Hi! > Clearly (b). For the default it is important that it is backward > compatible (to older libvirt versions) and works with as many guests as > possible. One very last counter-argument... Actually, even if we change our default, we are still backwards-compatible, because older libvirt automatically adds <address type='virtio-mmio'/> to the XML. So, all XMLs, created before the upgrade, will have it, so everything will keep working. The only thing affected by the change is domains created after the upgrade. You'll need to specify <address type='virtio-mmio'/> explicitly in order to work with older OSes. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list