Comment 8 for bug 517714

flolle, please do not disable all of the profiles. This is not needed and there are many profiles in place that are not causing the problem.

To workaround this, you can edit qemu.conf as suggested (and restart libvirtd), or simply temporarily disable the apparmor profile until a reboot with:
$ sudo apparmor_parser -R /etc/apparmor.d/usr.sbin.libvirtd