Comment 6 for bug 368962

I really don't consider this High importance at all[1], and I doubt this will get fixed any time soon, if ever. There's simply no portable way (that I can think of, at least) to reboot a fully virtualised operating system, and until there is, such a method cannot be exposed through the libvirt API. Think of it this way: There's no way to walk up to a physical machine and reboot the operating system on there without knowing which operating system it's running and subsequently knowing specifically how to reboot said operating system (if said operating system even /has/ a mechanism for that). That's basically what you're asking libvirt/kvm to be able to do.

[1]: https://wiki.ubuntu.com/Bugs/Importance