In our lab setup we setup contrail and openstack in an ESXi and Virtualbox environments.
The installation went through fine, however when trying to spawn a new instance from Openstack, we were receiving the following error "Can't create instance, no valid host was found".
The compute logs logs under /var/log/nova# more nova-compute.log showed:
"Error: internal error: no supported architecture for os type 'hvm'"
We had to edit the following file: /etc/nova/nova-compute.conf and change the virt_type from kvm to qemu.
root@Openstack-Contrail:/etc/nova# cat nova-compute.conf[DEFAULT]compute_driver=libvirt.LibvirtDriver[libvirt]virt_type=qemu
Thereafter we had to restart the nova-compute service: # service nova-compute restart
After which we were able to successfully spawn the new instance.