1.\" 2.\" Copyright (c) 2012-2013 Intel Corporation 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.\" without modification. 11.\" 2. Redistributions in binary form must reproduce at minimum a disclaimer 12.\" substantially similar to the "NO WARRANTY" disclaimer below 13.\" ("Disclaimer") and any redistribution must be conditioned upon 14.\" including a substantially similar Disclaimer requirement for further 15.\" binary redistribution. 16.\" 17.\" NO WARRANTY 18.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR 21.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22.\" HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 26.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 27.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28.\" POSSIBILITY OF SUCH DAMAGES. 29.\" 30.\" nvme driver man page. 31.\" 32.\" Author: Jim Harris <jimharris@FreeBSD.org> 33.\" 34.\" $FreeBSD$ 35.\" 36.Dd July 9, 2013 37.Dt NVME 4 38.Os 39.Sh NAME 40.Nm nvme 41.Nd NVM Express core driver 42.Sh SYNOPSIS 43To compile this driver into your kernel, 44place the following line in your kernel configuration file: 45.Bd -ragged -offset indent 46.Cd "device nvme" 47.Ed 48.Pp 49Or, to load the driver as a module at boot, place the following line in 50.Xr loader.conf 5 : 51.Bd -literal -offset indent 52nvme_load="YES" 53.Ed 54.Pp 55Most users will also want to enable 56.Xr nvd 4 57to surface NVM Express namespaces as disk devices. 58Note that in NVM Express terms, a namespace is roughly equivalent to a 59SCSI LUN. 60.Sh DESCRIPTION 61The 62.Nm 63driver provides support for NVM Express (NVMe) controllers, such as: 64.Bl -bullet 65.It 66Hardware initialization 67.It 68Per-CPU IO queue pairs 69.It 70API for registering NVMe namespace consumers such as 71.Xr nvd 4 72.It 73API for submitting NVM commands to namespaces 74.It 75Ioctls for controller and namespace configuration and management 76.Pp 77.Nm 78creates controller devices in the format 79.Pa /dev/nvmeX 80and namespace devices in 81the format 82.Pa /dev/nvmeXnsY . 83Note that the NVM Express specification starts numbering namespaces at 1, 84not 0, and this driver follows that convention. 85.El 86.Sh CONFIGURATION 87By default, 88.Nm 89will create an I/O queue pair for each CPU, provided enough MSI-X vectors 90can be allocated. 91To force a single I/O queue pair shared by all CPUs, set the following 92tunable value in 93.Xr loader.conf 5 : 94.Bd -literal -offset indent 95hw.nvme.per_cpu_io_queues=0 96.Ed 97.Pp 98To force legacy interrupts for all 99.Nm 100driver instances, set the following tunable value in 101.Xr loader.conf 5 : 102.Bd -literal -offset indent 103hw.nvme.force_intx=1 104.Ed 105.Pp 106Note that use of INTx implies disabling of per-CPU I/O queue pairs. 107.Sh SYSCTL VARIABLES 108The following controller-level sysctls are currently implemented: 109.Bl -tag -width indent 110.It Va dev.nvme.0.int_coal_time 111(R/W) Interrupt coalescing timer period in microseconds. 112Set to 0 to disable. 113.It Va dev.nvme.0.int_coal_threshold 114(R/W) Interrupt coalescing threshold in number of command completions. 115Set to 0 to disable. 116.El 117.Pp 118The following queue pair-level sysctls are currently implemented. 119Admin queue sysctls take the format of dev.nvme.0.adminq and I/O queue sysctls 120take the format of dev.nvme.0.ioq0. 121.Bl -tag -width indent 122.It Va dev.nvme.0.ioq0.num_entries 123(R) Number of entries in this queue pair's command and completion queue. 124.It Va dev.nvme.0.ioq0.num_tr 125(R) Number of nvme_tracker structures currently allocated for this queue pair. 126.It Va dev.nvme.0.ioq0.num_prp_list 127(R) Number of nvme_prp_list structures currently allocated for this queue pair. 128.It Va dev.nvme.0.ioq0.sq_head 129(R) Current location of the submission queue head pointer as observed by 130the driver. 131The head pointer is incremented by the controller as it takes commands off 132of the submission queue. 133.It Va dev.nvme.0.ioq0.sq_tail 134(R) Current location of the submission queue tail pointer as observed by 135the driver. 136The driver increments the tail pointer after writing a command 137into the submission queue to signal that a new command is ready to be 138processed. 139.It Va dev.nvme.0.ioq0.cq_head 140(R) Current location of the completion queue head pointer as observed by 141the driver. 142The driver increments the head pointer after finishing 143with a completion entry that was posted by the controller. 144.It Va dev.nvme.0.ioq0.num_cmds 145(R) Number of commands that have been submitted on this queue pair. 146.It Va dev.nvme.0.ioq0.dump_debug 147(W) Writing 1 to this sysctl will dump the full contents of the submission 148and completion queues to the console. 149.El 150.Sh SEE ALSO 151.Xr nvd 4 , 152.Xr pci 4 , 153.Xr nvmecontrol 8 , 154.Xr disk 9 155.Sh HISTORY 156The 157.Nm 158driver first appeared in 159.Fx 9.2 . 160.Sh AUTHORS 161.An -nosplit 162The 163.Nm 164driver was developed by Intel and originally written by 165.An Jim Harris Aq jimharris@FreeBSD.org , 166with contributions from Joe Golio at EMC. 167.Pp 168This man page was written by 169.An Jim Harris Aq jimharris@FreeBSD.org . 170