---
upgrade:
  - |
    The ``[xenserver]/vif_driver`` configuration option was deprecated in
    the 15.0.0 Ocata release and has now been removed. The only supported
    vif driver is now ``XenAPIOpenVswitchDriver`` used with Neutron as the
    backend networking service configured to run the
    ``neutron-openvswitch-agent`` service. See the `XenServer configuration
    guide`_ for more details on networking setup.

    .. _XenServer configuration guide: https://docs.openstack.org/nova/latest/admin/configuration/hypervisor-xen-api.html