[Spice-devel] Multiple monitors at 4K, in virt-manager?

[Victor Toso]

Hi,

On Mon, Mar 22, 2021 at 01:46:08PM +0000, Dr. Jennifer Nussbaum wrote:
> I hope it's OK to ask a basic question on the -devel list, but
> this is what was listed in the Support section....

Sure

> I'm using virt-manger, and its related suite of stuff, to run
> KVM/QEMU VM's on a Debian Bullseye host, which has two 4K
> monitors. I am unable to get dual-head working at all, and I
> can't get 4K resolution working in the way I'm apparently
> supposed to.

Can you share the vm's domain? virsh dumpxml $vm

> I have a Debian Bullseye guest, with spice-vdagent and the QXL
> video drivers installed in it. The Spice user manual suggests
> that multiple-monitor support is easy; you're supposed to use a
> Video QXL device and then everything should just work. But it
> doesn't. Even when I increase the video memory in the XML file
> (vgamem, I assume) to 64MB I am unable to get 4K on even a
> single monitor using Settings -> Display on the guest; it maxes
> out at some arbitrary-seeming thing a bit over 1980 x 1200. And
> regardless of resolution, I also do not have a second monitor
> available in the guest.

Are you accessing with virt-manager? I don't think there is
support for multi-monitor there? You should use virt-viewer or
remote-viewer instead.

> If I have a video device set to Virtio, then 4K works perfectly
> on the guest machine; if I go to Settings -> Display there, I
> can select 4096 x 2160, and I get lovely 4K video. However,
> dual-head does not work. If I try to edit the XML for the video
> device to 'heads="2"', there is no effect--at least, when I
> restart the guest and go to Settings -> Display, there isn't an
> option for selecting another monitor.  Could someone tell me
> what I'm supposed to be doing?  Thank you.

Just confirming, for Spice multi-monitor [0] in recent linux
guests, one qxl device is enough and you should set the heads to
2 (virsh edit $vm)

[0] https://www.spice-space.org/multiple-monitors.html

Cheers,
Victor
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