Re: [PATCH v5 02/21] libnvdimm, nfit: initial libnvdimm infrastructure and NFIT support

["Williams, Dan J" <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

On Wed, 2015-06-03 at 16:57 +0200, Christoph Hellwig wrote:
> On Mon, Jun 01, 2015 at 08:14:19PM -0400, Dan Williams wrote:
> > A libnvdimm bus is the anchor device for registering nvdimm resources and
> > interfaces, for example, a character control device, nvdimm devices,
> > and I/O region devices.  The ACPI NFIT (NVDIMM Firmware Interface Table)
> > is one possible platform description for such non-volatile memory
> > resources in a system.  The nfit.ko driver attaches to the "ACPI0012"
> > device that indicates the presence of the NFIT and parses the table to
> > register a libnvdimm bus instance.
> 
> Havin lib in a name of a bus seems odd.  Why not simply the nvdimm bus?

Sorry, that is a typo the bus is indeed an struct nvdimm_bus instance.

> Also this seems to both have the generic nvdimm infrastructure as well
> as the acpi wiring.  Might make sense to split this into two patches?

I like to show an initial infrastructure consumer with the initial
implementation in one patch.   Makes it easier to catch premature
implementation of features.

> 
> > +config ACPI_NFIT
> > +	tristate "ACPI NVDIMM Firmware Interface Table (NFIT)"
> > +	depends on PHYS_ADDR_T_64BIT
> > +	depends on BLK_DEV
> > +	select NVDIMM_DEVICES
> > +	select LIBNVDIMM
> 
> Is this the right way for the user to chose it?  It seems like enabling
> the NVMDIMM subsystem would be the obvious choice, and ACPI would
> simply enable the table parsing in that case.

The NVDIMM sub-system is enabled by an external provider.  We have the
e820 type-12 provider and the NFIT provider that select LIBNVDIMM.

> > +static u8 nfit_uuid[NFIT_UUID_MAX][16];
> 
> Should this use the uuid_le type?
> 

That would depend on Rafael being open to changing the
acpi_str_to_uuid() prototype to take an uuid_le.

> > +static const char *spa_type_name(u16 type)
> > +{
> > +	switch (type) {
> > +	case NFIT_SPA_VOLATILE: return "volatile";
> > +	case NFIT_SPA_PM: return "pmem";
> > +	case NFIT_SPA_DCR: return "dimm-control-region";
> > +	case NFIT_SPA_BDW: return "block-data-window";
> > +	default: return "unknown";
> 
> Please never put code on the same line as a switch (or goto) label.

Ok, fixed.

> 
> > +static void *add_table(struct acpi_nfit_desc *acpi_desc, void *table, const void *end)
> > +{
> > +	struct device *dev = acpi_desc->dev;
> > +	struct acpi_nfit_header *hdr;
> > +	void *err = ERR_PTR(-ENOMEM);
> > +
> > +	if (table >= end)
> > +		return NULL;
> > +
> > +	hdr = (struct acpi_nfit_header *) table;
> 
> No need to case from void * to another pointer type.

Whoops, fixed.

> 
> > +	switch (hdr->type) {
> > +	case ACPI_NFIT_TYPE_SYSTEM_ADDRESS: {
> > +		struct nfit_spa *nfit_spa = devm_kzalloc(dev, sizeof(*nfit_spa),
> > +				GFP_KERNEL);
> > +		struct acpi_nfit_system_address *spa = table;
> > +
> > +		if (!nfit_spa)
> > +			return err;
> > +		INIT_LIST_HEAD(&nfit_spa->list);
> > +		nfit_spa->spa = spa;
> > +		list_add_tail(&nfit_spa->list, &acpi_desc->spas);
> > +		dev_dbg(dev, "%s: spa index: %d type: %s\n", __func__,
> > +				spa->range_index,
> > +				spa_type_name(nfit_spa_type(spa)));
> 
> If you need local variables inside a switch statement you probably
> want to split each case into a separate helper function.

Yeah, probably better that way. Done.

> 
> > +static inline struct acpi_nfit_memory_map *__to_nfit_memdev(struct nfit_mem *nfit_mem)
> 
> This line is over 80 characters.

I generally don't see the point of fixing up occasional small incursions
over 80 characters if it makes the code more amenable to grep.

> Also why the odd __-prefix?

Later on the series there's a to_nfit_memdev() that takes a struct
device *, and this one is an internal helper.

