From 0ee5e7fb93aefe9bccb6a9c331cfe27c14bc7ec6 Mon Sep 17 00:00:00 2001 From: Siobhan Butler Date: Tue, 2 Dec 2014 21:11:42 +0000 Subject: [PATCH] doc: add vhost library As Vhost will be a library in DPDK 1.8, adding a new section to Programmer's Guide to describe its use. Signed-off-by: Siobhan Butler Signed-off-by: Huawei Xie Acked-by: Bernard Iremonger --- doc/guides/prog_guide/index.rst | 1 + doc/guides/prog_guide/vhost_lib.rst | 101 ++++++++++++++++++++++++++++ 2 files changed, 102 insertions(+) create mode 100644 doc/guides/prog_guide/vhost_lib.rst diff --git a/doc/guides/prog_guide/index.rst b/doc/guides/prog_guide/index.rst index e0ac8f4dc7..6652cb4747 100644 --- a/doc/guides/prog_guide/index.rst +++ b/doc/guides/prog_guide/index.rst @@ -106,6 +106,7 @@ Copyright © 2012-2014, Intel Corporation. All rights reserved. power_man packet_classif_access_ctrl packet_framework + vhost_lib source_org dev_kit_build_system dev_kit_root_make_help diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst new file mode 100644 index 0000000000..0b6eda7836 --- /dev/null +++ b/doc/guides/prog_guide/vhost_lib.rst @@ -0,0 +1,101 @@ +.. BSD LICENSE + Copyright(c) 2010-2014 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. + +Vhost Library +============= + +The vhost cuse (cuse: user space character device driver) library implements a +vhost cuse driver. It also creates, manages and destroys vhost devices for +corresponding virtio devices in the guest. Vhost supported vSwitch could register +callbacks to this library, which will be called when a vhost device is activated +or deactivated by guest virtual machine. + +Vhost API Overview +------------------ + +* Vhost driver registration + + rte_vhost_driver_register registers the vhost cuse driver into the system. + Character device file will be created in the /dev directory. + Character device name is specified as the parameter. + +* Vhost session start + + rte_vhost_driver_session_start starts the vhost session loop. + Vhost cuse session is an infinite blocking loop. + Put the session in a dedicate DPDK thread. + +* Callback register + + Vhost supported vSwitch could call rte_vhost_driver_callback_register to + register two callbacks, new_destory and destroy_device. + When virtio device is activated or deactivated by guest virtual machine, + the callback will be called, then vSwitch could put the device onto data + core or remove the device from data core. + +* Read/write packets from/to guest virtual machine + + rte_vhost_enqueue_burst transmit host packets to guest. + rte_vhost_dequeue_burst receives packets from guest. + +* Feature enable/disable + + Now one negotiate-able feature in vhost is merge-able. + vSwitch could enable/disable this feature for performance consideration. + +Vhost Implementation +-------------------- + +When vSwitch registers the vhost driver, it will register a cuse device driver +into the system and creates a character device file. This cuse driver will +receive vhost open/release/IOCTL message from QEMU simulator. + +When the open call is received, vhost driver will create a vhost device for the +virtio device in the guest. + +When VHOST_SET_MEM_TABLE IOCTL is received, vhost searches the memory region +to find the starting user space virtual address that maps the memory of guest +virtual machine. Through this virtual address and the QEMU pid, vhost could +find the file QEMU uses to map the guest memory. Vhost maps this file into its +address space, in this way vhost could fully access the guest physical memory, +which means vhost could access the shared virtio ring and the guest physical +address specified in the entry of the ring. + +The guest virtual machine tells the vhost whether the virtio device is ready +for processing or is de-activated through VHOST_SET_BACKEND message. +The registered callback from vSwitch will be called. + +When the release call is released, vhost will destroy the device. + +Vhost supported vSwitch reference +--------------------------------- + +For how to support vhost in vSwitch, please refer to vhost example in the +DPDK Sample Applications Guide. -- 2.20.1