Merge tag 'devdax-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull device-dax updates from Dan Williams:
 "New device-dax infrastructure to allow persistent memory and other
  "reserved" / performance differentiated memories, to be assigned to
  the core-mm as "System RAM".

  Some users want to use persistent memory as additional volatile
  memory. They are willing to cope with potential performance
  differences, for example between DRAM and 3D Xpoint, and want to use
  typical Linux memory management apis rather than a userspace memory
  allocator layered over an mmap() of a dax file. The administration
  model is to decide how much Persistent Memory (pmem) to use as System
  RAM, create a device-dax-mode namespace of that size, and then assign
  it to the core-mm. The rationale for device-dax is that it is a
  generic memory-mapping driver that can be layered over any "special
  purpose" memory, not just pmem. On subsequent boots udev rules can be
  used to restore the memory assignment.

  One implication of using pmem as RAM is that mlock() no longer keeps
  data off persistent media. For this reason it is recommended to enable
  NVDIMM Security (previously merged for 5.0) to encrypt pmem contents
  at rest. We considered making this recommendation an actively enforced
  requirement, but in the end decided to leave it as a distribution /
  administrator policy to allow for emulation and test environments that
  lack security capable NVDIMMs.

  Summary:

   - Replace the /sys/class/dax device model with /sys/bus/dax, and
     include a compat driver so distributions can opt-in to the new ABI.

   - Allow for an alternative driver for the device-dax address-range

   - Introduce the 'kmem' driver to hotplug / assign a device-dax
     address-range to the core-mm.

   - Arrange for the device-dax target-node to be onlined so that the
     newly added memory range can be uniquely referenced by numa apis"

NOTE! I'm not entirely happy with the whole "PMEM as RAM" model because
we currently have special - and very annoying rules in the kernel about
accessing PMEM only with the "MC safe" accessors, because machine checks
inside the regular repeat string copy functions can be fatal in some
(not described) circumstances.

And apparently the PMEM modules can cause that a lot more than regular
RAM.  The argument is that this happens because PMEM doesn't necessarily
get scrubbed at boot like RAM does, but that is planned to be added for
the user space tooling.

Quoting Dan from another email:
 "The exposure can be reduced in the volatile-RAM case by scanning for
  and clearing errors before it is onlined as RAM. The userspace tooling
  for that can be in place before v5.1-final. There's also runtime
  notifications of errors via acpi_nfit_uc_error_notify() from
  background scrubbers on the DIMM devices. With that mechanism the
  kernel could proactively clear newly discovered poison in the volatile
  case, but that would be additional development more suitable for v5.2.

  I understand the concern, and the need to highlight this issue by
  tapping the brakes on feature development, but I don't see PMEM as RAM
  making the situation worse when the exposure is also there via DAX in
  the PMEM case. Volatile-RAM is arguably a safer use case since it's
  possible to repair pages where the persistent case needs active
  application coordination"

* tag 'devdax-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  device-dax: "Hotplug" persistent memory for use like normal RAM
  mm/resource: Let walk_system_ram_range() search child resources
  mm/memory-hotplug: Allow memory resources to be children
  mm/resource: Move HMM pr_debug() deeper into resource code
  mm/resource: Return real error codes from walk failures
  device-dax: Add a 'modalias' attribute to DAX 'bus' devices
  device-dax: Add a 'target_node' attribute
  device-dax: Auto-bind device after successful new_id
  acpi/nfit, device-dax: Identify differentiated memory with a unique numa-node
  device-dax: Add /sys/class/dax backwards compatibility
  device-dax: Add support for a dax override driver
  device-dax: Move resource pinning+mapping into the common driver
  device-dax: Introduce bus + driver model
  device-dax: Start defining a dax bus model
  device-dax: Remove multi-resource infrastructure
  device-dax: Kill dax_region base
  device-dax: Kill dax_region ida

