Yes, libvirt is able to take advantage of libnuma calls into numad for
determining auto-placement of guest resources on a single node, rather
than spread out across multiple NUMA nodes, with the corresponding
performance improvements.  You can also request specific pinning rather
than relying on automatic placement.  For more details, here is the
portion of the XML that controls how libvirt will interact with numad:

http://libvirt.org/formatdomain.html#elementsNUMATuning