Use the following command to migrate the guest.
host1# virsh migrate domain --live xen:// xenmigr://target-host
While the use of the virsh command is preferred, you can try the following command if the virsh command appears to fail.
host1# xm migrate -l domain target-host
You can observe the migration while it occurs by monitoring the domain status on both machines using virsh list.
Note that the domain definition remains on the system on which it was created. You can start the domain on that system's dom0 with the virsh start domain command.