22 files changed, 1044 insertions, 502 deletions

diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
index df8979008dd4..5a389a4f4f65 100644
--- a/drivers/acpi/nfit/core.c
+++ b/drivers/acpi/nfit/core.c
@@ -2956,11 +2956,15 @@ static int acpi_nfit_register_region(struct acpi_nfit_desc *acpi_desc,
 	ndr_desc->res = &res;
 	ndr_desc->provider_data = nfit_spa;
 	ndr_desc->attr_groups = acpi_nfit_region_attribute_groups;
-	if (spa->flags & ACPI_NFIT_PROXIMITY_VALID)
+	if (spa->flags & ACPI_NFIT_PROXIMITY_VALID) {
 		ndr_desc->numa_node = acpi_map_pxm_to_online_node(
 						spa->proximity_domain);
-	else
+		ndr_desc->target_node = acpi_map_pxm_to_node(
+				spa->proximity_domain);
+	} else {
 		ndr_desc->numa_node = NUMA_NO_NODE;
+		ndr_desc->target_node = NUMA_NO_NODE;
+	}
 
 	/*
 	 * Persistence domain bits are hierarchical, if
diff --git a/drivers/acpi/numa.c b/drivers/acpi/numa.c
index 7bbbf8256a41..867f6e3f2b4f 100644
--- a/drivers/acpi/numa.c
+++ b/drivers/acpi/numa.c
@@ -84,6 +84,7 @@ int acpi_map_pxm_to_node(int pxm)
 
 	return node;
 }
+EXPORT_SYMBOL(acpi_map_pxm_to_node);
 
 /**
  * acpi_map_pxm_to_online_node - Map proximity ID to online node
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 048cbf7d5233..cb8347500ce2 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -88,6 +88,7 @@ unsigned long __weak memory_block_size_bytes(void)
 {
 	return MIN_MEMORY_BLOCK_SIZE;
 }
+EXPORT_SYMBOL_GPL(memory_block_size_bytes);
 
 static unsigned long get_memory_block_size(void)
 {
diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index e0700bf4893a..5ef624fe3934 100644
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -23,12 +23,38 @@ config DEV_DAX
 config DEV_DAX_PMEM
 	tristate "PMEM DAX: direct access to persistent memory"
 	depends on LIBNVDIMM && NVDIMM_DAX && DEV_DAX
+	depends on m # until we can kill DEV_DAX_PMEM_COMPAT
 	default DEV_DAX
 	help
 	  Support raw access to persistent memory.  Note that this
 	  driver consumes memory ranges allocated and exported by the
 	  libnvdimm sub-system.
 
-	  Say Y if unsure
+	  Say M if unsure
+
+config DEV_DAX_KMEM
+	tristate "KMEM DAX: volatile-use of persistent memory"
+	default DEV_DAX
+	depends on DEV_DAX
+	depends on MEMORY_HOTPLUG # for add_memory() and friends
+	help
+	  Support access to persistent memory as if it were RAM.  This
+	  allows easier use of persistent memory by unmodified
+	  applications.
+
+	  To use this feature, a DAX device must be unbound from the
+	  device_dax driver (PMEM DAX) and bound to this kmem driver
+	  on each boot.
+
+	  Say N if unsure.
+
+config DEV_DAX_PMEM_COMPAT
+	tristate "PMEM DAX: support the deprecated /sys/class/dax interface"
+	depends on DEV_DAX_PMEM
+	default DEV_DAX_PMEM
+	help
+	  Older versions of the libdaxctl library expect to find all
+	  device-dax instances under /sys/class/dax. If libdaxctl in
+	  your distribution is older than v58 say M, otherwise say N.
 
 endif
diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
index 574286fac87c..81f7d54dadfb 100644
--- a/drivers/dax/Makefile
+++ b/drivers/dax/Makefile
@@ -1,8 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DAX) += dax.o
 obj-$(CONFIG_DEV_DAX) += device_dax.o
-obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
+obj-$(CONFIG_DEV_DAX_KMEM) += kmem.o
 
