Re: Mutter failing to handle failed mode sets

[Michael Thayer <michael thayer oracle com>]

Hello Jonas,

06.09.2018 16:01, Jonas Ådahl wrote:
> Mutter should already handle falling back on plain mode sets if flipping
> failed.

Not sure if I was quite clear.  We do not support flipping at all, and
it is the mode set which fails.  It looks to me (am I right?) like
Mutter does not handle that.  In my case continuing to use the old mode
would make sense, but I don't know whether this would make sense in
other situations.  On the other hand, my case is presumably the only
known one where it is a problem at all.

> I'd suggest opening a issue (on
> https://gitlab.gnome.org/GNOME/mutter/issues/new) with reproduction
> steps etc. A question however
> (to answer in the reported issue) is why a subsequent mode flip fixes
> things if the first one failed to too little video RAM?

What fixes it is triggering another mode switch to a smaller mode.  It
is quite easy to send hotplug events with any given preferred size in
VirtualBox.

Thanks and regards
Michael

> Jonas
>
> On Thu, Sep 06, 2018 at 11:43:46AM +0200, Michael Thayer via gnome-shell-list wrote:
> > Hello,
> >
> > Hans (on CC) asked me to file a bug for this, but I wanted to ask on the
> > mailing list first in case I am misreading the code.  We have been
> > looking at a problem where GNOME Shell on a VirtualBox guest with the
> > Additions video driver becomes unusable when a mode set operation fails
> > (due to too little video RAM allocated).  A further successful mode set
> > cures things.  It seems to me that this is due to Mutter failing to
> > check the return value of meta_gpu_kms_flip_crtc() and assuming that the
> > mode set succeeded.  Does that sound likely?  In case it is helpful to
> > know, the video driver still does not support either atomic or page flips.
> >
> > Regards
> > Michael
> > -- 
> > Michael Thayer | VirtualBox engineer
> > ORACLE Deutschland B.V. & Co. KG | Werkstr. 24 | D-71384 Weinstadt
> >
> > ORACLE Deutschland B.V. & Co. KG
> > Hauptverwaltung: Riesstraße 25, D-80992 München
> > Registergericht: Amtsgericht München, HRA 95603
> >
> > Komplementärin: ORACLE Deutschland Verwaltung B.V.
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>
> > pub   rsa3072 2018-06-26 [SC] [expires: 2019-06-26]
> >       00474F6447A79D8998B7542123F0CF2E68CC7371
> > uid           Michael Thayer <michael thayer oracle com>
> > sub   rsa3072 2018-06-26 [E] [expires: 2019-06-26]
>
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-- 
Michael Thayer | VirtualBox engineer
ORACLE Deutschland B.V. & Co. KG | Werkstr. 24 | D-71384 Weinstadt

ORACLE Deutschland B.V. & Co. KG
Hauptverwaltung: Riesstraße 25, D-80992 München
Registergericht: Amtsgericht München, HRA 95603

Komplementärin: ORACLE Deutschland Verwaltung B.V.
Hertogswetering 163/167, 3543 AS Utrecht, Niederlande
Handelsregister der Handelskammer Midden-Nederland, Nr. 30143697
Geschäftsführer: Alexander van der Ven, Jan Schultheiss, Val Maher

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