> 
> > new file mode 100644
> > index 000000000000..24b51dbc8215
> > --- /dev/null
> > +++ b/drivers/nvdimm/Kconfig
> > @@ -0,0 +1,20 @@
> > +menuconfig NVDIMM_DEVICES
> > +	bool "NVDIMM (Non-Volatile Memory Device) Support"
> > +	help
> > +	  Generic support for non-volatile memory devices including
> > +	  ACPI-6-NFIT defined resources.  On platforms that define an
> > +	  NFIT, or otherwise can discover NVDIMM resources, a libnvdimm
> > +	  bus is registered to advertise PMEM (persistent memory)
> > +	  namespaces (/dev/pmemX) and BLK (sliding mmio window(s))
> > +	  namespaces (/dev/ndX). A PMEM namespace refers to a memory
> > +	  resource that may span multiple DIMMs and support DAX (see
> > +	  CONFIG_DAX).  A BLK namespace refers to an NVDIMM control
> > +	  region which exposes an mmio register set for windowed
> > +	  access mode to non-volatile memory.
> > +
> > +if NVDIMM_DEVICES
> > +
> > +config LIBNVDIMM
> > +	tristate
> > +
> > +endif
> 
> What different meanings will CONFIG_NVDIMM_DEVICES and CONFIG_LIBNVDIMM
> have?

Hmm, nothing worthwhile.  I'll merge them into one menuconfig
CONFIG_LIBNVDIMM tristate.

> 
> > diff --git a/drivers/nvdimm/nd-private.h b/drivers/nvdimm/nd-private.h
> > new file mode 100644
> > index 000000000000..e7c4e99a22a4
> > --- /dev/null
> > +++ b/drivers/nvdimm/nd-private.h
> 
> No need for -private if you're already under drivers/nvdimm..

This is the private private-header in the sense that it defines
infrastructure that is only meant for the core.  Drivers (btt, pmem,
blk, etc) must not include nd-private.h.  I'll rename it "nd-core.h" to
make this more clear.

> > +#ifndef __ND_PRIVATE_H__
> > +#define __ND_PRIVATE_H__
> > +#include <linux/libnvdimm.h>
> > +#include <linux/device.h>
> > +
> > +struct nvdimm_bus {
> > +	struct nvdimm_bus_descriptor *nd_desc;
> > +	struct device dev;
> > +	int id;
> > +};
> > +#endif /* __ND_PRIVATE_H__ */
> 
> At least so far this header doesn't need libnvdimm.h

struct nvdimm_bus_descriptor is defined there and a forward declaration
does not make sense since we'll need the rest of the header later in the
series.

> 
> > +#ifndef __LIBNVDIMM_H__
> > +#define __LIBNVDIMM_H__
> > +struct nvdimm;
> > +struct nvdimm_bus_descriptor;
> > +typedef int (*ndctl_fn)(struct nvdimm_bus_descriptor *nd_desc,
> > +		struct nvdimm *nvdimm, unsigned int cmd, void *buf,
> > +		unsigned int buf_len);
> > +
> > +struct nvdimm_bus_descriptor {
> > +	unsigned long dsm_mask;
> > +	char *provider_name;
> > +	ndctl_fn ndctl;
> > +};
> 
> Please provide proper methods that do one thing properly instead of
> ioctl-like multiplexers.

This *is* the ioctl multiplexer.  The generic ioctl implementation in
libnvdimm uses the ndctl_fn to call back out to the provider to process
the command.  In the case of ACPI this maps to a _DSM (device specific
method), for nfit_test it's a emulated implementation, and for
e820-type-12 this is obviously not implemented.


Reflowed patch with these fixes follows...


8<-----
Subject: libnvdimm, nfit: initial libnvdimm infrastructure and NFIT support

From: Dan Williams <dan.j.williams@intel.com>

A libnvdimm bus is the anchor device for registering nvdimm resources and
interfaces, for example, a character control device, nvdimm devices,
and I/O region devices.  The ACPI NFIT (NVDIMM Firmware Interface Table)
is one possible platform description for such non-volatile memory
resources in a system.  The nfit.ko driver attaches to the "ACPI0012"
device that indicates the presence of the NFIT and parses the table to
register a struct nvdimm_bus instance.

Cc: <linux-acpi@vger.kernel.org>
Cc: Lv Zheng <lv.zheng@intel.com>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/Kconfig           |    2 
 drivers/Makefile          |    1 
 drivers/acpi/Kconfig      |   14 +
 drivers/acpi/Makefile     |    1 
 drivers/acpi/nfit.c       |  481 +++++++++++++++++++++++++++++++++++++++++++++
 drivers/acpi/nfit.h       |   89 ++++++++
 drivers/nvdimm/Kconfig    |   13 +
 drivers/nvdimm/Makefile   |    3 
 drivers/nvdimm/core.c     |   67 ++++++
 drivers/nvdimm/nd-core.h  |   23 ++
 include/linux/libnvdimm.h |   34 +++
 11 files changed, 728 insertions(+)
 create mode 100644 drivers/acpi/nfit.c
 create mode 100644 drivers/acpi/nfit.h
 create mode 100644 drivers/nvdimm/Kconfig
 create mode 100644 drivers/nvdimm/Makefile
 create mode 100644 drivers/nvdimm/core.c
 create mode 100644 drivers/nvdimm/nd-core.h
 create mode 100644 include/linux/libnvdimm.h

diff --git a/drivers/Kconfig b/drivers/Kconfig
index c0cc96bab9e7..6e973b8e3a3b 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -182,4 +182,6 @@ source "drivers/thunderbolt/Kconfig"
 
 source "drivers/android/Kconfig"
 
