On 11/05/2014 10:50 AM, Thomas Stein wrote: I'm not exactly sure how well setvcpus --guest will work (or not) with windows guests. But the way it works for Linux guest is by telling the guest to treat an available cpu as offline; for this to work, the host must provide that cpu. So the error message makes sense. For --guest to have any chance of changing cpus from the guest perspective, you need something like <vcpu current='4'>4</vcpu> as your starting point, then tell the guest to offline 3 cpus shortly after boot, then later tell the guest to turn the cpus back on when you are ready to give it more power. The <address> element of a guest XML is related to what the _guest_ sees, not what the host provides. So it is perfectly fine for multiple guests to see the same <address> (each sees their own virtual hardware, and could care less if some other guest has similar virtual hardware). Similarly for the name of the <target> element - each guest will see their own guest-agent channel at the name 'org.qemu.guest_agent.0'; this is a guest view, so it doesn't matter whether other guests happen to also pick the same name. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org