[libvirt] [PATCH v2] qemu: map "virtio" video model to "virt" machtype correctly (arm/aarch64)

[Pavel Hrdina]

On Fri, Sep 16, 2016 at 03:44:34PM +0200, Andrea Bolognani wrote:
> On Fri, 2016-09-16 at 15:20 +0200, Pavel Hrdina wrote:
> > > There is something I wanted to clarify with Laszlo: is
> > > virtio-gpu-pci ever going to be usable on other architectures
> > > such as x86_64? Maybe it already is? Because if that's the
> > > case, we'll want to be able to choose between virtio-vga and
> > > virtio-gpu-pci.
> > > 
> > > One solution would be to keep mapping model='virtio' to
> > > virtio-vga and create a new model='virtio-gpu' that maps to
> > > virtio-gpu-pci, then forbid aarch64 mach-virt guests to use
> > > model='virtio'. Or something like that, I'm not married to
> > > the idea, I just think it's something we should definitely
> > > think about before this ends up in a release.
> > 
> > I have some patches in my TODO branch that will rewrite the video
> > device code. virtio-gpu-pci is usable also on other architectures
> > but it lacks the VGA compatibility mode.  In libvirt all primary
> > video devices for x86 architecture have VGA mode.  Currently we
> > allow only QXL to be used as secondary video device and now with
> > the virtio-gpu-pci it could be also used as secondary video device.
> > 
> > The solution would be simple, there is no need to add a new video
> > model 'virtio-gpu', we will use the existing model 'virtio', but
> > depending on architecture and also whether it's primary or
> > secondary video device we will use appropriate device.
> > We already do this for QXL.
> 
> I don't know much about video devices, so forgive me if I'm
> asking silly questions, but what is preventing you (on x86)
> from having virtio-vga as secondary video device? Or
> virtio-gpu-pci as primary video device?

You can use both as primary or secondary but it doesn't make
much sense to use only video device without VGA support on x86.
See Laszlo's explanation [1].

[1] <https://www.redhat.com/archives/libvir-list/2016-September/msg00626.html>

Pavel