Guests created in OpenXT 8 and before will no longer be able to boot after upgrading to OpenXT 9.
Upgrade rules to support the transition from V4V to Argo are not ran by the 9.0.0 and 9.0.1 version.
OpenXT 9, Dom0.
install OpenXT 8
create an HVM guest with stubdomain
upgrade to latest OpenXT 9
Once rebooted in the upgraded OpenXT 9, the guest should start without error.