Use fence_kvm, do googling for details.
This how to create stonith in pcs
[root@nfs01 ~]# pcs stonith create xvm-fence-nfs01 fence_xvm port="nfs01" pcmk_host_list="nfs01"
[root@nfs01 ~]# pcs stonith create xvm-fence-nfs02 fence_xvm port="nfs02" pcmk_host_list="nfs02"