Added vif-vhostuser spec for juno
Change-Id: I03b432bb6d5554ece775c219aaa8c3d16195550f
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Luke Gorrie
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specs/juno/vif-vhostuser.rst
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specs/juno/vif-vhostuser.rst
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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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Create VIF_VHOSTUSER
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====================
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https://blueprints.launchpad.net/nova/+spec/vif-vhostuser
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We propose to add a new VIF type to support the new QEMU vhost-user
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feature. vhost-user is a new QEMU feature that supports efficient
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Virtio-net I/O between a guest and a user-space vswitch. vhost-user is
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the userspace equivalent to /dev/vhost-net and is based on a Unix
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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 NFV
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applications. (This is the reason that vhost-user was developed.)
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Proposed change
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===============
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This change defines nova.network.model.VIF_TYPE_VHOSTUSER.
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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 that want to assign certain ports to a userspace agent
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(vswitch) that is based on vhost-user.
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VIF_VHOSTUSER is to be implemented by extending the Libvirt driver.
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Libvirt support for vhost-user is currently under review and we expect
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it to be merged in time for Juno. We see that upstream Libvirt support
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for vhost-user is a dependency for merging the VIF_VHOSTUSER
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implementation into Nova.
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Alternatives
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------------
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Intel DPDK has a separate mechanism for accessing vhost from
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userspace, based on replacing /dev/vhost-net with a FUSE-based device
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file that traps ioctls into userspace. However, vhost-user is the new
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standard way to achieve this and is upstream in QEMU.
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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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vhost-user will make OpenStack compatible with vswitches supporting N
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x 10G Virtio-net workloads.
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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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Luke Gorrie <lukego>
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Other contributors:
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m.paolino
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Work Items
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----------
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* Add vhost-user support to the Libvirt driver.
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* Add VIF_VHOSTUSER support to Nova.
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Dependencies
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============
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* Libvirt must add support for vhost-user. Current patch under review:
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http://www.redhat.com/archives/libvir-list/2014-July/msg00111.html
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* VIF_VHOSTUSER will enable the Neutron driver for Snabb NFV:
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https://blueprints.launchpad.net/neutron/+spec/snabb-nfv-mech-driver
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http://snabb.co/nfv.html
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http://github.com/SnabbCo/snabbswitch
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Testing
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=======
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VIF_VHOSTUSER will be Tempest-tested by the planned 3rd party CI
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integration for the Snabb NFV 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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* Deutsche Telekom TeraStream project (initial user of VIF_VHOSTUSER):
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http://blog.ipspace.net/2013/11/deutsche-telekom-terastream-designed.html
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* Discussion from NFV BoF (Atlanta) etherpad:
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https://etherpad.openstack.org/p/juno-nfv-bof
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