Description of problem: The version of virt-manager in FC6 does not support KVM. FC6 now has kernel 2.6.20 and the kvm module. All that is needed is (I guess) a newer virt-manager and the kvm package. Version-Release number of selected component (if applicable): virt-manager-0.2.6-3.fc6
Things are not that simple - it requires a KVM userspace, new libvirt, new virt-install and new virt-manager. While some of these bits may get updated in FC6 over time to resolve / improve Xen support, we've no plans to provide the KVM userspace at this time since it is a completely new package. Maintaining quality of the Xen support in FC6 takes priority over new features, particularly since Fedora 7 already has support for KVM and only has a 2 more test releases before GA.