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doc: update vhost programming guide

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vhost-cuse has been removed in this release. Update the doc, with the
vhost-cuse part being removed.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>
This commit is contained in:
Yuanhan Liu 2016-11-02 11:14:59 +08:00 committed by Thomas Monjalon
parent 663c76798f
commit 647e191b54
1 changed files with 7 additions and 55 deletions
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62
doc/guides/prog_guide/vhost_lib.rst
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@ -46,26 +46,8 @@ vhost library should be able to:
* Know all the necessary information about the vring:
Information such as where the available ring is stored. Vhost defines some
messages to tell the backend all the information it needs to know how to
manipulate the vring.
Currently, there are two ways to pass these messages and as a result there are
two Vhost implementations in DPDK: *vhost-cuse* (where the character devices
are in user space) and *vhost-user*.
Vhost-cuse creates a user space character device and hook to a function ioctl,
so that all ioctl commands that are sent from the frontend (QEMU) will be
captured and handled.
Vhost-user creates a Unix domain socket file through which messages are
passed.
.. Note::
Since DPDK v2.2, the majority of the development effort has gone into
enhancing vhost-user, such as multiple queue, live migration, and
reconnect. Thus, it is strongly advised to use vhost-user instead of
vhost-cuse.
messages (passed through a Unix domain socket file) to tell the backend all
the information it needs to know how to manipulate the vring.
Vhost API Overview
@ -75,11 +57,10 @@ The following is an overview of the Vhost API functions:
* ``rte_vhost_driver_register(path, flags)``
This function registers a vhost driver into the system. For vhost-cuse, a
``/dev/path`` character device file will be created. For vhost-user server
mode, a Unix domain socket file ``path`` will be created.
This function registers a vhost driver into the system. ``path`` specifies
the Unix domain socket file path.
Currently supported flags are (these are valid for vhost-user only):
Currently supported flags are:
- ``RTE_VHOST_USER_CLIENT``
@ -171,35 +152,8 @@ The following is an overview of the Vhost API functions:
default.
Vhost Implementations
---------------------
Vhost-cuse 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 messages from the QEMU simulator.
When the open call is received, the vhost driver will create a vhost device
for the virtio device in the guest.
When the ``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
the guest virtual machine. Through this virtual address and the QEMU pid,
vhost can find the file QEMU uses to map the guest memory. Vhost maps this
file into its address space, in this way vhost can 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 the ``VHOST_NET_SET_BACKEND``
message. The registered callback from vSwitch will be called.
When the release call is made, vhost will destroy the device.
Vhost-user implementation
~~~~~~~~~~~~~~~~~~~~~~~~~
Vhost-user Implementations
--------------------------
Vhost-user uses Unix domain sockets for passing messages. This means the DPDK
vhost-user implementation has two options:
@ -246,8 +200,6 @@ For ``VHOST_SET_MEM_TABLE`` message, QEMU will send information for each
memory region and its file descriptor in the ancillary data of the message.
The file descriptor is used to map that region.
There is no ``VHOST_NET_SET_BACKEND`` message as in vhost-cuse to signal
whether the virtio device is ready or stopped. Instead,
``VHOST_SET_VRING_KICK`` is used as the signal to put the vhost device into
the data plane, and ``VHOST_GET_VRING_BASE`` is used as the signal to remove
the vhost device from the data plane.