[nova?] kvm/libvirt options

Which kvm options can I specify to an instance when I create it? I am looking at https://docs.openstack.org/nova/latest/admin/configuration/hypervisor-kvm.ht... and it has a handful of CPU ones (based on https://docs.openstack.org/nova/latest/configuration/config.html#libvirt), making me think the rest is some kind of openstack default which is a subset of what I can specify using, say, virsh define.