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NVME(4) NetBSD Kernel Interfaces Manual NVME(4)
Powered by man-cgi (2021-06-01).
Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
nvme -- Non-Volatile Memory Host Controller Interface
nvme* at pci? dev ? function ?
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
· 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.
/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 <firstname.lastname@example.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 Genera-
tion 3 slot. Such cards do not even probe when plugged into older gener-
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 9.0 April 27, 2017 NetBSD 9.0