143 lines
4.9 KiB
ReStructuredText
143 lines
4.9 KiB
ReStructuredText
.. BSD LICENSE
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Copyright(c) 2016 Intel Corporation. All rights reserved.
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of Intel Corporation nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.. _virtio_user_as_excpetional_path:
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Virtio_user as Exceptional Path
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===============================
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The virtual device, virtio-user, was originally introduced with vhost-user
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backend, as a high performance solution for IPC (Inter-Process Communication)
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and user space container networking.
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Virtio_user with vhost-kernel backend is a solution for exceptional path,
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such as KNI which exchanges packets with kernel networking stack. This
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solution is very promising in:
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* Maintenance
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All kernel modules needed by this solution, vhost and vhost-net (kernel),
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are upstreamed and extensively used kernel module.
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* Features
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vhost-net is born to be a networking solution, which has lots of networking
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related featuers, like multi queue, tso, multi-seg mbuf, etc.
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* Performance
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similar to KNI, this solution would use one or more kthreads to
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send/receive packets to/from user space DPDK applications, which has little
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impact on user space polling thread (except that it might enter into kernel
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space to wake up those kthreads if necessary).
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The overview of an application using virtio-user as exceptional path is shown
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in :numref:`figure_virtio_user_as_exceptional_path`.
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.. _figure_virtio_user_as_exceptional_path:
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.. figure:: img/virtio_user_as_exceptional_path.*
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Overview of a DPDK app using virtio-user as excpetional path
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Sample Usage
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------------
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As a prerequisite, the vhost/vhost-net kernel CONFIG should be chosen before
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compiling the kernel and those kernel modules should be inserted.
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#. Compile DPDK and bind a physical NIC to igb_uio/uio_pci_generic/vfio-pci.
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This physical NIC is for communicating with outside.
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#. Run testpmd.
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.. code-block:: console
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$(testpmd) -l 2-3 -n 4 \
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--vdev=virtio_user0,path=/dev/vhost-net,queue_size=1024 \
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-- -i --txqflags=0x0 --disable-hw-vlan --enable-lro \
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--enable-rx-cksum --rxd=1024 --txd=1024
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This command runs testpmd with two ports, one physical NIC to communicate
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with outside, and one virtio-user to communicate with kernel.
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* ``--enable-lro``
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This is used to negotiate VIRTIO_NET_F_GUEST_TSO4 and
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VIRTIO_NET_F_GUEST_TSO6 feature so that large packets from kernel can be
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transmitted to DPDK application and further TSOed by physical NIC.
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* ``--enable-rx-cksum``
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This is used to negotiate VIRTIO_NET_F_GUEST_CSUM so that packets from
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kernel can be deemed as valid Rx checksumed.
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* ``queue_size``
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256 by default. To avoid shortage of descriptors, we can increase it to 1024.
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* ``queues``
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Number of multi-queues. Each qeueue will be served by a kthread. For example:
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.. code-block:: console
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$(testpmd) -l 2-3 -n 4 \
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--vdev=virtio_user0,path=/dev/vhost-net,queues=2,queue_size=1024 \
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-- -i --txqflags=0x0 --disable-hw-vlan --enable-lro \
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--enable-rx-cksum --txq=2 --rxq=2 --rxd=1024 \
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--txd=1024
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#. Start testpmd:
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.. code-block:: console
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(testpmd) start
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#. Configure IP address and start tap:
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.. code-block:: console
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ifconfig tap0 1.1.1.1/24 up
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.. note::
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The tap device will be named tap0, tap1, etc, by kernel.
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Then, all traffic from physical NIC can be forwarded into kernel stack, and all
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traffic on the tap0 can be sent out from physical NIC.
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Limitations
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-----------
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This solution is only available on Linux systems.
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