vm guest creation

If I am creating a kvm guest, I take it is doing something like

virt-install \ --name desktop1 \ --disk path=./moocow.qcow2 \ --ram 4098 --vcpus 2 \ --os-type linux \ [....] --arch x86_64

Where does it do that? And, how much control per guest do I have? I am looking at https://docs.openstack.org/mitaka/config-reference/compute/hypervisor-kvm.ht.... What I see is that I can only define across the border options in nova.conf. Also, are there any docs on configuring the libvirt besides https://wiki.openstack.org/wiki/LibvirtXMLConfigAPIs?