Re: [REGRESSION] QXL display malfunction

[Thomas Zimmermann]

Am 01.07.24 um 12:02 schrieb Linux regression tracking (Thorsten Leemhuis):
> Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
> for once, to make this easily accessible to everyone.
>
> Thomas, was there some progress wrt to fixing below regression? I might
> have missed something, but from here it looks like this fall through the
> cracks.

Thanks for reminding.


> Makes me wonder if we should temporarily revert this for now to fix this
> for rc7 and ensure things get at least one week of testing before the final.
>
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> --
> Everything you wanna know about Linux kernel regression tracking:
> https://linux-regtracking.leemhuis.info/about/#tldr
> If I did something stupid, please tell me, as explained on that page.
>
> #regzbot poke
>
> On 14.06.24 15:45, Kaplan, David wrote:
> > [AMD Official Use Only - AMD Internal Distribution Only]
> >
> > > -----Original Message-----
> > > From: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > > Sent: Wednesday, June 12, 2024 9:26 AM
> > > To: Linux regressions mailing list <regressions@xxxxxxxxxxxxxxx>
> > > Cc: Petkov, Borislav <Borislav.Petkov@xxxxxxx>;
> > > zack.rusin@xxxxxxxxxxxx; dmitry.osipenko@xxxxxxxxxxxxx; Kaplan, David
> > > <David.Kaplan@xxxxxxx>; Koenig, Christian <Christian.Koenig@xxxxxxx>;
> > > Dave Airlie <airlied@xxxxxxxxxx>; Maarten Lankhorst
> > > <maarten.lankhorst@xxxxxxxxxxxxxxx>; Maxime Ripard
> > > <mripard@xxxxxxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>; ML dri-devel
> > > <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; spice-devel@xxxxxxxxxxxxxxxxxxxxx;
> > > virtualization@xxxxxxxxxxxxxxx
> > > Subject: Re: [REGRESSION] QXL display malfunction
> > >
> > > Caution: This message originated from an External Source. Use proper
> > > caution when opening attachments, clicking links, or responding.
> > >
> > >
> > > Hi
> > >
> > > Am 12.06.24 um 14:41 schrieb Linux regression tracking (Thorsten Leemhuis):
> > > > [CCing a few more people and lists that get_maintainers pointed out
> > > > for qxl]
> > > >
> > > > Hi, Thorsten here, the Linux kernel's regression tracker. Top-posting
> > > > for once, to make this easily accessible to everyone.
> > > >
> > > > Thomas, from here it looks like this report that apparently is caused
> > > > by a change of yours that went into 6.10-rc1 (b33651a5c98dbd
> > > > ("drm/qxl: Do not pin buffer objects for vmap")) fell through the
> > > > cracks. Or was progress made to resolve this and I just missed this?
> > > >
> > > > Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker'
> > > > hat)
> > > > --
> > > > Everything you wanna know about Linux kernel regression tracking:
> > > > https://linux-regtracking.leemhuis.info/about/#tldr
> > > > If I did something stupid, please tell me, as explained on that page.
> > > >
> > > > #regzbot poke
> > > >
> > > >
> > > > On 03.06.24 04:29, Kaplan, David wrote:
> > > > > > -----Original Message-----
> > > > > > From: Kaplan, David
> > > > > > Sent: Sunday, June 2, 2024 9:25 PM
> > > > > > To: tzimmermann@xxxxxxx; dmitry.osipenko@xxxxxxxxxxxxx; Koenig,
> > > > > > Christian <Christian.Koenig@xxxxxxx>; zach.rusin@xxxxxxxxxxxx
> > > > > > Cc: Petkov, Borislav <Borislav.Petkov@xxxxxxx>;
> > > > > > regressions@xxxxxxxxxxxxxx
> > > > > > Subject: [REGRESSION] QXL display malfunction
> > > > > >
> > > > > > Hi,
> > > > > >
> > > > > > I am running an Ubuntu 19.10 VM with a tip kernel using QXL video
> > > > > > and I've observed the VM graphics often malfunction after boot,
> > > > > > sometimes failing to load the Ubuntu desktop or even immediately
> > > shutting the guest down.
> > > > > > When it does load, the guest dmesg log often contains errors like
> > > > > >
> > > > > > [    4.303586] [drm:drm_atomic_helper_commit_planes] *ERROR* head
> > > 1
> > > > > > wrong: 65376256x16777216+0+0
> > > > > > [    4.586883] [drm:drm_atomic_helper_commit_planes] *ERROR* head
> > > 1
> > > > > > wrong: 65376256x16777216+0+0
> > > > > > [    4.904036] [drm:drm_atomic_helper_commit_planes] *ERROR* head
> > > 1
> > > > > > wrong: 65335296x16777216+0+0
> > > I don't see how these messages are related. Did they already appear before
> > > the broken commit was there?
> > No, I did not observe them prior to the broken commit.
> >
> > > > > > [    5.374347] [drm:qxl_release_from_id_locked] *ERROR* failed to find
> > > id in
> > > > > > release_idr
> > > Is there only one such message in the log? Or multiple/frequent ones.
> > I would usually only see one.
> >
> > > Could you provide a stack trace of what happens before?
> > Here's the top of a backtrace when the error occurs:
> > #0  qxl_release_from_id_locked (qdev=qdev@entry=0xffff88810126e000, id=id@entry=262151)
> >      at drivers/gpu/drm/qxl/qxl_release.c:373
> > #1  0xffffffff819f5b6a in qxl_garbage_collect (qdev=0xffff88810126e000)
> >      at drivers/gpu/drm/qxl/qxl_cmd.c:222
> > #2  0xffffffff810e3aa8 in process_one_work (worker=worker@entry=0xffff888101680300,
> >      work=0xffff88810126f340) at kernel/workqueue.c:3231
> > #3  0xffffffff810e6281 in process_scheduled_works (worker=<optimized out>)
> >      at kernel/workqueue.c:3312
> > #4  worker_thread (__worker=0xffff888101680300) at kernel/workqueue.c:3393
> >
> > > We sometimes draw into the buffer object from the CPU. For accessing the
> > > buffer object's pages from the CPU, only a vmap operation should be
> > > necessary. It appears as if qxl also requires a pin. My guess is that the pin
> > > inserts the buffer-object's host-side pages and the code around
> > > qxl_release_from_id_locked() appears to be garbage-collecting them.
> > > Hence without the pin, the GC complains about inconsistent state.
> > > > > > I bisected the issue down to "drm/qxl: Do not pin buffer objects for
> > > vmap"
> > > > > > (b33651a5c98dbd5a919219d8c129d0674ef74299).
> > > Thanks for bisecting. Does it work if you revert that commit?
> > Yes
> >
> > Thanks --David Kaplan

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)