From: Thomas Zimmermann <tzimmermann@suse.de>
To: syzbot <syzbot+91525b2bd4b5dff71619@syzkaller.appspotmail.com>,
airlied@linux.ie, christian.koenig@amd.com,
daniel.vetter@ffwll.ch, daniel.vetter@intel.com, daniel@ffwll.ch,
dri-devel@lists.freedesktop.org,
linaro-mm-sig-owner@lists.linaro.org,
linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org,
linux-media@vger.kernel.org, maarten.lankhorst@linux.intel.com,
melissa.srw@gmail.com, mripard@kernel.org,
sumit.semwal@linaro.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] WARNING in drm_gem_shmem_vm_open
Date: Fri, 20 Aug 2021 21:23:52 +0200 [thread overview]
Message-ID: <dc7ca5ae-afc1-f840-8dfc-3f2361cd4360@suse.de> (raw)
In-Reply-To: <00000000000047b52b05c9ff8d0b@google.com>
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Hi
Am 20.08.21 um 17:45 schrieb syzbot:
> syzbot has bisected this issue to:
Good bot!
>
> commit ea40d7857d5250e5400f38c69ef9e17321e9c4a2
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date: Fri Oct 9 23:21:56 2020 +0000
>
> drm/vkms: fbdev emulation support
Here's a guess.
GEM SHMEM + fbdev emulation requires that
(drm_mode_config.prefer_shadow_fbdev = true). Otherwise, deferred I/O
and SHMEM conflict over the use of page flags IIRC.
From a quick grep, vkms doesn't set prefer_shadow_fbdev and an alarming
amount of SHMEM-based drivers don't do either.
Best regards
Thomas
>
> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11c31d55300000
> start commit: 614cb2751d31 Merge tag 'trace-v5.14-rc6' of git://git.kern..
> git tree: upstream
> final oops: https://syzkaller.appspot.com/x/report.txt?x=13c31d55300000
> console output: https://syzkaller.appspot.com/x/log.txt?x=15c31d55300000
> kernel config: https://syzkaller.appspot.com/x/.config?x=96f0602203250753
> dashboard link: https://syzkaller.appspot.com/bug?extid=91525b2bd4b5dff71619
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=122bce0e300000
>
> Reported-by: syzbot+91525b2bd4b5dff71619@syzkaller.appspotmail.com
> Fixes: ea40d7857d52 ("drm/vkms: fbdev emulation support")
>
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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next prev parent reply other threads:[~2021-08-20 19:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-19 8:21 [syzbot] WARNING in drm_gem_shmem_vm_open syzbot
2021-08-20 15:45 ` syzbot
2021-08-20 19:23 ` Thomas Zimmermann [this message]
2021-08-20 19:33 ` Daniel Vetter
2022-01-31 7:50 ` syzbot
2022-05-12 13:10 ` Dmitry Vyukov
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