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93 lines
3.0 KiB
Groff
93 lines
3.0 KiB
Groff
.\" Copyright (c) 2011 Bryan Venteicher
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 2, 2013
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.Dt VIRTIO_BLK 4
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.Os
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.Sh NAME
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.Nm virtio_blk
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.Nd VirtIO Block driver
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following lines in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device virtio_blk"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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virtio_blk_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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device driver provides support for VirtIO block devices.
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.Sh LOADER TUNABLES
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Tunables can be set at the
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.Xr loader 8
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prompt before booting the kernel or stored in
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.Xr loader.conf 5 .
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.Bl -tag -width indent
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.It Va hw.vtblk.no_ident
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.It Va hw.vtblk. Ns Ar X Ns Va .no_ident
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.Pp
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These tunables disable retrieving the device identification string
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from the hypervisor either globally or per-device.
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The default value is 0.
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.It Va hw.vtblk.writecache_mode
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.It Va hw.vtblk. Ns Ar X Ns Va .writecache_mode
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.Pp
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These tunables determine the write cache mode globally or per-device.
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The mode can changed only if the ConfigWCE feature is negotiated.
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Set to 0 for writethrough mode, 1 for writeback mode, and -1 to leave
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it as-is.
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The default value is to leave as-is.
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.El
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.Sh SYSCTL VARIABLES
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The following variables are available as
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.Xr sysctl 8
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variables.
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.Bl -tag -width indent
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.It Va dev.vtblk. Ns Ar X Ns Va .writecache_mode
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.Pp
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The write cache mode of the device can be either writethrough (0) or
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writeback (1).
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If the ConfigWCE feature is negotiated, the write cache mode can
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be toggled between writethrough and writeback.
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.El
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.Sh SEE ALSO
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.Xr virtio 4
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.Sh HISTORY
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The
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.Nm
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driver was written by
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.An Bryan Venteicher Aq Mt bryanv@FreeBSD.org .
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It first appeared in
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.Fx 9.0 .
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