1.\" 2.\" Copyright (c) 2016-2017 Alexander Motin <mav@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd August 30, 2017 29.Dt NTB_HW_INTEL 4 30.Os 31.Sh NAME 32.Nm ntb_hw_intel 33.Nd Intel(R) Non-Transparent Bridge driver 34.Sh SYNOPSIS 35To compile this driver into your kernel, 36place the following lines in your kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "device ntb" 39.Cd "device ntb_hw_intel" 40.Ed 41.Pp 42Or, to load the driver as a module at boot, place the following line in 43.Xr loader.conf 5 : 44.Bd -literal -offset indent 45ntb_hw_intel_load="YES" 46.Ed 47.Sh DESCRIPTION 48The 49.Nm ntb_hw_intel 50driver provides support for the Non-Transparent Bridge (NTB) hardware in 51Intel Xeon E3/E5 and S1200 processor families, which allow one of their PCIe 52ports to be switched from transparent to non-transparent bridge mode. 53In this mode bridge looks not as a PCI bridge, but as PCI endpoint device. 54The driver hides hardware details, exposing memory windows, scratchpads 55and doorbells of the other side via hardware independent KPI to 56.Xr ntb 4 57subsystem. 58.Pp 59The hardware provides 2 or 3 memory windows to the other system's memory, 6016 scratchpad registers and 14 or 34 doorbells to interrupt the other system. 61On Xeon processors one of memory windows is typically consumed by the driver 62itself to workaround multiple hardware erratas. 63.Sh CONFIGURATION 64The NTB configuration should be set by BIOS. 65It includes enabling NTB, choosing between NTB-to-NTB (back-to-back) or 66NTB-to-Root Port mode, 67enabling split BAR mode (one of two 64-bit BARs can be split into two 32-bit 68ones) and configuring BAR sizes in bits (from 12 to 29/39) for both NTB sides. 69.Pp 70The recommended configuration is NTB-to-NTB mode, split bar is enabled and 71all BAR sizes are set to 20 (1 MiB). 72This needs to be done on both systems. 73.Sh SEE ALSO 74.Xr if_ntb 4 , 75.Xr ntb_transport 4 , 76.Xr ntb 4 , 77.Sh AUTHORS 78.An -nosplit 79The 80.Nm 81driver was developed by Intel and originally written by 82.An Carl Delsey Aq Mt carl@FreeBSD.org . 83Later improvements were done by 84.An Conrad E. Meyer Aq Mt cem@FreeBSD.org 85and 86.An Alexander Motin Aq Mt mav@FreeBSD.org . 87.Sh BUGS 88NTB-to-Root Port mode is not yet supported, but it doesn't look very useful. 89.Pp 90On Xeon v2/v3/v4 processors split BAR mode should be enabled to allow 91SB01BASE_LOCKUP errata workaround to be applied by the driver. 92.Pp 93There is no way to protect your system from malicious behavior on the other 94system once the link is brought up. 95Anyone with root or kernel access on the other system can read or write to 96any location on your system. 97In other words, only connect two systems that completely trust each other. 98