Comment 9 for bug 457716

The apparmor profile in Ubuntu works around the upstream bug, which lacks the proper functionality. Look in your /var/log/kern.log, you are probably trying to save the file outside of the allowed location. See /etc/apparmor.d/abstractions/libvirt-qemu for details.

Basically, you can write state files in your home directory if you own them. If this does not fit your workflow, please update /etc/apparmor.d/abstractions/libvirt-qemu for the location(s) you want to give write access until this functionality is properly implemented in libvirt itself.