+source "drivers/nvdimm/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 46d2554be404..692adf659028 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -64,6 +64,7 @@ obj-$(CONFIG_FB_INTEL)          += video/fbdev/intelfb/
 
 obj-$(CONFIG_PARPORT)		+= parport/
 obj-y				+= base/ block/ misc/ mfd/ nfc/
+obj-$(CONFIG_LIBNVDIMM)		+= nvdimm/
 obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf/
 obj-$(CONFIG_NUBUS)		+= nubus/
 obj-y				+= macintosh/
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index ab2cbb51c6aa..300b4ef3712b 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -383,6 +383,20 @@ config ACPI_REDUCED_HARDWARE_ONLY
 
 	  If you are unsure what to do, do not enable this option.
 
+config ACPI_NFIT
+	tristate "ACPI NVDIMM Firmware Interface Table (NFIT)"
+	depends on PHYS_ADDR_T_64BIT
+	depends on BLK_DEV
+	select LIBNVDIMM
+	help
+	  Infrastructure to probe ACPI 6 compliant platforms for
+	  NVDIMMs (NFIT) and register a libnvdimm device tree.  In
+	  addition to storage devices this also enables libnvdimm to pass
+	  ACPI._DSM messages for platform/dimm configuration.
+
+	  To compile this driver as a module, choose M here:
+	  the module will be called nfit.
+
 source "drivers/acpi/apei/Kconfig"
 
