Comment 6 for bug 1564831

Regarding issue 2), this is most probably due to the cpu mode setting:
  <cpu mode='host-model'>
    <model fallback='allow'/>
    <topology sockets='1' cores='1' threads='1'/>
  </cpu>

The nova.conf needs the setting "cpu_mode = none" in order to not have it set to 'host-model'.
This setting has not been working on s390x - this is a statement as of Mitaka and libvirt 1.2.21 at least