Re: Wondering about cirris and stdvga

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Pasi Kärkkäinen [mailto:pasik@iki.fi]
> Sent: 19 November 2016 10:57
> To: Dario Faggioli <dario.faggioli@citrix.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>; Paul Durrant
> <Paul.Durrant@citrix.com>; Anthony Perard <anthony.perard@citrix.com>;
> xen-devel <xen-devel@lists.xenproject.org>; Stefano Stabellini
> <sstabellini@kernel.org>; Ian Jackson <Ian.Jackson@citrix.com>; Roger Pau
> Monne <roger.pau@citrix.com>
> Subject: Re: [Xen-devel] Wondering about cirris and stdvga
> 
> On Fri, Nov 18, 2016 at 07:04:15PM +0100, Dario Faggioli wrote:
> > Sending again, this time, with Anthony's and xen-devel address spelled
> > right. Sorry!! :-(
> > -------------------------------------------
> > Hello to you, various pseudo-random people,
> >
> > It's not my field of expertise, so bear with me, at least a little bit
> > (and, Konrad, you help me, or there will be consequences! :-D)
> >
> > So, I and Konrad recently discovered --while testing the about to be
> > released Fedora 25 as a Xen guest-- that the Cirrus emulated graphic
> > card that we consume from QEMU for HVM guests is broken on Wayland.
> >
> > We just discovered it because Fedora 25 uses Wayland by default, but it
> > appears not to be something new:
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=1227770
> >
> > And at least from what we see in that bugreport, not much has happened
> > so far.
> >
> > Using "vga='stdvga'" in the config file, or even "vga='qxl'" make
> > things work again. Disabling Wayland in the guest also works (i.e., if
> > not using Wayland, Cirrus is ok). And that's what made us think that
> > it's probably a Wayland issue.
> >
> > I've tried the same on KVM, and the situation is identical
> > (Cirrus+Wayland=breaks, whatever-else+Wayland=works,
> > Cirrus+Xorg=works).
> >
> > I've also read around that these days, e.g., stdvga is at least as good
> > as cirrus, performance wise, that cirrus is broken and impossible to
> > fix (because it is the hardware that it's emulating that was broken),
> > that stdvga enables better screen resolution in guests, etc.
> >
> > I'm not sure about these claims, in particular the performance one, is
> > probably pretty hard to verify. And as I said, it's not my field.
> >
> > Still I thought it could be worthwhile to at least bring this up:
> > should we start to consider changing the default from cirrus to stdvga
> > (or something else)?
> >
> 
> There's multiple things here..
> 
> 1) Yes, +1, let's change the Xen HVM default to "stdvga".
> 

In general std-vga also gets a +1 from me, but I have recently found that a Windows Server 2008 guest does not boot (ar at least the display freezes on boot) when using std-vga with QEMU trad but everything is fine with Cirrus... so probably worth making the default dependent on which QEMU is being used. Never had any issues with std-vga on upstream QEMU.

  Paul

> 2) It'd good to create an upstream Wayland bugreport and investigate more
> about why cirrus is broken with Wayland.
> 
> 3) It'd be good to have Xen HVM with "qxl" tested by OSStest aswell..
> 
> 
> > Thanks for your time and Regards,
> > Dario
> 
> 
> Thanks,
> 
> -- Pasi


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