In a fairly unsurprising move Fedora 10 doesn’t include Xen Dom0 support in its most recent release. This is pretty quick considering little over a month ago Red Hat announced adopting KVM and acquiring the startup that maintains Qumranet.
Daniel P. Berrange laid it out. "There is pretty much zero chance that Fedora 10 will include a Xen Dom0 host. While upstream Xen developers are making good progress on porting Dom0 to paravirt_ops, there is simply too little time for this to be ready for Fedora 10. So if you need to use Fedora 10 as a host, then KVM is your only viable option at this time. If you can wait for Fedora 11 (or use RHEL-5 / CentOS-5) then Xen may be an option for you."