Comment 85 for bug 378240

Here is a debdiff for the package.

As for the freeze exception, most of the rationale is already mentioned here. But to recap:

Xen packaging in Ubuntu is outdated and originates from a source outside of Debian. This patch will allow the usage of Debian xen package in Ubuntu. This package requires pulling xen-common package from Debian as well as rebuilding libvirt with libxen-dev as the dependency.

Current Xen packaging is horribly outdated and will hurt Ubuntu's image if a release is made with it.