It is currently possible to use <interface>s of type openvswitch
with the libxl driver in a non-standard way, e.g.

  <interface type='bridge'>
    <source bridge='ovsbr0'/>
    <mac address='00:16:3e:7a:35:ce'/>
    <script path='vif-openvswitch'/>
  </interface>

This patch adds support for openvswitch <interface>s specified
in typical libvirt config

  <interface type='bridge'>
    <source bridge='ovsbr0'/>
    <mac address='00:16:3e:7a:35:ce'/>
    <virtualport type='openvswitch'/>
  </interface>

VLAN tags and trunking are also supported using the extended
syntax for specifying an openvswitch bridge in libxl

   BRIDGE_NAME[.VLAN][:TRUNK:TRUNK]

See Xen's networking wiki for more details on openvswitch support

https://wiki.xenproject.org/wiki/Xen_Networking#Open_vSwitchSigned-off-by: NJim Fehlig <jfehlig@suse.com>
ACKed-by: NMichal Privoznik <mprivozn@redhat.com>