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NVME(4)                      Device Drivers Manual                     NVME(4)

     nvme - Non-Volatile Memory Host Controller Interface

     nvme* at pci? dev ? function ?

     The nvme driver provides support for NVMe, or NVM Express, storage
     controllers 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
     operation with the exception of some pass-through commands.

     The driver supports the following features:
              controller and namespace configuration and management using
              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
     vectors 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
     specification allows up to 64k commands per queue, the driver currently
     allocates 1024 entries per queue, or controller maximum, whatever is
     smaller.  Command submissions are done always on the current CPU, the
     command completion 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 command 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.

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

     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,

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

     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.

     At least some Intel nvme adapter cards are known to require PCIe
     Generation 3 slot.  Such cards do not even probe when plugged into older
     generation 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 10.99                    April 27, 2017                    NetBSD 10.99