libvirt users - Sep 2021 - snapshot creation broken recently?

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,

  ?t?p?n

On Thu, Sep 09, 2021 at 02:33:25PM +0200, ?t?p?n N?mec
wrote:
> 
>   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?
Yes, auite likely related to the QEMU update as

  "pre-save failed: qxl"

is an error message that libvirt is getting back from QEMU.

There was a change in this code in qemu in 6.1.0, but that was
replacing an assert() with this graceful error message. So if
anything your older QEMU ought to have been crashing !

Anyway, I think you need to report this to the QEMU community.


Regards,
Daniel
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