 config ACPI_EXTLOG
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 8a063e276530..f7e9c92ccdcb 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_ACPI_PCI_SLOT)	+= pci_slot.o
 obj-$(CONFIG_ACPI_PROCESSOR)	+= processor.o
 obj-y				+= container.o
 obj-$(CONFIG_ACPI_THERMAL)	+= thermal.o
+obj-$(CONFIG_ACPI_NFIT)		+= nfit.o
 obj-y				+= acpi_memhotplug.o
 obj-$(CONFIG_ACPI_HOTPLUG_IOAPIC) += ioapic.o
 obj-$(CONFIG_ACPI_BATTERY)	+= battery.o
diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
new file mode 100644
index 000000000000..c400d60018a5
--- /dev/null
+++ b/drivers/acpi/nfit.c
@@ -0,0 +1,481 @@
+/*
+ * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/list_sort.h>
+#include <linux/libnvdimm.h>
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/acpi.h>
+#include "nfit.h"
+
+static u8 nfit_uuid[NFIT_UUID_MAX][16];
+
+static const u8 *to_nfit_uuid(enum nfit_uuids id)
+{
+	return nfit_uuid[id];
+}
+
+static int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc,
+		struct nvdimm *nvdimm, unsigned int cmd, void *buf,
+		unsigned int buf_len)
+{
+	return -ENOTTY;
+}
+
+static const char *spa_type_name(u16 type)
+{
+	static const char *to_name[] = {
+		[NFIT_SPA_VOLATILE] = "volatile",
+		[NFIT_SPA_PM] = "pmem",
+		[NFIT_SPA_DCR] = "dimm-control-region",
+		[NFIT_SPA_BDW] = "block-data-window",
+		[NFIT_SPA_VDISK] = "volatile-disk",
+		[NFIT_SPA_VCD] = "volatile-cd",
+		[NFIT_SPA_PDISK] = "persistent-disk",
+		[NFIT_SPA_PCD] = "persistent-cd",
+
+	};
+
+	if (type > NFIT_SPA_PCD)
+		return "unknown";
+
+	return to_name[type];
+}
+
+static int nfit_spa_type(struct acpi_nfit_system_address *spa)
+{
+	int i;
+
+	for (i = 0; i < NFIT_UUID_MAX; i++)
+		if (memcmp(to_nfit_uuid(i), spa->range_guid, 16) == 0)
+			return i;
+	return -1;
+}
+
+static bool add_spa(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_system_address *spa)
+{
+	struct device *dev = acpi_desc->dev;
+	struct nfit_spa *nfit_spa = devm_kzalloc(dev, sizeof(*nfit_spa),
+			GFP_KERNEL);
+
+	if (!nfit_spa)
+		return false;
+	INIT_LIST_HEAD(&nfit_spa->list);
+	nfit_spa->spa = spa;
+	list_add_tail(&nfit_spa->list, &acpi_desc->spas);
+	dev_dbg(dev, "%s: spa index: %d type: %s\n", __func__,
+			spa->range_index,
+			spa_type_name(nfit_spa_type(spa)));
+	return true;
+}
+
+static bool add_memdev(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_memory_map *memdev)
+{
+	struct device *dev = acpi_desc->dev;
+	struct nfit_memdev *nfit_memdev = devm_kzalloc(dev,
+			sizeof(*nfit_memdev), GFP_KERNEL);
+
+	if (!nfit_memdev)
+		return false;
+	INIT_LIST_HEAD(&nfit_memdev->list);
+	nfit_memdev->memdev = memdev;
+	list_add_tail(&nfit_memdev->list, &acpi_desc->memdevs);
+	dev_dbg(dev, "%s: memdev handle: %#x spa: %d dcr: %d\n",
+			__func__, memdev->device_handle, memdev->range_index,
+			memdev->region_index);
+	return true;
+}
+
+static bool add_dcr(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_control_region *dcr)
+{
+	struct device *dev = acpi_desc->dev;
+	struct nfit_dcr *nfit_dcr = devm_kzalloc(dev, sizeof(*nfit_dcr),
+			GFP_KERNEL);
+
+	if (!nfit_dcr)
+		return false;
+	INIT_LIST_HEAD(&nfit_dcr->list);
+	nfit_dcr->dcr = dcr;
+	list_add_tail(&nfit_dcr->list, &acpi_desc->dcrs);
+	dev_dbg(dev, "%s: dcr index: %d windows: %d\n", __func__,
+			dcr->region_index, dcr->windows);
+	return true;
+}
+
+static bool add_bdw(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_data_region *bdw)
+{
+	struct device *dev = acpi_desc->dev;
+	struct nfit_bdw *nfit_bdw = devm_kzalloc(dev, sizeof(*nfit_bdw),
+			GFP_KERNEL);
+
+	if (!nfit_bdw)
+		return false;
+	INIT_LIST_HEAD(&nfit_bdw->list);
+	nfit_bdw->bdw = bdw;
+	list_add_tail(&nfit_bdw->list, &acpi_desc->bdws);
+	dev_dbg(dev, "%s: bdw dcr: %d windows: %d\n", __func__,
+			bdw->region_index, bdw->windows);
+	return true;
+}
+
