add vnic type vdpa

This change extends the portbindings api extention
definition to add a new vnic typew "vdpa" to model
a vhost-vdpa simiar to the exisign vhost-user and
virtio-forwarder vnic types.

Change-Id: I01083fb8192b2ef00934af619576889b881c1249

neutron_lib/api/definitions/portbindings.py

@@ -117,9 +117,15 @@ VNIC_BAREMETAL = 'baremetal'
 VNIC_DIRECT_PHYSICAL = 'direct-physical'
 VNIC_VIRTIO_FORWARDER = 'virtio-forwarder'
 VNIC_SMARTNIC = 'smart-nic'
+# - vdpa:  The vHost-vdpa transport is a new vHost backend type introduced
+#          in qemu 5.1. vHost-vdpa leverages the vdpa framework introduced in
+#          kernel 5.7 to implement  a vhost offload of a standard virtio-net
+#          interface to a software or hardware backend.
+VNIC_VHOST_VDPA = 'vdpa'
 
 VNIC_TYPES = [VNIC_NORMAL, VNIC_DIRECT, VNIC_MACVTAP, VNIC_BAREMETAL,
-              VNIC_DIRECT_PHYSICAL, VNIC_VIRTIO_FORWARDER, VNIC_SMARTNIC]
+              VNIC_DIRECT_PHYSICAL, VNIC_VIRTIO_FORWARDER, VNIC_SMARTNIC,
+              VNIC_VHOST_VDPA]
 
 # VIF_DETAILS_CONNECTIVITY: Indicates what kind of connectivity the network
 #                           back-end provides: L2, L3 or not specified.

releasenotes/notes/vhost-vdpa-cc35f8d0ff9b3c4a.yaml

@@ -0,0 +1,14 @@
+---
+features:
+  - |
+    A new vnic type ``vdpa`` has been added to allow requesting port that
+    utilize a vhost-vdpa offload. vhost-vdpa is simpler to vhost-user or
+    kernel vhost offload but utilizes the newly added vdpa bus introduced
+    in the Linux 5.7 kernel. vdpa interface can be implemented in software
+    or hardware, when implemented in hardware they provide equivalent
+    performance to sr-iov or hardware offloaded ovs while have two main
+    advantages over both sriov and hardware offloaded ovs. Unlike the alternatives
+    vhost-vdpa enable live migration of instance transparently and provides
+    a standard virtio-net interface to the guest avoiding the need to install
+    vendor specific drivers  in the guest.
+