1.\" 2.\" Copyright (c) 2012-2014 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 March 18, 2014 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 which can be 58partitioned. 59Note that in NVM Express terms, a namespace is roughly equivalent to a 60SCSI LUN. 61.Sh DESCRIPTION 62The 63.Nm 64driver provides support for NVM Express (NVMe) controllers, such as: 65.Bl -bullet 66.It 67Hardware initialization 68.It 69Per-CPU IO queue pairs 70.It 71API for registering NVMe namespace consumers such as 72.Xr nvd 4 73.It 74API for submitting NVM commands to namespaces 75.It 76Ioctls for controller and namespace configuration and management 77.El 78.Pp 79The 80.Nm 81driver creates controller device nodes in the format 82.Pa /dev/nvmeX 83and namespace device nodes in 84the format 85.Pa /dev/nvmeXnsY . 86Note that the NVM Express specification starts numbering namespaces at 1, 87not 0, and this driver follows that convention. 88.El 89.Sh CONFIGURATION 90By default, 91.Nm 92will create an I/O queue pair for each CPU, provided enough MSI-X vectors 93can be allocated. 94To force a single I/O queue pair shared by all CPUs, set the following 95tunable value in 96.Xr loader.conf 5 : 97.Bd -literal -offset indent 98hw.nvme.per_cpu_io_queues=0 99.Ed 100.Pp 101To force legacy interrupts for all 102.Nm 103driver instances, set the following tunable value in 104.Xr loader.conf 5 : 105.Bd -literal -offset indent 106hw.nvme.force_intx=1 107.Ed 108.Pp 109Note that use of INTx implies disabling of per-CPU I/O queue pairs. 110.Sh SYSCTL VARIABLES 111The following controller-level sysctls are currently implemented: 112.Bl -tag -width indent 113.It Va dev.nvme.0.int_coal_time 114(R/W) Interrupt coalescing timer period in microseconds. 115Set to 0 to disable. 116.It Va dev.nvme.0.int_coal_threshold 117(R/W) Interrupt coalescing threshold in number of command completions. 118Set to 0 to disable. 119.El 120.Pp 121The following queue pair-level sysctls are currently implemented. 122Admin queue sysctls take the format of dev.nvme.0.adminq and I/O queue sysctls 123take the format of dev.nvme.0.ioq0. 124.Bl -tag -width indent 125.It Va dev.nvme.0.ioq0.num_entries 126(R) Number of entries in this queue pair's command and completion queue. 127.It Va dev.nvme.0.ioq0.num_tr 128(R) Number of nvme_tracker structures currently allocated for this queue pair. 129.It Va dev.nvme.0.ioq0.num_prp_list 130(R) Number of nvme_prp_list structures currently allocated for this queue pair. 131.It Va dev.nvme.0.ioq0.sq_head 132(R) Current location of the submission queue head pointer as observed by 133the driver. 134The head pointer is incremented by the controller as it takes commands off 135of the submission queue. 136.It Va dev.nvme.0.ioq0.sq_tail 137(R) Current location of the submission queue tail pointer as observed by 138the driver. 139The driver increments the tail pointer after writing a command 140into the submission queue to signal that a new command is ready to be 141processed. 142.It Va dev.nvme.0.ioq0.cq_head 143(R) Current location of the completion queue head pointer as observed by 144the driver. 145The driver increments the head pointer after finishing 146with a completion entry that was posted by the controller. 147.It Va dev.nvme.0.ioq0.num_cmds 148(R) Number of commands that have been submitted on this queue pair. 149.It Va dev.nvme.0.ioq0.dump_debug 150(W) Writing 1 to this sysctl will dump the full contents of the submission 151and completion queues to the console. 152.El 153.Sh SEE ALSO 154.Xr nvd 4 , 155.Xr pci 4 , 156.Xr nvmecontrol 8 , 157.Xr disk 9 158.Sh HISTORY 159The 160.Nm 161driver first appeared in 162.Fx 9.2 . 163.Sh AUTHORS 164.An -nosplit 165The 166.Nm 167driver was developed by Intel and originally written by 168.An Jim Harris Aq jimharris@FreeBSD.org , 169with contributions from Joe Golio at EMC. 170.Pp 171This man page was written by 172.An Jim Harris Aq jimharris@FreeBSD.org . 173