linux-kernel - Re: Re: [PATCH] drm/atomic-helpers: remove legacy_cursor

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Message-ID: <vyh5wg2ltmrtqw2mhtyj2lii6i4eccrjjlynzpfg7x63tkrav6@cxbz3sasvjjm>
Date: Sun, 28 Jan 2024 10:24:02 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>, 
	"manasi.d.navare@...el.com" <manasi.d.navare@...el.com>, 
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"michel@...nzer.net" <michel@...nzer.net>, 
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>, "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>, 
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>, "mikita.lipski@....com" <mikita.lipski@....com>, 
	"dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>, "tzimmermann@...e.de" <tzimmermann@...e.de>, 
	"daniel.vetter@...el.com" <daniel.vetter@...el.com>, "nicholas.kazlauskas@....com" <nicholas.kazlauskas@....com>, 
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>, "quic_abhinavk@...cinc.com" <quic_abhinavk@...cinc.com>, 
	Project_Global_Chrome_Upstream_Group <Project_Global_Chrome_Upstream_Group@...iatek.com>, "lucas.demarchi@...el.com" <lucas.demarchi@...el.com>, 
	"sean@...rly.run" <sean@...rly.run>, "matthias.bgg@...il.com" <matthias.bgg@...il.com>, 
	"dmitry.osipenko@...labora.com" <dmitry.osipenko@...labora.com>, "fshao@...omium.org" <fshao@...omium.org>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "jani.nikula@...el.com" <jani.nikula@...el.com>, 
	"angelogioacchino.delregno@...labora.com" <angelogioacchino.delregno@...labora.com>, 
	"freedreno@...ts.freedesktop.org" <freedreno@...ts.freedesktop.org>
Subject: Re: Re: [PATCH] drm/atomic-helpers: remove legacy_cursor_update hacks

On Thu, Jan 25, 2024 at 07:17:21PM +0100, Daniel Vetter wrote:
> On Tue, Jan 23, 2024 at 06:09:05AM +0000, Jason-JH Lin (林睿祥) wrote:
> > Hi Maxime, Daniel,
> > 
> > We encountered similar issue with mediatek SoCs.
> > 
> > We have found that in drm_atomic_helper_commit_rpm(), when disabling
> > the cursor plane, the old_state->legacy_cursor_update in
> > drm_atomic_wait_for_vblank() is set to true.
> > As the result, we are not actually waiting for a vlbank to wait for our
> > hardware to close the cursor plane. Subsequently, the execution
> > proceeds to drm_atomic_helper_cleanup_planes() to  free the cursor
> > buffer. This can lead to use-after-free issues with our hardware.
> > 
> > Could you please apply this patch to fix our problem?
> > Or are there any considerations for not applying this patch?
> 
> Mostly it needs someone to collect a pile of acks/tested-by and then land
> it.
> 
> I'd be _very_ happy if someone else can take care of that ...
> 
> There's also the potential issue that it might slow down some of the
> legacy X11 use-cases that really needed a non-blocking cursor, but I think
> all the drivers where this matters have switched over to the async plane
> update stuff meanwhile. So hopefully that's good.

I think there was also a regression with msm no one really figured out?

Maxime

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