Hello, (Not sure if this would be better suited for libvir-list, but here it goes!) I filed a bug last week regarding the way in which libvirt assigns addresses to virtio-serial ports. https://bugzilla.redhat.com/show_bug.cgi?id=1042505 To summarize, adding more than 31 ports causes problems because libvirt assigns them all to a single controller, which has a max of 31 (or less if the controller has a ports attribute). I was wondering, in general (eg. for things other than virtio-serial ports), are address assignments done by libvirt considered 'best efforts' (ie. we don't guarantee that it will work) or part of the 'promise' to the [API] user? (Ie. it should always result in a functioning virtual machine) I might be interested in working on a patch for this if it is considered worthwhile. Cheers, Jonathan