nvme(4) - NetBSD Manual Pages

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NVME(4)                 NetBSD Kernel Interfaces Manual                NVME(4)


NAME

     nvme -- Non-Volatile Memory Host Controller Interface


SYNOPSIS

     nvme* at pci? dev ? function ?


DESCRIPTION

     The nvme driver provides support for NVMe, or NVM Express, storage con-
     trollers conforming to the Non-Volatile Memory Host Controller Interface
     specification.  Controllers complying to specification version 1.1 and
     1.2 are known to work.  Other versions should work too for normal opera-
     tion with the exception of some pass-through commands.

     The driver supports the following features:
           ·   controller and namespace configuration and management using
               nvmectl(8)
           ·   highly parallel I/O using per-CPU I/O queues
           ·   PCI MSI/MSI-X attachment, and INTx for legacy systems

     On systems supporting MSI/MSI-X, the nvme driver uses per-CPU IO queue
     pairs for lockless and highly parallelized I/O.  Interrupt handlers are
     scheduled on distinct CPUs.  The driver allocates as many interrupt vec-
     tors as available, up to number of CPUs + 1.  MSI supports up to 32
     interrupt vectors within the system, MSI-X can have up to 2k.  Each I/O
     queue pair has a separate command circular buffer.  The nvme specifica-
     tion allows up to 64k commands per queue, the driver currently allocates
     1024 entries per queue, or controller maximum, whatever is smaller.  Com-
     mand submissions are done always on the current CPU, the command comple-
     tion interrupt is handled on the CPU corresponding to the I/O queue ID -
     first I/O queue on CPU0, second I/O queue on CPU1, etc.  Admin queue com-
     mand completion is handled by CPU0 by default.  To keep lock contention
     to minimum, it is recommended to keep this assignment, even though it is
     possible to reassign the interrupt handlers differently using intrctl(8).

     On systems without MSI, the driver uses a single HW interrupt handler for
     both admin and standard I/O commands.  Command submissions are done on
     the current CPU, the command completion interrupt is handled on CPU0 by
     default.  This leads to some lock contention, especially on command ccbs.

     The driver offloads command completion processing to soft interrupt, in
     order to increase the total system I/O capacity and throughput.


FILES

     /dev/nvme*  nvme device special files used by nvmectl(8).


SEE ALSO

     intro(4), ld(4), pci(4), intrctl(8), MAKEDEV(8), nvmectl(8)

     NVM Express, Inc., NVM Express - scalable, efficient, and industry
     standard, http://nvmexpress.org/, 2016-06-12.

     NVM Express, Inc., NVM Express Revision 1.2.1,
     http://www.nvmexpress.org/wp-
     content/uploads/NVM_Express_1_2_1_Gold_20160603.pdf, 2016-06-05.


HISTORY

     The nvme driver first appeared in OpenBSD 6.0 and in NetBSD 8.0.


AUTHORS

     The nvme driver was written by David Gwynne <dlg@openbsd.org> for OpenBSD
     and ported to NetBSD by NONAKA Kimihiro <nonaka@NetBSD.org>.  Jaromir
     Dolecek <jdolecek@NetBSD.org> contributed to making this driver MPSAFE.


NOTES

     At least some Intel nvme adapter cards are known to require PCIe Genera-
     tion 3 slot.  Such cards do not even probe when plugged into older gener-
     ation slot.

     The driver was also tested and confirmed working fine for emulated nvme
     devices under QEMU 2.8.0 and Oracle VirtualBox 5.1.20.

NetBSD 8.0                      April 27, 2017                      NetBSD 8.0