Comment 4 for bug 1715356

Disagree on 666. Just because udev does it, doesn't mean it is correct. E.G. dd if=/dev/zero of=/dev/kvm will blow up the system. kvm should only be accessible by the qemu group. It is possible to properly set permissions for qemu:

e.g.:
https://github.com/openstack/kolla-ansible/blob/master/ansible/roles/nova/templates/qemu.conf.j2#L10-L11