'Checks if pv drivers are present for this instance. If it is
present but not reported, try to fake the info for live-migration.'

def _ensure_pv_driver_info_for_live_migration(self, instance, vm_ref):

    if self._pv_driver_version_reported(instance, vm_ref):
        return
    if self._pv_device_reported(instance, vm_ref):
        LOG.debug('PV    device    present    but    missing    pv    driver    info.    Attempting    to    insert    missing    info    in    xenstore.', instance=instance)
        self._write_fake_pv_version(instance, vm_ref)
    else:
        LOG.debug('Could    not    determine    the    presence    of    pv    device.    Skipping    inserting    pv    driver    info.', instance=instance)
