VIRTIO_BLK(4)

NAME
virtio_blk - VirtIO Block driver

SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file:

device virtio_blk

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

    virtio_blk_load="YES"

DESCRIPTION
The virtio_blk device driver provides support for VirtIO block devices.

LOADER TUNABLES
Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).

hw.vtblk.no_ident

hw.vtblk.X.no_ident

    These tunables disable retrieving the device identification string from the hypervisor either globally or per-device. The default value is 0.

hw.vtblk.writecache_mode

hw.vtblk.X.writecache_mode

    These tunables determine the write cache mode globally or per-device. The mode can changed only if the ConfigWCE feature is negotiated. Set to 0 for writethrough mode, 1 for writeback mode, and -1 to leave it as-is. The default value is to leave as-is.

SYSCTL VARIABLES
The following variables are available as sysctl(8) variables.

dev.vtblk.X.writecache_mode

    The write cache mode of the device can be either writethrough (0) or writeback (1). If the ConfigWCE feature is negotiated, the write cache mode can be toggled between writethrough and writeback.

SEE ALSO
virtio(4)

HISTORY
The virtio_blk driver was written by Bryan Venteicher <bryanv@FreeBSD.org>. It first appeared in FreeBSD 9.0.