+static void *add_table(struct acpi_nfit_desc *acpi_desc, void *table, const void *end)
+{
+	struct device *dev = acpi_desc->dev;
+	struct acpi_nfit_header *hdr;
+	void *err = ERR_PTR(-ENOMEM);
+
+	if (table >= end)
+		return NULL;
+
+	hdr = table;
+	switch (hdr->type) {
+	case ACPI_NFIT_TYPE_SYSTEM_ADDRESS:
+		if (!add_spa(acpi_desc, table))
+			return err;
+		break;
+	case ACPI_NFIT_TYPE_MEMORY_MAP:
+		if (!add_memdev(acpi_desc, table))
+			return err;
+		break;
+	case ACPI_NFIT_TYPE_CONTROL_REGION:
+		if (!add_dcr(acpi_desc, table))
+			return err;
+		break;
+	case ACPI_NFIT_TYPE_DATA_REGION:
+		if (!add_bdw(acpi_desc, table))
+			return err;
+		break;
+	/* TODO */
+	case ACPI_NFIT_TYPE_INTERLEAVE:
+		dev_dbg(dev, "%s: idt\n", __func__);
+		break;
+	case ACPI_NFIT_TYPE_FLUSH_ADDRESS:
+		dev_dbg(dev, "%s: flush\n", __func__);
+		break;
+	case ACPI_NFIT_TYPE_SMBIOS:
+		dev_dbg(dev, "%s: smbios\n", __func__);
+		break;
+	default:
+		dev_err(dev, "unknown table '%d' parsing nfit\n", hdr->type);
+		break;
+	}
+
+	return table + hdr->length;
+}
+
+static void nfit_mem_find_spa_bdw(struct acpi_nfit_desc *acpi_desc,
+		struct nfit_mem *nfit_mem)
+{
+	u32 device_handle = __to_nfit_memdev(nfit_mem)->device_handle;
+	u16 dcr_index = nfit_mem->dcr->region_index;
+	struct nfit_spa *nfit_spa;
+
+	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
+		u16 range_index = nfit_spa->spa->range_index;
+		int type = nfit_spa_type(nfit_spa->spa);
+		struct nfit_memdev *nfit_memdev;
+
+		if (type != NFIT_SPA_BDW)
+			continue;
+
+		list_for_each_entry(nfit_memdev, &acpi_desc->memdevs, list) {
+			if (nfit_memdev->memdev->range_index != range_index)
+				continue;
+			if (nfit_memdev->memdev->device_handle != device_handle)
+				continue;
+			if (nfit_memdev->memdev->region_index != dcr_index)
+				continue;
+
+			nfit_mem->spa_bdw = nfit_spa->spa;
+			return;
+		}
+	}
+
+	dev_dbg(acpi_desc->dev, "SPA-BDW not found for SPA-DCR %d\n",
+			nfit_mem->spa_dcr->range_index);
+	nfit_mem->bdw = NULL;
+}
+
+static int nfit_mem_add(struct acpi_nfit_desc *acpi_desc,
+		struct nfit_mem *nfit_mem, struct acpi_nfit_system_address *spa)
+{
+	u16 dcr_index = __to_nfit_memdev(nfit_mem)->region_index;
+	struct nfit_dcr *nfit_dcr;
+	struct nfit_bdw *nfit_bdw;
+
+	list_for_each_entry(nfit_dcr, &acpi_desc->dcrs, list) {
+		if (nfit_dcr->dcr->region_index != dcr_index)
+			continue;
+		nfit_mem->dcr = nfit_dcr->dcr;
+		break;
+	}
+
+	if (!nfit_mem->dcr) {
+		dev_dbg(acpi_desc->dev, "SPA %d missing:%s%s\n", spa->range_index,
+				__to_nfit_memdev(nfit_mem) ? "" : " MEMDEV",
+				nfit_mem->dcr ? "" : " DCR");
+		return -ENODEV;
+	}
+
+	/*
+	 * We've found enough to create an nvdimm, optionally
+	 * find an associated BDW
+	 */
+	list_add(&nfit_mem->list, &acpi_desc->dimms);
+
+	list_for_each_entry(nfit_bdw, &acpi_desc->bdws, list) {
+		if (nfit_bdw->bdw->region_index != dcr_index)
+			continue;
+		nfit_mem->bdw = nfit_bdw->bdw;
+		break;
+	}
+
+	if (!nfit_mem->bdw)
+		return 0;
+
+	nfit_mem_find_spa_bdw(acpi_desc, nfit_mem);
+	return 0;
+}
+
+static int nfit_mem_dcr_init(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_system_address *spa)
+{
+	struct nfit_mem *nfit_mem, *found;
+	struct nfit_memdev *nfit_memdev;
+	int type = nfit_spa_type(spa);
+	u16 dcr_index;
+
+	switch (type) {
+	case NFIT_SPA_DCR:
+	case NFIT_SPA_PM:
+		break;
+	default:
+		return 0;
+	}
+
+	list_for_each_entry(nfit_memdev, &acpi_desc->memdevs, list) {
+		int rc;
+
+		if (nfit_memdev->memdev->range_index != spa->range_index)
+			continue;
+		found = NULL;
+		dcr_index = nfit_memdev->memdev->region_index;
+		list_for_each_entry(nfit_mem, &acpi_desc->dimms, list)
+			if (__to_nfit_memdev(nfit_mem)->region_index == dcr_index) {
+				found = nfit_mem;
+				break;
+			}
+
+		if (found)
+			nfit_mem = found;
+		else {
