'Return VBD refs for all Nova/Cinder volumes.'

def _get_all_volume_vbd_refs(self, vm_ref):

    vbd_refs = self._session.VM.get_VBDs(vm_ref)
    for vbd_ref in vbd_refs:
        other_config = self._session.VBD.get_other_config(vbd_ref)
        if other_config.get('osvol'):
            (yield vbd_ref)
