Adding OVS Hardware Offload to TripleO

OVS Hardware Offload leverages SR-IOV technology to control the SR-IOV VF using VF representor port. OVS 2.8.0 supports the hw-offload option which allows to offload OVS datapath rule to hardware using linux traffic control tool and the VF representor port. This feature accelerates the OVS with a SR-IOV NIC which support switchdev mode.

Problem Description

Today the installation and configuration of OVS hardware offload feature is done manually after overcloud deployment. It shall be automated via tripleo.

Proposed Change


  • Configure the SR-IOV NIC to be in switchdev mode using the following syntax <physical_interface>:<numvfs>:<mode> for NeutronSriovNumVFs. mode can be legacy or switchdev

  • Configure the OVS with other_config:hw-offload. The options can be added for the cluster without side effects, because if then NIC doesn’t support OVS will fall-back to kernel datapath.

  • Nova scheduler should be configured to use the PciPassthroughFilter (same SR-IOV)

  • Nova compute should be configured with passthrough_whitelist (same SR-IOV)



Security Impact


Other End User Impact


Performance Impact

  • OVS Hardware Offload leverage the SR-IOV technology to provides near native I/O performance for each virtual machine that managed by OpenVswitch.

Other Deployer Impact

  • The operator shall ensure that the BIOS supports VT-d/IOMMU virtualization technology on the compute nodes.

  • IOMMU needs to be enabled in the Compute+SR-IOV nodes. Boot parameters (intel_iommu=on or amd_iommu=pt) shall be added in the grub.conf, using the PreNetworkConfig.

  • Post deployment, operator shall

    • Create neutron ports prior to creating VM’s (nova boot) openstack port create –vnic-type direct –binding-profile ‘{“capabilities”: [“switchdev”]}’ port1

    • Create the VM with the required flavor and SR-IOV port id openstack server create –image cirros-mellanox_sriov –port=port1 –flavor m1.tiny vm_a1

Developer Impact




Primary assignee:

waleedm (

Other contributors:

moshele (

Work Items

  • Update tripleo::host::sriov::numvfs_persistence to allow configure SR-IOV in switchdev mode. extending the vf_defs to <physical_interface>:<numvfs>:<mode>. Mode can be legacy which is default SR-IOV or switchdev which is used for ovs hardware offload.

  • Add a template parameter called NeutronOVSHwOffload to enable.

  • provide environment YAML for OVS hardware offload in tripleo-heat-templates.




  • Since SR-IOV needs specific hardware support, this feature can be tested under third party CI. We hope to provide Mellanox CI to SR-IOV and this feature.

Documentation Impact