4a22e6ee3d
This change adds automatic figure references to the docs. The figure numbers in the generated Html and PDF docs are now automatically numbered based on section. Requires Sphinx >= 1.3.1. The patch makes the following changes. * Changes image:: tag to figure:: and moves image caption to the figure. * Adds captions to figures that didn't previously have any. * Un-templates the |image-name| substitution definitions into explicit figure:: tags. They weren't used more than once anyway and Sphinx doesn't support them for figure. * Adds a target to each image that didn't previously have one so that they can be cross-referenced. * Renamed existing image target to match the image name for consistency. * Replaces the Figures lists with automatic :numref: :ref: entries to generate automatic numbering and captions. * Replaces "Figure" references with automatic :numref: references. Signed-off-by: John McNamara <john.mcnamara@intel.com>
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214 lines
9.0 KiB
ReStructuredText
.. BSD LICENSE
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Copyright(c) 2010-2014 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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Poll Mode Driver for Emulated Virtio NIC
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========================================
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Virtio is a para-virtualization framework initiated by IBM, and supported by KVM hypervisor.
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In the Data Plane Development Kit (DPDK),
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we provide a virtio Poll Mode Driver (PMD) as a software solution, comparing to SRIOV hardware solution,
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for fast guest VM to guest VM communication and guest VM to host communication.
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Vhost is a kernel acceleration module for virtio qemu backend.
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The DPDK extends kni to support vhost raw socket interface,
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which enables vhost to directly read/ write packets from/to a physical port.
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With this enhancement, virtio could achieve quite promising performance.
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In future release, we will also make enhancement to vhost backend,
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releasing peak performance of virtio PMD driver.
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For basic qemu-KVM installation and other Intel EM poll mode driver in guest VM,
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please refer to Chapter "Driver for VM Emulated Devices".
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In this chapter, we will demonstrate usage of virtio PMD driver with two backends,
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standard qemu vhost back end and vhost kni back end.
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Virtio Implementation in DPDK
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-----------------------------
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For details about the virtio spec, refer to Virtio PCI Card Specification written by Rusty Russell.
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As a PMD, virtio provides packet reception and transmission callbacks virtio_recv_pkts and virtio_xmit_pkts.
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In virtio_recv_pkts, index in range [vq->vq_used_cons_idx , vq->vq_ring.used->idx) in vring is available for virtio to burst out.
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In virtio_xmit_pkts, same index range in vring is available for virtio to clean.
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Virtio will enqueue to be transmitted packets into vring, advance the vq->vq_ring.avail->idx,
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and then notify the host back end if necessary.
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Features and Limitations of virtio PMD
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--------------------------------------
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In this release, the virtio PMD driver provides the basic functionality of packet reception and transmission.
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* It supports merge-able buffers per packet when receiving packets and scattered buffer per packet
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when transmitting packets. The packet size supported is from 64 to 1518.
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* It supports multicast packets and promiscuous mode.
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* The descriptor number for the RX/TX queue is hard-coded to be 256 by qemu.
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If given a different descriptor number by the upper application,
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the virtio PMD generates a warning and fall back to the hard-coded value.
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* Features of mac/vlan filter are supported, negotiation with vhost/backend are needed to support them.
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When backend can't support vlan filter, virtio app on guest should disable vlan filter to make sure
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the virtio port is configured correctly. E.g. specify '--disable-hw-vlan' in testpmd command line.
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* RTE_PKTMBUF_HEADROOM should be defined larger than sizeof(struct virtio_net_hdr), which is 10 bytes.
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* Virtio does not support runtime configuration.
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* Virtio supports Link State interrupt.
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* Virtio supports software vlan stripping and inserting.
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* Virtio supports using port IO to get PCI resource when uio/igb_uio module is not available.
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Prerequisites
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-------------
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The following prerequisites apply:
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* In the BIOS, turn VT-x and VT-d on
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* Linux kernel with KVM module; vhost module loaded and ioeventfd supported.
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Qemu standard backend without vhost support isn't tested, and probably isn't supported.
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Virtio with kni vhost Back End
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------------------------------
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This section demonstrates kni vhost back end example setup for Phy-VM Communication.
