[libvirt] xen live migration with libvirt

The format of live migration command is "virsh migrate --live domain xen:/// xenmigr://remotehost" or another? My source and destination is rhel5.4 and xen is 3.1.0, libvirt is 0.8.2. I configured a shared storage between source and destination and modified /etc/xen/xend-config.sxp. I test the command "xm migrate --live domain remotehost" and it's going well. But when I use "virsh migrate --live domain xen:/// xenmigr://remotehost", a error appeared. error:post operation failed:xend_post:error from xen daemon:(xend.err '/usr/lib64/xen/bin/xc_save 23 2 0 0 5 failed') Regards, Best wishes.