xref: /freebsd/share/man/man4/virtio.4 (revision ddd5b8e9b4d8957fce018c520657cdfa4ecffad3)
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25.\" $FreeBSD$
26.\"
27.Dd January 22, 2012
28.Dt VIRTIO 4
29.Os
30.Sh NAME
31.Nm virtio
32.Nd VirtIO Device Support
33.Sh SYNOPSIS
34To compile VirtIO device support into the kernel, place the following lines
35in your kernel configuration file:
36.Bd -ragged -offset indent
37.Cd "device virtio"
38.Cd "device virtio_pci"
39.Ed
40.Pp
41Alternatively, to load VirtIO support as modules at boot time, place the
42following lines in
43.Xr loader.conf 5 :
44.Bd -literal -offset indent
45virtio_load="YES"
46virtio_pci_load="YES"
47.Ed
48.Sh DESCRIPTION
49VirtIO is a specification for para-virtualized I/O in a virtual machine (VM).
50Traditionally, the hypervisor emulated real devices such as an Ethernet
51interface or disk controller to provide the VM with I/O.
52This emulation is often inefficient.
53.Pp
54VirtIO defines an interface for efficient I/O between the hypervisor and VM.
55The
56.Xr virtio 4
57module provides a shared memory transport called a virtqueue.
58The
59.Xr virtio_pci 4
60device driver represents an emulated PCI device that the hypervisor makes
61available to the VM.
62This device provides the probing, configuration, and
63interrupt notifications needed to interact with the hypervisor.
64.Fx
65supports the following VirtIO devices:
66.Bl -hang -offset indent -width xxxxxxxx
67.It Nm Ethernet
68An emulated Ethernet device is provided by the
69.Xr vtnet 4
70device driver.
71.It Nm Block
72An emulated disk controller is provided by the
73.Xr virtio_blk 4
74device driver.
75.It Nm SCSI
76An emulated SCSI HBA is provided by the
77.Xr virtio_scsi 4
78device driver.
79.It Nm Balloon
80A pseudo-device to allow the VM to release memory back to the hypervisor is
81provided by the
82.Xr virtio_balloon 4
83device driver.
84.El
85.Sh SEE ALSO
86.Xr virtio_balloon 4 ,
87.Xr virtio_blk 4 ,
88.Xr virtio_scsi 4 ,
89.Xr vtnet 4
90.Sh HISTORY
91Support for VirtIO first appeared in
92.Fx 9.0 .
93.Sh AUTHORS
94.An -nosplit
95.Fx
96support for VirtIO was first added by
97.An Bryan Venteicher Aq bryanv@daemoninthecloset.org .
98