def get_instance_vdis_for_sr(session, vm_ref, sr_ref):
    """Return opaqueRef for all the vdis which live on sr."""
    for vbd_ref in session.call_xenapi('VM.get_VBDs', vm_ref):
        try:
            vdi_ref = session.call_xenapi('VBD.get_VDI', vbd_ref)
            if sr_ref == session.call_xenapi('VDI.get_SR', vdi_ref):
                yield vdi_ref
        except session.XenAPI.Failure:
            continue