+			nfit_mem = devm_kzalloc(acpi_desc->dev,
+					sizeof(*nfit_mem), GFP_KERNEL);
+			if (!nfit_mem)
+				return -ENOMEM;
+			INIT_LIST_HEAD(&nfit_mem->list);
+		}
+
+		if (type == NFIT_SPA_DCR) {
+			/* multiple dimms may share a SPA when interleaved */
+			nfit_mem->spa_dcr = spa;
+			nfit_mem->memdev_dcr = nfit_memdev->memdev;
+		} else {
+			/*
+			 * A single dimm may belong to multiple SPA-PM
+			 * ranges, record at least one in addition to
+			 * any SPA-DCR range.
+			 */
+			nfit_mem->memdev_pmem = nfit_memdev->memdev;
+		}
+
+		if (found)
+			continue;
+
+		rc = nfit_mem_add(acpi_desc, nfit_mem, spa);
+		if (rc)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int nfit_mem_cmp(void *priv, struct list_head *__a, struct list_head *__b)
+{
+	struct nfit_mem *a = container_of(__a, typeof(*a), list);
+	struct nfit_mem *b = container_of(__b, typeof(*b), list);
+	u32 handleA, handleB;
+
+	handleA = __to_nfit_memdev(a)->device_handle;
+	handleB = __to_nfit_memdev(b)->device_handle;
+	if (handleA < handleB)
+		return -1;
+	else if (handleA > handleB)
+		return 1;
+	return 0;
+}
+
+static int nfit_mem_init(struct acpi_nfit_desc *acpi_desc)
+{
+	struct nfit_spa *nfit_spa;
+
+	/*
+	 * For each SPA-DCR or SPA-PMEM address range find its
+	 * corresponding MEMDEV(s).  From each MEMDEV find the
+	 * corresponding DCR.  Then, if we're operating on a SPA-DCR,
+	 * try to find a SPA-BDW and a corresponding BDW that references
+	 * the DCR.  Throw it all into an nfit_mem object.  Note, that
+	 * BDWs are optional.
+	 */
+	list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
+		int rc;
+
+		rc = nfit_mem_dcr_init(acpi_desc, nfit_spa->spa);
+		if (rc)
+			return rc;
+	}
+
+	list_sort(NULL, &acpi_desc->dimms, nfit_mem_cmp);
+
+	return 0;
+}
+
+static int acpi_nfit_init(struct acpi_nfit_desc *acpi_desc, acpi_size sz)
+{
+	struct device *dev = acpi_desc->dev;
+	const void *end;
+	u8 *data;
+
+	INIT_LIST_HEAD(&acpi_desc->spas);
+	INIT_LIST_HEAD(&acpi_desc->dcrs);
+	INIT_LIST_HEAD(&acpi_desc->bdws);
+	INIT_LIST_HEAD(&acpi_desc->memdevs);
+	INIT_LIST_HEAD(&acpi_desc->dimms);
+
+	data = (u8 *) acpi_desc->nfit;
+	end = data + sz;
+	data += sizeof(struct acpi_table_nfit);
+	while (!IS_ERR_OR_NULL(data))
+		data = add_table(acpi_desc, data, end);
+
+	if (IS_ERR(data)) {
+		dev_dbg(dev, "%s: nfit table parsing error: %ld\n", __func__,
+				PTR_ERR(data));
+		return PTR_ERR(data);
+	}
+
+	if (nfit_mem_init(acpi_desc) != 0)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int acpi_nfit_add(struct acpi_device *adev)
+{
+	struct nvdimm_bus_descriptor *nd_desc;
+	struct acpi_nfit_desc *acpi_desc;
+	struct device *dev = &adev->dev;
+	struct acpi_table_header *tbl;
+	acpi_status status = AE_OK;
+	acpi_size sz;
+	int rc;
+
+	status = acpi_get_table_with_size("NFIT", 0, &tbl, &sz);
+	if (ACPI_FAILURE(status)) {
+		dev_err(dev, "failed to find NFIT\n");
+		return -ENXIO;
+	}
+
+	acpi_desc = devm_kzalloc(dev, sizeof(*acpi_desc), GFP_KERNEL);
+	if (!acpi_desc)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, acpi_desc);
+	acpi_desc->dev = dev;
+	acpi_desc->nfit = (struct acpi_table_nfit *) tbl;
+	nd_desc = &acpi_desc->nd_desc;
+	nd_desc->provider_name = "ACPI.NFIT";
+	nd_desc->ndctl = acpi_nfit_ctl;
+
+	acpi_desc->nvdimm_bus = nvdimm_bus_register(dev, nd_desc);
+	if (!acpi_desc->nvdimm_bus)
+		return -ENXIO;
+
+	rc = acpi_nfit_init(acpi_desc, sz);
+	if (rc) {
+		nvdimm_bus_unregister(acpi_desc->nvdimm_bus);
+		return rc;
+	}
+	return 0;
+}
+
+static int acpi_nfit_remove(struct acpi_device *adev)
+{
+	struct acpi_nfit_desc *acpi_desc = dev_get_drvdata(&adev->dev);
+
+	nvdimm_bus_unregister(acpi_desc->nvdimm_bus);
+	return 0;
+}
+
+static const struct acpi_device_id acpi_nfit_ids[] = {
+	{ "ACPI0012", 0 },
+	{ "", 0 },
+};
+MODULE_DEVICE_TABLE(acpi, acpi_nfit_ids);
+
+static struct acpi_driver acpi_nfit_driver = {
