Comment 5 for bug 1031063

$ virsh define /tmp/foo.xml
error: Failed to define domain from /tmp/foo.xml
error: internal error no supported architecture for os type 'hvm'

This means that libvirt can't find any way to provide the requested domain configuration. Since your XML shows you requested KVM, most likely this means that you have not got a KVM binary installed, or /dev/kvm does not exist.

Checking 'virsh capabilities' will show what ostype/hvtype/arch combinations libvirt has detected. Once you make virsh capabilities show the hvm+kvm+arch combination needed by the XML, then OpenStack should work as expected