There are few ways to easily migrate from XENSERVER to oVIRT, so I added that functionality into my backup tool.

You can access oVirt Simple Backup on git and enable the XEN options on it to migrate VMs directly from XEN into oVIRT. The VM has to shutdown for the migration, but it’s pretty simple to do.

oVirt Simple Backup is a plugin that install directly into the oVirt Engine WebUI.