547a3fa4fa
Just move implemented specs to the right place. Change-Id: Ia09ed6aceb9e9874e07c740d2fe94ce1b88af9f7
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178 lines
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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============================================
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Add VIF_VHOSTUSER vif type to libvirt driver
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============================================
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https://blueprints.launchpad.net/nova/+spec/libvirt-vif-vhost-user
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We propose to add a new VIF type to support the new QEMU vhost-user
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interface in libvirt dirver. vhost-user is a new QEMU feature that supports
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efficient Virtio-net I/O between a guest and a user-space vswitch.
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vhost-user is the userspace equivalent to /dev/vhost-net and is based on
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a Unix socket for communication instead of a kernel device file.
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Problem description
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===================
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QEMU has a new type of network interface, vhost-user, and we want to
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make this available to Neutron drivers. This will support deploying
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high-throughput userspace vswitches for OpenStack-based applications.
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There are two types of vSwitches that can use vhost-user
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interface, a generic vhost-user vSwitch and ovs based one, both types
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should be supported.
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Use Cases
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---------
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This change will allow running userspace vSwitches using vhost-user
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interface. Both generic vhost-user vSwitches and OVS based vSwtiches
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will be supported.
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Project Priority
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----------------
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No
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Proposed change
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===============
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We propose to add VIF_VHOSTUSER to Nova for creating network
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interfaces based on vhost-user. This VIF type would be enabled by
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Neutron drivers by using portbindings extension and setting the
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vif_type to VIF_VHOSTUSER. To support both generic and ovs based
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vSwitches additional information will be passed in vif_details.
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For ovs based vSwitches plug/unplug methods will create/remove
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an ovs port if 'vhost_user_ovs_plug' is set to True in the vif_details.
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VIF_VHOSTUSER driver will allow Neutron mechanism drivers to specify
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if qemu should work in server or client mode. Mechanism drivers
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could pass 'vhost_user_mode' in vif_details to specify the mode.
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The name of the socket will be the same as ID of the Neutron port.
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For ovs based vSwitches name of the socket will be the same as name
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of the ovs port.
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Alternatives
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------------
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In Juno cycle there were two initiatives to support userspace vhost user
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in Nova. One was based on vhost-user interface in Qemu the other was based
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on DPDK implementation. Since DPDK is moving to support vhost-user only one
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driver is needed.
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Alternatively a mechanism for plugging in vif libvirt driver could be used
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to support
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vhost-user in libvirt driver. Such mechanism is proposed here:
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https://blueprints.launchpad.net/nova/+spec/libvirt-vif-driver-plugin
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Data model impact
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-----------------
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None.
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REST API impact
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---------------
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None.
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Security impact
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---------------
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None.
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Notifications impact
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--------------------
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None.
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Other end user impact
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---------------------
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None.
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Performance Impact
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------------------
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Use of VIF_VHOSTUSER will have no inpact on Openstack performance.
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Use of userspace vSwitch with vhost-user will improve guest network perforamce.
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Other deployer impact
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---------------------
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VIF_VHOSTUSER does not have to be enabled by the deployer. Neutron
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drivers will automatically enable VIF_VHOSTUSER via port binding if
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this is the appropriate choice for the agent on the compute host.
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VIF_VHOSTUSER will require a version of QEMU with vhost-user support,
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which is currently upstream and will be released in QEMU 2.1.
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VIF_VHOSTUSER will also require a version of Libvirt with vhost-user
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support.
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Developer impact
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----------------
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None.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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Przemyslaw Czesnowicz <pczesno>
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Work Items
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----------
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* Add VIF_VHOSTUSER support to Nova.
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Dependencies
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============
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An ml2 dpdk ovs driver is being proposed for Neutron.
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This feature doesn't directly depend on it.
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This feature depends on bp/virt-driver-large-pages.
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Testing
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=======
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VIF_VHOSTUSER will be tested by 3rd party CI for the DPDK Ovs mech driver.
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Documentation Impact
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====================
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No documentation changes for Nova are anticipated. VIF_VHOSTUSER will
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be automatically enabled by Neutron where appropriate.
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References
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==========
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* vhost-user:
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http://www.virtualopensystems.com/en/solutions/guides/snabbswitch-qemu/
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* Snabb NFV (initial vswitch supporting vhost-user): http://snabb.co/nfv.html
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* Juno spec for VIF_VHOSTUSER:
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https://review.openstack.org/#/c/96138/
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* Juno spec for dpdkvhost
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https://review.openstack.org/#/c/95805/4/specs/juno/libvirt-ovs-use-usvhost.rst
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* Neutron dpdk-ovs mechanism driver
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https://blueprints.launchpad.net/neutron/+spec/ml2-dpdk-ovs-mechanism-driver
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* Blueprint for vif plugin mechanism.
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https://blueprints.launchpad.net/nova/+spec/libvirt-vif-driver-plugin
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* Blueprint for Hugepage support
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https://blueprints.launchpad.net/nova/+spec/virt-driver-large-pages
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