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.\" $FreeBSD$ 26.\" 27.Dd July 2, 2013 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 LOADER TUNABLES 52Tunables can be set at the 53.Xr loader 8 54prompt before booting the kernel or stored in 55.Xr loader.conf 5 . 56.Bl -tag -width indent 57.It Va hw.vtblk.no_ident 58.It Va hw.vtblk. Ns Ar X Ns Va .no_ident 59.Pp 60These tunables disable retrieving the device identification string 61from the hypervisor either globally or per-device. 62The default value is 0. 63.It Va hw.vtblk.writecache_mode 64.It Va hw.vtblk. Ns Ar X Ns Va .writecache_mode 65.Pp 66These tunables determine the write cache mode globally or per-device. 67The mode can changed only if the ConfigWCE feature is negotiated. 68Set to 0 for writethrough mode, 1 for writeback mode, and -1 to leave 69it as-is. 70The default value is to leave as-is. 71.El 72.Sh SYSCTL VARIABLES 73The following variables are available as 74.Xr sysctl 8 75variables. 76.Bl -tag -width indent 77.It Va dev.vtblk. Ns Ar X Ns Va .writecache_mode 78.Pp 79The write cache mode of the device can be either writethrough (0) or 80writeback (1). 81If the ConfigWCE feature is negotiated, the write cache mode can 82be toggled between writethrough and writeback. 83.El 84.Sh SEE ALSO 85.Xr virtio 4 86.Sh HISTORY 87The 88.Nm 89driver was written by 90.An Bryan Venteicher Aq Mt bryanv@FreeBSD.org . 91It first appeared in 92.Fx 9.0 . 93