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qemu/docs/system/devices/virtio/vhost-user-contrib.rst

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vhost-user daemons in contrib
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
QEMU provides a number of :ref:`vhost_user` daemons in the contrib
directory. They were often written when vhost-user was initially added
to the code base. You should also consider if other vhost-user daemons
such as those from the rust-vmm `vhost-device repository`_ are better
suited for production use.
.. _vhost-device repository: https://github.com/rust-vmm/vhost-device
.. _vhost_user_block:
vhost-user-block - block device
===============================
vhost-user-block is a backend for exposing block devices. It can
present a flat file or block device as a simple block device to the
guest. You almost certainly want to use the :ref:`storage-daemon`
instead which supports a wide variety of storage modes and exports a
number of interfaces including vhost-user.
.. _vhost_user_gpu:
vhost-user-gpu - gpu device
===========================
vhost-user-gpu presents a paravirtualized GPU and display controller.
You probably want to use the internal :ref:`virtio_gpu` implementation
if you want the latest features. There is also a `vhost_device_gpu`_
daemon as part of the rust-vmm project.
.. _vhost_device_gpu: https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-gpu
.. _vhost_user_input:
vhost-user-input - Input emulation
==================================
The Virtio input device is a paravirtualized device for input events.
Description
-----------
The vhost-user-input device implementation was designed to work with a daemon
polling on input devices and passes input events to the guest.
QEMU provides a backend implementation in contrib/vhost-user-input.
Linux kernel support
--------------------
Virtio input requires a guest Linux kernel built with the
``CONFIG_VIRTIO_INPUT`` option.
Examples
--------
The backend daemon should be started first:
::
host# vhost-user-input --socket-path=input.sock \
--evdev-path=/dev/input/event17
The QEMU invocation needs to create a chardev socket to communicate with the
backend daemon and access the VirtIO queues with the guest over the
:ref:`shared memory <shared_memory_object>`.
::
host# qemu-system \
-chardev socket,path=/tmp/input.sock,id=mouse0 \
-device vhost-user-input-pci,chardev=mouse0 \
-m 4096 \
-object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
-numa node,memdev=mem \
...
.. _vhost_user_scsi:
vhost-user-scsi - SCSI controller
=================================
The vhost-user-scsi daemon can proxy iSCSI devices onto a virtualized
SCSI controller.