This provides flexibility in multiprocess scenarios
(where the KNI is created in the primary process but the callbacks are handled in the secondary one).
The constraint is that a single process can register and handle the requests.
-
-KNI Working as a Kernel vHost Backend
--------------------------------------
-
-vHost is a kernel module usually working as the backend of virtio (a para- virtualization driver framework)
-to accelerate the traffic from the guest to the host.
-The DPDK Kernel NIC interface provides the ability to hookup vHost traffic into userspace DPDK application.
-Together with the DPDK PMD virtio, it significantly improves the throughput between guest and host.
-In the scenario where DPDK is running as fast path in the host, kni-vhost is an efficient path for the traffic.
-
-Overview
-~~~~~~~~
-
-vHost-net has three kinds of real backend implementations. They are: 1) tap, 2) macvtap and 3) RAW socket.
-The main idea behind kni-vhost is making the KNI work as a RAW socket, attaching it as the backend instance of vHost-net.
-It is using the existing interface with vHost-net, so it does not require any kernel hacking,
-and is fully-compatible with the kernel vhost module.
-As vHost is still taking responsibility for communicating with the front-end virtio,
-it naturally supports both legacy virtio -net and the DPDK PMD virtio.
-There is a little penalty that comes from the non-polling mode of vhost.
-However, it scales throughput well when using KNI in multi-thread mode.
-
-.. _figure_vhost_net_arch2:
-
-.. figure:: img/vhost_net_arch.*
-
- vHost-net Architecture Overview
-
-
-Packet Flow
-~~~~~~~~~~~
-
-There is only a minor difference from the original KNI traffic flows.
-On transmit side, vhost kthread calls the RAW socket's ops sendmsg and it puts the packets into the KNI transmit FIFO.
-On the receive side, the kni kthread gets packets from the KNI receive FIFO, puts them into the queue of the raw socket,
-and wakes up the task in vhost kthread to begin receiving.
-All the packet copying, irrespective of whether it is on the transmit or receive side,
-happens in the context of vhost kthread.
-Every vhost-net device is exposed to a front end virtio device in the guest.
-
-.. _figure_kni_traffic_flow:
-
-.. figure:: img/kni_traffic_flow.*
-
- KNI Traffic Flow
-
-
-Sample Usage
-~~~~~~~~~~~~
-
-Before starting to use KNI as the backend of vhost, the CONFIG_RTE_KNI_VHOST configuration option must be turned on.
-Otherwise, by default, KNI will not enable its backend support capability.
-
-Of course, as a prerequisite, the vhost/vhost-net kernel CONFIG should be chosen before compiling the kernel.
-
-#. Compile the DPDK and insert uio_pci_generic/igb_uio kernel modules as normal.
-
-#. Insert the KNI kernel module:
-
- .. code-block:: console
-
- insmod ./rte_kni.ko
-
- If using KNI in multi-thread mode, use the following command line:
-
- .. code-block:: console
-
- insmod ./rte_kni.ko kthread_mode=multiple
-
-#. Running the KNI sample application:
-
- .. code-block:: console
-
- examples/kni/build/app/kni -c -0xf0 -n 4 -- -p 0x3 -P --config="(0,4,6),(1,5,7)"
-
- This command runs the kni sample application with two physical ports.
- Each port pins two forwarding cores (ingress/egress) in user space.
-
-#. Assign a raw socket to vhost-net during qemu-kvm startup.
- The DPDK does not provide a script to do this since it is easy for the user to customize.
- The following shows the key steps to launch qemu-kvm with kni-vhost:
-
- .. code-block:: bash
-
- #!/bin/bash
- echo 1 > /sys/class/net/vEth0/sock_en
- fd=`cat /sys/class/net/vEth0/sock_fd`
- qemu-kvm \
- -name vm1 -cpu host -m 2048 -smp 1 -hda /opt/vm-fc16.img \
- -netdev tap,fd=$fd,id=hostnet1,vhost=on \
- -device virti-net-pci,netdev=hostnet1,id=net1,bus=pci.0,addr=0x4
-
-It is simple to enable raw socket using sysfs sock_en and get raw socket fd using sock_fd under the KNI device node.
-
-Then, using the qemu-kvm command with the -netdev option to assign such raw socket fd as vhost's backend.
-
-.. note::
-
- The key word tap must exist as qemu-kvm now only supports vhost with a tap backend, so here we cheat qemu-kvm by an existing fd.
-
-Compatibility Configure Option
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-There is a CONFIG_RTE_KNI_VHOST_VNET_HDR_EN configuration option in DPDK configuration file.
-By default, it set to n, which means do not turn on the virtio net header,
-which is used to support additional features (such as, csum offload, vlan offload, generic-segmentation and so on),
-since the kni-vhost does not yet support those features.
-
-Even if the option is turned on, kni-vhost will ignore the information that the header contains.
-When working with legacy virtio on the guest, it is better to turn off unsupported offload features using ethtool -K.
-Otherwise, there may be problems such as an incorrect L4 checksum error.
Code Review / deb_dpdk.git / blobdiff