+	.name = KBUILD_MODNAME,
+	.ids = acpi_nfit_ids,
+	.flags = ACPI_DRIVER_ALL_NOTIFY_EVENTS,
+	.ops = {
+		.add = acpi_nfit_add,
+		.remove = acpi_nfit_remove,
+	},
+};
+
+static __init int nfit_init(void)
+{
+	BUILD_BUG_ON(sizeof(struct acpi_table_nfit) != 40);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_system_address) != 56);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_memory_map) != 48);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_interleave) != 20);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_smbios) != 9);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_control_region) != 80);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_data_region) != 40);
+
+	acpi_str_to_uuid(UUID_VOLATILE_MEMORY, nfit_uuid[NFIT_SPA_VOLATILE]);
+	acpi_str_to_uuid(UUID_PERSISTENT_MEMORY, nfit_uuid[NFIT_SPA_PM]);
+	acpi_str_to_uuid(UUID_CONTROL_REGION, nfit_uuid[NFIT_SPA_DCR]);
+	acpi_str_to_uuid(UUID_DATA_REGION, nfit_uuid[NFIT_SPA_BDW]);
+	acpi_str_to_uuid(UUID_VOLATILE_VIRTUAL_DISK, nfit_uuid[NFIT_SPA_VDISK]);
+	acpi_str_to_uuid(UUID_VOLATILE_VIRTUAL_CD, nfit_uuid[NFIT_SPA_VCD]);
+	acpi_str_to_uuid(UUID_PERSISTENT_VIRTUAL_DISK, nfit_uuid[NFIT_SPA_PDISK]);
+	acpi_str_to_uuid(UUID_PERSISTENT_VIRTUAL_CD, nfit_uuid[NFIT_SPA_PCD]);
+	acpi_str_to_uuid(UUID_NFIT_BUS, nfit_uuid[NFIT_DEV_BUS]);
+	acpi_str_to_uuid(UUID_NFIT_DIMM, nfit_uuid[NFIT_DEV_DIMM]);
+
+	return acpi_bus_register_driver(&acpi_nfit_driver);
+}
+
+static __exit void nfit_exit(void)
+{
+	acpi_bus_unregister_driver(&acpi_nfit_driver);
+}
+
+module_init(nfit_init);
+module_exit(nfit_exit);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
new file mode 100644
index 000000000000..2d98cc1b7b6c
--- /dev/null
+++ b/drivers/acpi/nfit.h
@@ -0,0 +1,89 @@
+/*
+ * NVDIMM Firmware Interface Table - NFIT
+ *
+ * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#ifndef __NFIT_H__
+#define __NFIT_H__
+#include <linux/libnvdimm.h>
+#include <linux/types.h>
+#include <linux/uuid.h>
+#include <linux/acpi.h>
+#include <acpi/acuuid.h>
+
+#define UUID_NFIT_BUS "2f10e7a4-9e91-11e4-89d3-123b93f75cba"
+#define UUID_NFIT_DIMM "4309ac30-0d11-11e4-9191-0800200c9a66"
+
+enum nfit_uuids {
+	NFIT_SPA_VOLATILE,
+	NFIT_SPA_PM,
+	NFIT_SPA_DCR,
+	NFIT_SPA_BDW,
+	NFIT_SPA_VDISK,
+	NFIT_SPA_VCD,
+	NFIT_SPA_PDISK,
+	NFIT_SPA_PCD,
+	NFIT_DEV_BUS,
+	NFIT_DEV_DIMM,
+	NFIT_UUID_MAX,
+};
+
+struct nfit_spa {
+	struct acpi_nfit_system_address *spa;
+	struct list_head list;
+};
+
+struct nfit_dcr {
+	struct acpi_nfit_control_region *dcr;
+	struct list_head list;
+};
+
+struct nfit_bdw {
+	struct acpi_nfit_data_region *bdw;
+	struct list_head list;
+};
+
+struct nfit_memdev {
+	struct acpi_nfit_memory_map *memdev;
+	struct list_head list;
+};
+
+/* assembled tables for a given dimm/memory-device */
+struct nfit_mem {
+	struct acpi_nfit_memory_map *memdev_dcr;
+	struct acpi_nfit_memory_map *memdev_pmem;
+	struct acpi_nfit_control_region *dcr;
+	struct acpi_nfit_data_region *bdw;
+	struct acpi_nfit_system_address *spa_dcr;
+	struct acpi_nfit_system_address *spa_bdw;
+	struct list_head list;
+};
+
+struct acpi_nfit_desc {
+	struct nvdimm_bus_descriptor nd_desc;
+	struct acpi_table_nfit *nfit;
+	struct list_head memdevs;
+	struct list_head dimms;
+	struct list_head spas;
+	struct list_head dcrs;
+	struct list_head bdws;
+	struct nvdimm_bus *nvdimm_bus;
+	struct device *dev;
+};
+
+static inline struct acpi_nfit_memory_map *__to_nfit_memdev(struct nfit_mem *nfit_mem)
+{
+	if (nfit_mem->memdev_dcr)
+		return nfit_mem->memdev_dcr;
+	return nfit_mem->memdev_pmem;
+}
+#endif /* __NFIT_H__ */
diff --git a/drivers/nvdimm/Kconfig b/drivers/nvdimm/Kconfig
new file mode 100644
index 000000000000..4f2291938ea0
--- /dev/null
+++ b/drivers/nvdimm/Kconfig
@@ -0,0 +1,13 @@
+config LIBNVDIMM
