snapshot creation broken recently?

[Štěpán Němec]

  Hello,

until very recently I had been happily creating snapshots of running VMs
(created using virt-install) simply with

  virsh --connect qemu:///system snapshot-create-as <domain-name> <snapshot-name>

Now when I try to do that I get the following error:

  Error creating snapshot: operation failed: Failed to take snapshot: pre-save failed: qxl

Same thing trying to create a snapshot from virt-manager (which also
used to work). Here's the full backtrace (as displayed in virt-manager):

Error: Error while writing VM state: Unknown error -1


Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 65, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/details/snapshots.py", line 237, in _do_create_snapshot
    self.vm.create_snapshot(xml)
  File "/usr/share/virt-manager/virtManager/object/domain.py", line 1124, in create_snapshot
    self._backend.snapshotCreateXML(xml, flags)
  File "/usr/lib/python3.9/site-packages/libvirt.py", line 3059, in snapshotCreateXML
    raise libvirtError('virDomainSnapshotCreateXML() failed')
libvirt.libvirtError: operation failed: Failed to take snapshot: pre-save failed: qxl
Error: Error while writing VM state: Unknown error -1

I am on Arch Linux (x86_64), using the distro packages. Checking my
pacman logs, might update of qemu-headless from 6.0.0 to 6.1.0 have
something to do with that?

(Since then, libvirt has also been updated from 7.6.0 to 7.7.0, but I
see no change WRT the problem described.)

I would appreciate any advice on how to further investigate and/or work
around the problem.

(I checked https://gitlab.com/libvirt/libvirt/-/issues and didn't find
anything that seemed related.)

  Thanks,

  Štěpán