[libvirt] libvirt support for hot plugging multifunction PCI devices to KVM guests

I'd like to understand where libvirt is with regards to supporting hot plugging of multifunction PCI devices to a KVM guest. http://www.redhat.com/archives/libvir-list/2011-December/msg00621.html According to the above thread,the --multifunction option can be specified with the virsh attach-disk command.What purpose does this option serve? Thanks, Nandini Chandra