+	tristate "NVDIMM (Non-Volatile Memory Device) Support"
+	help
+	  Generic support for non-volatile memory devices including
+	  ACPI-6-NFIT defined resources.  On platforms that define an
+	  NFIT, or otherwise can discover NVDIMM resources, a libnvdimm
+	  bus is registered to advertise PMEM (persistent memory)
+	  namespaces (/dev/pmemX) and BLK (sliding mmio window(s))
+	  namespaces (/dev/ndX). A PMEM namespace refers to a memory
+	  resource that may span multiple DIMMs and support DAX (see
+	  CONFIG_DAX).  A BLK namespace refers to an NVDIMM control
+	  region which exposes an mmio register set for windowed
+	  access mode to non-volatile memory.
diff --git a/drivers/nvdimm/Makefile b/drivers/nvdimm/Makefile
new file mode 100644
index 000000000000..10bc7af47992
--- /dev/null
+++ b/drivers/nvdimm/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_LIBNVDIMM) += libnvdimm.o
+
+libnvdimm-y := core.o
diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c
new file mode 100644
index 000000000000..5ccd500ffd4f
--- /dev/null
+++ b/drivers/nvdimm/core.c
@@ -0,0 +1,67 @@
+/*
+ * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/libnvdimm.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include "nd-core.h"
+
+static DEFINE_IDA(nd_ida);
+
+static void nvdimm_bus_release(struct device *dev)
+{
+	struct nvdimm_bus *nvdimm_bus = container_of(dev, struct nvdimm_bus, dev);
+
+	ida_simple_remove(&nd_ida, nvdimm_bus->id);
+	kfree(nvdimm_bus);
+}
+
+struct nvdimm_bus *nvdimm_bus_register(struct device *parent,
+		struct nvdimm_bus_descriptor *nd_desc)
+{
+	struct nvdimm_bus *nvdimm_bus = kzalloc(sizeof(*nvdimm_bus), GFP_KERNEL);
+	int rc;
+
+	if (!nvdimm_bus)
+		return NULL;
+	nvdimm_bus->id = ida_simple_get(&nd_ida, 0, 0, GFP_KERNEL);
+	if (nvdimm_bus->id < 0) {
+		kfree(nvdimm_bus);
+		return NULL;
+	}
+	nvdimm_bus->nd_desc = nd_desc;
+	nvdimm_bus->dev.parent = parent;
+	nvdimm_bus->dev.release = nvdimm_bus_release;
+	dev_set_name(&nvdimm_bus->dev, "ndbus%d", nvdimm_bus->id);
+	rc = device_register(&nvdimm_bus->dev);
+	if (rc) {
+		dev_dbg(&nvdimm_bus->dev, "device registration failed: %d\n", rc);
+		put_device(&nvdimm_bus->dev);
+		return NULL;
+	}
+
+	return nvdimm_bus;
+}
+EXPORT_SYMBOL_GPL(nvdimm_bus_register);
+
+void nvdimm_bus_unregister(struct nvdimm_bus *nvdimm_bus)
+{
+	if (!nvdimm_bus)
+		return;
+	device_unregister(&nvdimm_bus->dev);
+}
+EXPORT_SYMBOL_GPL(nvdimm_bus_unregister);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Intel Corporation");
diff --git a/drivers/nvdimm/nd-core.h b/drivers/nvdimm/nd-core.h
new file mode 100644
index 000000000000..e7c4e99a22a4
--- /dev/null
+++ b/drivers/nvdimm/nd-core.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#ifndef __ND_PRIVATE_H__
+#define __ND_PRIVATE_H__
+#include <linux/libnvdimm.h>
+#include <linux/device.h>
+
+struct nvdimm_bus {
+	struct nvdimm_bus_descriptor *nd_desc;
+	struct device dev;
+	int id;
+};
+#endif /* __ND_PRIVATE_H__ */
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
new file mode 100644
index 000000000000..2b3c63950c91
--- /dev/null
+++ b/include/linux/libnvdimm.h
@@ -0,0 +1,34 @@
+/*
+ * libnvdimm - Non-volatile-memory Devices Subsystem
+ *
+ * Copyright(c) 2013-2015 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#ifndef __LIBNVDIMM_H__
+#define __LIBNVDIMM_H__
+struct nvdimm;
+struct nvdimm_bus_descriptor;
+typedef int (*ndctl_fn)(struct nvdimm_bus_descriptor *nd_desc,
+		struct nvdimm *nvdimm, unsigned int cmd, void *buf,
+		unsigned int buf_len);
+
+struct nvdimm_bus_descriptor {
+	unsigned long dsm_mask;
+	char *provider_name;
+	ndctl_fn ndctl;
+};
+
+struct device;
+struct nvdimm_bus;
+struct nvdimm_bus *nvdimm_bus_register(struct device *parent,
+		struct nvdimm_bus_descriptor *nfit_desc);
+void nvdimm_bus_unregister(struct nvdimm_bus *nvdimm_bus);
+#endif /* __LIBNVDIMM_H__ */