430bf..6ca5a6e7703b 100644
> > >>>>>> --- a/drivers/gpu/drm/i915/display/intel_display.c
> > >>>>>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > >>>>>> @@ -8799,6 +8799,20 @@ static int intel_atomic_commit(struct
> > >>>>>> drm_device *dev,
> > >>>>>> intel_runtime_pm_put(&dev_priv->runtime_pm,
> > >>>>>> state->wakeref);
> > >>>>>> return ret;
> > >>>>>> }
> > >>>>>> +
> > >>>>>> + /*
> > >>>>>> + * FIXME: Cut over to (async) commit helpers instead of
> > >>>>>> hand-rolling
> > >>>>>> + * everything.
> > >>>>>> + */
> > >>>>>> + if (state->base.legacy_cursor_update) {
> > >>>>>> + struct intel_crtc_state *new_crtc_state;
> > >>>>>> + struct intel_crtc *crtc;
> > >>>>>> + int i;
> > >>>>>> +
> > >>>>>> + for_each_new_intel_crtc_in_state(state, crtc,
> > >>>>>> new_crtc_state, i)
> > >>>>>> +
> > >>>>>> complete_all(&new_crtc_state->uapi.commit->flip_done);
> > >>>>>> + }
> > >>>>>> +
> > >>>>>> intel_shared_dpll_swap_state(state);
> > >>>>>> intel_atomic_track_fbs(state);
> > >>>>>>
> > >>>>>> diff --git a/drivers/gpu/drm/msm/msm_atomic.c
> > >>>>>> b/drivers/gpu/drm/msm/msm_atomic.c
> > >>>>>> index 1686fbb611fd..b3cfabebe5d6 100644
> > >>>>>> --- a/drivers/gpu/drm/msm/msm_atomic.c
> > >>>>>> +++ b/drivers/gpu/drm/msm/msm_atomic.c
> > >>>>>> @@ -222,6 +222,8 @@ 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->commit->flip_done);
> > >>>>>> +
> > >>>>>> /*
> > >>>>>> * Start timer if we don't already have an update
> > >>>>>> pending
> > >>>>>> * on this crtc:
> > >>>>>> --
> > >>>>>> 2.34.1
> > >>>>>>
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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