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.. _vhost_user_input:
QEMU vhost-user-input - Input emulation
=======================================
This document describes the setup and usage of the Virtio input device.
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 \
...
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