Comment 101 for bug 520386

Or you can try:

backportpackage -u ppa:<launchpaduser>/<launchpadrepo> -s quantal -d precise netcf
backportpackage -u ppa:<launchpaduser>/<launchpadrepo> -s quantal -d precise libvirt

However that will only work if there are no specific dependencies on other packages/versions that are only available in Quantal. At that point, you can either go down the dependency chain and backport them all (ugly), or fix the package to work with versions available in Precise (the previous post will start you in vaguely the right direction).