VIRTIO_BLK(4)						   BSD Kernel Interfaces Manual 					     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 negoti-
	     ated.  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.

BSD
								   July 2, 2013 							       BSD