.\" .\" Copyright (c) 2016 Alexander Motin .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" .Dd July 28, 2016 .Dt NTB_HW 4 .Os .Sh NAME .Nm ntb , .Nm ntb_hw .Nd Intel(R) Non-Transparent Bridge driver .Sh SYNOPSIS To compile this driver into your kernel, place the following lines in your kernel configuration file: .Bd -ragged -offset indent .Cd "device ntb_hw" .Ed .Pp Or, to load the driver as a module at boot, place the following line in .Xr loader.conf 5 : .Bd -literal -offset indent ntb_hw_load="YES" .Ed .Pp The following tunables are settable from the .Xr loader 8 : .Bl -ohang .It Va hw.ntb.debug_level Driver debug level. The default value is 0, higher means more verbose. .It Va hint.ntb_hw. Ns Ar X Ns Va .config Configures NTB resources split between several consumer devices. Configuration of multiple consumer devices separated by commas. Each device can be configured as: "[:[:[:]]]", where: .Va name is a name of the driver which should attach the device (empty means any), .Va mw is a number of memory windows to allocate (empty means all available), .Va spad is a number of scratchpad registers to allocate (empty means all available), .Va db is a number of doorbells to allocate (empty means all available). The default configuration is empty string, which means single device with all available resources allowing any driver attachment. .El .Sh DESCRIPTION The NTB allows you to connect two computer systems using a PCIe link if they have the correct equipment and connectors. The .Nm ntb_hw driver provides support for the Non-Transparent Bridge (NTB) in the Intel S1200 and Xeon E3/E5 processor families. The .Nm driver hides hardware details, exposing memory windows, scratchpads and doorbells via hardware independent KPI. .Pp The hardware provides 2-3 memory windows to the other system's memory, 16 scratchpad registers and 14/34 doorbells to interrupt the other system. On Xeon processors one of memory windows is typically consumed by the driver to workaround multiple hardware erratas. .Sh CONFIGURATION The NTB configuration should be set by BIOS. It includes enabling NTB, choosing between NTB-to-NTB or NTB-to-Root Port mode, enabling split BAR mode (one of two 64-bit BARs can be split into two 32-bit ones) and configuring BAR sizes in bits (from 12 to 29/39) for both NTB sides. .Pp The recommended configuration is NTB-to-NTB mode, split bar is enabled and all BAR sizes are set to 20 (1 MiB). This needs to be done on both systems. .Sh SEE ALSO .Xr ntb_transport 4 , .Xr if_ntb 4 .Sh AUTHORS .An -nosplit The .Nm driver was developed by Intel and originally written by .An Carl Delsey Aq Mt carl@FreeBSD.org . Later improvements were done by .An Conrad E. Meyer Aq Mt cem@FreeBSD.org and .An Alexander Motin Aq Mt mav@FreeBSD.org . .Sh BUGS NTB-to-Root Port mode is not yet supported, but it doesn't look very useful. .Pp On Xeon v2/v3/v4 processors split BAR mode should be enabled to allow SB01BASE_LOCKUP errata workaround to be applied by the driver. .Pp There is no way to protect your system from malicious behavior on the other system once the link is brought up. Anyone with root or kernel access on the other system can read or write to any location on your system. In other words, only connect two systems that completely trust each other.