ND: NFIT-Defined / NVDIMM Subsystem

Since 2010 Intel has included non-volatile memory support on a few
storage-focused platforms with a feature named ADR (Asynchronous DRAM
Refresh).  These platforms were mostly targeted at custom applications
and never enjoyed standard discovery mechanisms for platform firmware
to advertise non-volatile memory capabilities. This now changes with
the publication of version 6 of the ACPI specification [1] and its
inclusion of a new table for describing platform memory capabilities.
The NVDIMM Firmware Interface Table (NFIT), along with new EFI and E820
memory types, enumerates persistent memory ranges, memory-mapped-I/O
apertures, physical memory devices (DIMMs), and their associated
properties.

The ND-subsystem wraps a Linux device driver model around the objects
and address boundaries defined in the specification and introduces 3 new
drivers.

  nd_pmem: NFIT enabled version of the existing 'pmem' driver [2]
  nd_blk: mmio aperture method for accessing persistent storage
  nd_btt: give persistent memory disk semantics (atomic sector update)

See the documentation in patch2 for more details, and there is
supplemental documentation on pmem.io [4].  Please review, and
patches welcome...

For kicking the tires, this release is accompanied by a userspace
management library 'ndctl' that includes unit tests (make check) for all
of the kernel ABIs.  The nfit_test.ko module can be used to explore a
sample NFIT topology.

[1]: http://www.uefi.org/sites/default/files/resources/ACPI_6....
[2]: https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/...
[3]: https://github.com/pmem/ndctl
[4]: http://pmem.io/documents/

--
Dan for the NFIT driver development team Andy Rudoff, Matthew Wilcox, Ross
Zwisler, and Vishal Verma
Original Source: https://lwn.net/Articles/640891/
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