freebsd-dev/share/man/man4/virtio.4

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.\" Copyright (c) 2011 Bryan Venteicher
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.Dd January 22, 2012
.Dt VIRTIO 4
.Os
.Sh NAME
.Nm virtio
.Nd VirtIO Device Support
.Sh SYNOPSIS
To compile VirtIO device support into the kernel, place the following lines
in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "device virtio"
.Cd "device virtio_pci"
.Ed
.Pp
Alternatively, to load VirtIO support as modules at boot time, place the
following lines in
.Xr loader.conf 5 :
.Bd -literal -offset indent
virtio_load="YES"
virtio_pci_load="YES"
.Ed
.Sh DESCRIPTION
VirtIO is a specification for para-virtualized I/O in a virtual machine (VM).
Traditionally, the hypervisor emulated real devices such as an Ethernet
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interface or disk controller to provide the VM with I/O.
This emulation is often inefficient.
.Pp
VirtIO defines an interface for efficient I/O between the hypervisor and VM.
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The
.Xr virtio 4
module provides a shared memory transport called a virtqueue.
The
.Xr virtio_pci 4
device driver represents an emulated PCI device that the hypervisor makes
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available to the VM.
This device provides the probing, configuration, and
interrupt notifications needed to interact with the hypervisor.
.Fx
supports the following VirtIO devices:
.Bl -hang -offset indent -width xxxxxxxx
.It Nm Ethernet
An emulated Ethernet device is provided by the
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.Xr vtnet 4
device driver.
.It Nm Block
An emulated disk controller is provided by the
.Xr virtio_blk 4
device driver.
.It Nm Balloon
A pseudo-device to allow the VM to release memory back to the hypervisor is
provided by the
.Xr virtio_balloon 4
device driver.
.El
.Sh SEE ALSO
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.Xr virtio_balloon 4 ,
.Xr virtio_blk 4 ,
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.Xr vtnet 4
.Sh HISTORY
Support for VirtIO first appeared in
.Fx 9.0 .
.Sh AUTHORS
.An -nosplit
.Fx
support for VirtIO was first added by
.An Bryan Venteicher Aq bryanv@daemoninthecloset.org .