Dear Andreas,

of course, I can ...

On 12.11.2025 21:17, Andreas Messer wrote:
> Dear Ruediger,
>
> Am Thu, Nov 06, 2025 at 01:56:54PM +0100 schrieb H.-R. Oberhage:
>> The problem here most probably are the PV (paravirtualized) VMs.
>> There is no "spice" option available for it, to my dismay, so
>> I'm stuck with VNC as display device and the "video" is "xen".
>
> I experimented a bit with different display options here. For me
> VNC display worked at least with qemu. Can you post the output
> when starting a vm from cmd like so:
>
> $ virsh -d0 -c qemu:///system start devuan-daedalus
> start: domain(optdata): devuan-daedalus
> start: found option <domain>: devuan-daedalus
> start: <domain> trying as domain NAME
> error: Failed to start domain 'devuan-daedalus'
> error: internal error: process exited while connecting to monitor:
> 2025-11-12T20:10:32.687041Z qemu-system-x86_64: warning: This feature
> depends on other features that were not requested:
> CPUID.8000000AH:EDX.flushbyasid [bit 6]
> 2025-11-12T20:10:32.687042Z qemu-system-x86_64: warning: This feature
> depends on other features that were not requested:
> CPUID.8000000AH:EDX.pause-filter [bit 10]
> 2025-11-12T20:10:32.687044Z qemu-system-x86_64: warning: This feature
> depends on other features that were not requested:
> CPUID.8000000AH:EDX.pfthreshold [bit 12]
> 2025-11-12T20:10:32.687045Z qemu-system-x86_64: warning: This feature
> depends on other features that were not requested:
> CPUID.8000000AH:EDX.vgif [bit 16]
> 2025-11-12T20:10:32.695765Z qemu-system-x86_64: -device
> {"driver":"virtio-vga-gl","id":"video0","max_outputs":1,"bus":"pcie.0","addr":"0x1"}:
> The display backend does not have OpenGL support enabled
> It can be enabled with '-display BACKEND,gl=on' where BACKEND is the
> name of the display backend to use.
>
> (This was output with a intentionally bad config) I assume
> you have to use "xen:///system" instead for connect uri.

... do so, and yes, you're correct, it has to be a "-c xen:///system"
for me.
But you may be disappointed as to what happens then:

# virsh -d0 -c xen:///system start DevuanDev
start: domain(optdata): DevuanDev
start: found option <domain>: DevuanDev
start: <domain> trying as domain NAME
Domain 'DevuanDev' started

That's the total output. Or would you like it to "fail" to get more
debug information?

The "Dom0" is registered by qemu as:
root      2411     1  0 14:45 ?        00:00:00 
/usr/libexec/xen-qemu-system-i386 -xen-domid 0 -xen-attach -name dom0 
-nographic -M xenpv -daemonize -monitor none -serial none -parallel none 
-pidfile /run/qemu-dom0.pid

and the "running" VM is registered as:
root      3206     1  0 14:51 ?        00:00:00 
/usr/libexec/xen-qemu-system-i386 -xen-domid 2 -no-shutdown -chardev 
socket,id=libxl-cmd,path=/var/run/xen/qmp-libxl-2,server=on,wait=off 
-mon chardev=libxl-cmd,mode=control -chardev 
socket,id=libxenstat-cmd,path=/var/run/xen/qmp-libxenstat-2,server=on,wait=off 
-mon chardev=libxenstat-cmd,mode=control -nodefaults -no-user-config 
-xen-attach -name DevuanDev -vnc 127.0.0.1:1 -display none -machine 
xenpv -m 4096

and just "humming" there.

Doing a
# virt-viewer DevuanDev
results in a "normal" graphical window, just that it shows the
"This VM has no graphic display device."
message in it.

> I currently have no xen machine for further tests here,
> maybe I have to prepare it.

Well, if I can be of any help, I'm willing to "execute" whatever you
suggest on my machine.

> Best regards,
> Andreas

Thanks and all the best,
  Ruediger
-- 
Dr. H.-R. Oberhage
Mail: Univ. Duisburg-Essen    E-Mail: oberhage@???
       Fakultaet fuer Physik