1.\" Copyright (c) 2011 Bryan Venteicher 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.\" $FreeBSD: head/share/man/man4/virtio_blk.4 267938 2014-06-26 21:46:14Z bapt $ 26.\" 27.Dd December 10, 2014 28.Dt VIRTIO_BLK 4 29.Os 30.Sh NAME 31.Nm virtio_blk 32.Nd VirtIO Block driver 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following lines in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device virtio_blk" 39.Ed 40.Pp 41Alternatively, to load the driver as a 42module at boot time, place the following line in 43.Xr loader.conf 5 : 44.Bd -literal -offset indent 45virtio_blk_load="YES" 46.Ed 47.Sh DESCRIPTION 48The 49.Nm 50device driver provides support for VirtIO block devices. 51.Sh FILES 52.Bl -tag -width ".Pa /dev/vbdX" -compact 53.It Pa /dev/vbdX 54.Nm 55device nodes 56.El 57.Sh LOADER TUNABLES 58Tunables can be set at the 59.Xr loader 8 60prompt before booting the kernel or stored in 61.Xr loader.conf 5 . 62.Bl -tag -width "xxxxxx" 63.\".It Va hw.vtblk.no_ident 64.\".It Va hw.vtblk. Ns Ar X Ns Va .no_ident 65.\".Pp 66.\"These tunables disable retrieving the device identification string 67.\"from the hypervisor either globally or per-device. 68.\"The default value is 0. 69.It Va hw.vtblk.writecache_mode 70.It Va hw.vtblk. Ns Ar X Ns Va .writecache_mode 71.Pp 72These tunables determine the write cache mode globally or per-device. 73The mode can changed only if the ConfigWCE feature is negotiated. 74Set to 0 for writethrough mode, 1 for writeback mode, and -1 to leave 75it as-is. 76The default value is to leave as-is. 77.El 78.Sh SYSCTL VARIABLES 79The following variables are available as 80.Xr sysctl 8 81variables. 82.Bl -tag -width "xxxxxx" 83.It Va dev.vtblk. Ns Ar X Ns Va .writecache_mode 84.Pp 85The write cache mode of the device can be either writethrough (0) or 86writeback (1). 87If the ConfigWCE feature is negotiated, the write cache mode can 88be toggled between writethrough and writeback. 89.El 90.Sh SEE ALSO 91.Xr virtio 4 92.Sh HISTORY 93The 94.Nm 95driver was written by 96.An Bryan Venteicher Aq Mt bryanv@FreeBSD.org . 97It first appeared in 98.Fx 9.0 . 99