The Xen team has recently merged a lot of Xen Dom0-related code into Linus' kernel tree. Two significant components that are still missing are the network and block backend drivers. Third-party kernels that have been patched to provide this functionality and may be found on the Fedora Xen mailing list. As the difference between the Linus and Xen trees descreases, it may make sense to patch the Fedora kernel to accelerate the adoption of these features. Otherwise, this bug may serve as a tracker as Linus accepts features into his tree.
See also https://fedoraproject.org/wiki/Features/XenPvopsDom0.
The network backend driver is in 2.6.39.
And blkback went in 3.0. The pciback went in 3.1
That feature is accepted for F16. I believe the drivers requested are already enabled there. I'm going to move this bug to F16 and close it as things should be set. If they aren't, please re-open.