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diff --git a/doc/guides/howto/virtio_user_as_exceptional_path.rst b/doc/guides/howto/virtio_user_as_exceptional_path.rst new file mode 100644 index 00000000..0bbcd3fd --- /dev/null +++ b/doc/guides/howto/virtio_user_as_exceptional_path.rst @@ -0,0 +1,142 @@ +.. BSD LICENSE + Copyright(c) 2016 Intel Corporation. All rights reserved. + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + * Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in + the documentation and/or other materials provided with the + distribution. + * Neither the name of Intel Corporation nor the names of its + contributors may be used to endorse or promote products derived + from this software without specific prior written permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +.. _virtio_user_as_excpetional_path: + +Virtio_user as Exceptional Path +=============================== + +The virtual device, virtio-user, was originally introduced with vhost-user +backend, as a high performance solution for IPC (Inter-Process Communication) +and user space container networking. + +Virtio_user with vhost-kernel backend is a solution for exceptional path, +such as KNI which exchanges packets with kernel networking stack. This +solution is very promising in: + +* Maintenance + + All kernel modules needed by this solution, vhost and vhost-net (kernel), + are upstreamed and extensively used kernel module. + +* Features + + vhost-net is born to be a networking solution, which has lots of networking + related featuers, like multi queue, tso, multi-seg mbuf, etc. + +* Performance + + similar to KNI, this solution would use one or more kthreads to + send/receive packets from user space DPDK applications, which has little + impact on user space polling thread (except that it might enter into kernel + space to wake up those kthreads if necessary). + +The overview of an application using virtio-user as exceptional path is shown +in :numref:`figure_virtio_user_as_exceptional_path`. + +.. _figure_virtio_user_as_exceptional_path: + +.. figure:: img/virtio_user_as_exceptional_path.* + + Overview of a DPDK app using virtio-user as excpetional path + + +Sample Usage +------------ + +As a prerequisite, the vhost/vhost-net kernel CONFIG should be chosen before +compiling the kernel and those kernel modules should be inserted. + +#. Compile DPDK and bind a physical NIC to igb_uio/uio_pci_generic/vfio-pci. + + This physical NIC is for communicating with outside. + +#. Run testpmd. + + .. code-block:: console + + $(testpmd) -l 2-3 -n 4 \ + --vdev=virtio_user0,path=/dev/vhost-net,queue_size=1024 \ + -- -i --txqflags=0x0 --disable-hw-vlan --enable-lro \ + --enable-rx-cksum --rxd=1024 --txd=1024 + + This command runs testpmd with two ports, one physical NIC to communicate + with outside, and one virtio-user to communicate with kernel. + +* ``--enable-lro`` + + This is used to negotiate VIRTIO_NET_F_GUEST_TSO4 and + VIRTIO_NET_F_GUEST_TSO6 feature so that large packets from kernel can be + transmitted DPDK application and further TSOed by physical NIC. + +* ``--enable-rx-cksum`` + + This is used to negotiate VIRTIO_NET_F_GUEST_CSUM so that packets from + kernel can be deemed as valid Rx checksumed. + +* ``queue_size`` + + 256 by default. To avoid shortage of descriptors, we can increase it to 1024. + +* ``queues`` + + Number of multi-queues. Each qeueue will be served by a kthread. For example: + + .. code-block:: console + + $(testpmd) -l 2-3 -n 4 \ + --vdev=virtio_user0,path=/dev/vhost-net,queues=2,queue_size=1024 \ + -- -i --txqflags=0x0 --disable-hw-vlan --enable-lro \ + --enable-rx-cksum --txq=2 --rxq=2 --rxd=1024 \ + --txd=1024 + +#. Start testpmd: + + .. code-block:: console + + (testpmd) start + +#. Configure IP address and start tap: + + .. code-block:: console + + ifconfig tap0 1.1.1.1/24 up + +.. note:: + + The tap device will be named tap0, tap1, etc, by kernel. + +Then, all traffic from physical NIC can be forwarded into kernel stack, and all +traffic on the tap0 can be sent out from physical NIC. + +Limitations +----------- + +This solution is only available on Linux systems. |