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.\" Copyright (c) 2019 The FreeBSD Foundation, Inc.
.\"
.\" This documentation was written by
.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
.\" from the FreeBSD Foundation.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd September 5, 2019
.Dt NVDIMM 4
.Os
.Sh NAME
.Nm nvdimm
.Nd ACPI NVDIMM driver
.Sh SYNOPSIS
To load the driver as a module at boot, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
nvdimm_load="YES"
.Ed
.Sh DESCRIPTION
.Bf -symbolic
Note:
The
.Nm
driver is under development and has some important limitations
described below.
.Ef
.Pp
The
.Nm
driver provides access to Non-Volatile DIMM (NVDIMM) persistent memory
devices, which are ACPI-enumerated under the root NVDIMM device
with a
.Va _HID
of
.Dv ACPI0012
and in the
.Dv NFIT
table.
.Pp
For each System Physical Address (SPA) Range described by NFIT, a
device node
.Pa /dev/nvdimm_spaNNN
is created, where
.Dv NNN
is the SPA position in the table.
The node can be used to
.Xr read 2 ,
.Xr write 2 ,
or
.Xr mmap 2
the device.
.Pp
Also, for each SPA, the geom provider
.Pa spaNNN
is created, which can be used to create a conventional filesystem (e.g.,
by
.Xr newfs 8 )
and
.Xr mount 8
it as any storage volume.
Content accessible by
.Pa /dev/nvdimm_spaNNN
and
.Pa /dev/spaNNN
is coherent.
.Pp
The
.Nm
driver has support for reading NVDIMM namespaces (if supported by your
hardware and already configured by some other mechanism, e.g., a BIOS
configuration screen).
The driver will provide a
.Pa /dev/nvdimm_spaNNNnsMMM
device node and
.Pa spaNNNnsMMM
geom provider for each namespace in a SPA, which behave analogously to their
full-SPA cousins described above.
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr GEOM 4 ,
.Xr geom 8 ,
.Xr mount 8 ,
.Xr newfs 8 ,
.Xr disk 9
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 12.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was originally written by
.An Konstantin Belousov Aq Mt kib@FreeBSD.org ,
and then updated by
.An D. Scott Phillips Aq Mt scottph@FreeBSD.org .
.Sh BUGS
The
.Nm
driver does not utilize the Block Window interface, so if a write to an
NVDIMM is interrupted due to a system crash or power outage,
the corresponding page might be left in a partially updated state.
.Pp
There is no support for Device-Specific Methods (DSM), used to report and
control device health and wearing.
.Pp
The driver depends on the
.Xr pmap_largemap 9
pmap interface, which is currently only implemented on amd64.
The interface can be only reasonable implemented on 64bit architectures.
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