Hi
I was able to boot Fedora 15 as Dom0 under xen 4.1.1
with backported and fixed version of /etc/grub.d/20_linux_xen from Fedora 16's grub2.
I use stock Fedora 15 kernel 2.6.40-4.fc15.x86_64.
It has all Xen drivers compiled and it is able to boot as Dom0.
Regards,
Marko Ristola