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.. _figure_host_vm_comms:
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.. figure:: img/host_vm_comms.*
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Host2VM Communication Example Using kni vhost Back End
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Host2VM communication example
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#. Load the kni kernel module:
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.. code-block:: console
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insmod rte_kni.ko
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Other basic DPDK preparations like hugepage enabling, uio port binding are not listed here.
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Please refer to the *DPDK Getting Started Guide* for detailed instructions.
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#. Launch the kni user application:
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.. code-block:: console
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examples/kni/build/app/kni -c 0xf -n 4 -- -p 0x1 -i 0x1 -o 0x2
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This command generates one network device vEth0 for physical port.
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If specify more physical ports, the generated network device will be vEth1, vEth2, and so on.
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For each physical port, kni creates two user threads.
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One thread loops to fetch packets from the physical NIC port into the kni receive queue.
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The other user thread loops to send packets in the kni transmit queue.
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For each physical port, kni also creates a kernel thread that retrieves packets from the kni receive queue,
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place them onto kni's raw socket's queue and wake up the vhost kernel thread to exchange packets with the virtio virt queue.
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For more details about kni, please refer to Chapter 24 "Kernel NIC Interface".
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#. Enable the kni raw socket functionality for the specified physical NIC port,
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get the generated file descriptor and set it in the qemu command line parameter.
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Always remember to set ioeventfd_on and vhost_on.
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Example:
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.. code-block:: console
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echo 1 > /sys/class/net/vEth0/sock_en
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fd=`cat /sys/class/net/vEth0/sock_fd`
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exec qemu-system-x86_64 -enable-kvm -cpu host \
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-m 2048 -smp 4 -name dpdk-test1-vm1 \
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-drive file=/data/DPDKVMS/dpdk-vm.img \
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-netdev tap, fd=$fd,id=mynet_kni, script=no,vhost=on \
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-device virtio-net-pci,netdev=mynet_kni,bus=pci.0,addr=0x3,ioeventfd=on \
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-vnc:1 -daemonize
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In the above example, virtio port 0 in the guest VM will be associated with vEth0, which in turns corresponds to a physical port,
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which means received packets come from vEth0, and transmitted packets is sent to vEth0.
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#. In the guest, bind the virtio device to the uio_pci_generic kernel module and start the forwarding application.
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When the virtio port in guest bursts rx, it is getting packets from the raw socket's receive queue.
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When the virtio port bursts tx, it is sending packet to the tx_q.
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.. code-block:: console
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modprobe uio
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echo 512 > /sys/devices/system/node/node0/hugepages/hugepages-2048kB/nr_hugepages
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modprobe uio_pci_generic
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python tools/dpdk_nic_bind.py -b uio_pci_generic 00:03.0
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We use testpmd as the forwarding application in this example.
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.. figure:: img/console.*
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Running testpmd
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#. Use IXIA packet generator to inject a packet stream into the KNI physical port.
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The packet reception and transmission flow path is:
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IXIA packet generator->82599 PF->KNI rx queue->KNI raw socket queue->Guest VM virtio port 0 rx burst->Guest VM virtio port 0 tx burst-> KNI tx queue->82599 PF-> IXIA packet generator
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Virtio with qemu virtio Back End
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--------------------------------
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.. _figure_host_vm_comms_qemu:
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.. figure:: img/host_vm_comms_qemu.*
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Host2VM Communication Example Using qemu vhost Back End
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.. code-block:: console
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qemu-system-x86_64 -enable-kvm -cpu host -m 2048 -smp 2 -mem-path /dev/
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hugepages -mem-prealloc
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-drive file=/data/DPDKVMS/dpdk-vm1
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-netdev tap,id=vm1_p1,ifname=tap0,script=no,vhost=on
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-device virtio-net-pci,netdev=vm1_p1,bus=pci.0,addr=0x3,ioeventfd=on
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-device pci-assign,host=04:10.1 \
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In this example, the packet reception flow path is:
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IXIA packet generator->82599 PF->Linux Bridge->TAP0's socket queue-> Guest VM virtio port 0 rx burst-> Guest VM 82599 VF port1 tx burst-> IXIA packet generator
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The packet transmission flow is:
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IXIA packet generator-> Guest VM 82599 VF port1 rx burst-> Guest VM virtio port 0 tx burst-> tap -> Linux Bridge->82599 PF-> IXIA packet generator
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