[libvirt] UID/GID during kvm/qemu migrate

Hello, is there some immanent code in libvirt that forces UID/GID of the libvirt standard user to be the same on two boxes migrating qemu vms against each other? The migration itself uses root obviously (password is requested). But if a vm xml does not contain any definition regarding UID/GID what else could prevent this from working? I believe I ran into such a problem trying to migrate and ending up in an error, a vm still working on original host but its fs (netfs pool (nfs/raw)) being switched to read-only... -- Regards, Stephan