 dax-y := super.o
-dax_pmem-y := pmem.o
+dax-y += bus.o
 device_dax-y := device.o
+
+obj-y += pmem/
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
new file mode 100644
index 000000000000..2109cfe80219
--- /dev/null
+++ b/drivers/dax/bus.c
@@ -0,0 +1,503 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2017-2018 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
+#include <linux/device.h>
+#include <linux/mutex.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/dax.h>
+#include "dax-private.h"
+#include "bus.h"
+
+static struct class *dax_class;
+
+static DEFINE_MUTEX(dax_bus_lock);
+
+#define DAX_NAME_LEN 30
+struct dax_id {
+	struct list_head list;
+	char dev_name[DAX_NAME_LEN];
+};
+
+static int dax_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	/*
+	 * We only ever expect to handle device-dax instances, i.e. the
+	 * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
+	 */
+	return add_uevent_var(env, "MODALIAS=" DAX_DEVICE_MODALIAS_FMT, 0);
+}
+
+static struct dax_device_driver *to_dax_drv(struct device_driver *drv)
+{
+	return container_of(drv, struct dax_device_driver, drv);
+}
+
+static struct dax_id *__dax_match_id(struct dax_device_driver *dax_drv,
+		const char *dev_name)
+{
+	struct dax_id *dax_id;
+
+	lockdep_assert_held(&dax_bus_lock);
+
+	list_for_each_entry(dax_id, &dax_drv->ids, list)
+		if (sysfs_streq(dax_id->dev_name, dev_name))
+			return dax_id;
+	return NULL;
+}
+
+static int dax_match_id(struct dax_device_driver *dax_drv, struct device *dev)
+{
+	int match;
+
+	mutex_lock(&dax_bus_lock);
+	match = !!__dax_match_id(dax_drv, dev_name(dev));
+	mutex_unlock(&dax_bus_lock);
+
+	return match;
+}
+
+enum id_action {
+	ID_REMOVE,
+	ID_ADD,
+};
+
+static ssize_t do_id_store(struct device_driver *drv, const char *buf,
+		size_t count, enum id_action action)
+{
+	struct dax_device_driver *dax_drv = to_dax_drv(drv);
+	unsigned int region_id, id;
+	char devname[DAX_NAME_LEN];
+	struct dax_id *dax_id;
+	ssize_t rc = count;
+	int fields;
+
+	fields = sscanf(buf, "dax%d.%d", &region_id, &id);
+	if (fields != 2)
+		return -EINVAL;
+	sprintf(devname, "dax%d.%d", region_id, id);
+	if (!sysfs_streq(buf, devname))
+		return -EINVAL;
+
+	mutex_lock(&dax_bus_lock);
+	dax_id = __dax_match_id(dax_drv, buf);
+	if (!dax_id) {
+		if (action == ID_ADD) {
+			dax_id = kzalloc(sizeof(*dax_id), GFP_KERNEL);
+			if (dax_id) {
+				strncpy(dax_id->dev_name, buf, DAX_NAME_LEN);
+				list_add(&dax_id->list, &dax_drv->ids);
+			} else
+				rc = -ENOMEM;
+		} else
+			/* nothing to remove */;
+	} else if (action == ID_REMOVE) {
+		list_del(&dax_id->list);
+		kfree(dax_id);
+	} else
+		/* dax_id already added */;
+	mutex_unlock(&dax_bus_lock);
+
+	if (rc < 0)
+		return rc;
+	if (action == ID_ADD)
+		rc = driver_attach(drv);
+	if (rc)
+		return rc;
+	return count;
+}
+
+static ssize_t new_id_store(struct device_driver *drv, const char *buf,
+		size_t count)
+{
+	return do_id_store(drv, buf, count, ID_ADD);
+}
+static DRIVER_ATTR_WO(new_id);
+
+static ssize_t remove_id_store(struct device_driver *drv, const char *buf,
+		size_t count)
+{
+	return do_id_store(drv, buf, count, ID_REMOVE);
+}
+static DRIVER_ATTR_WO(remove_id);
+
+static struct attribute *dax_drv_attrs[] = {
+	&driver_attr_new_id.attr,
+	&driver_attr_remove_id.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(dax_drv);
+
+static int dax_bus_match(struct device *dev, struct device_driver *drv);
+
+static struct bus_type dax_bus_type = {
+	.name = "dax",
+	.uevent = dax_bus_uevent,
+	.match = dax_bus_match,
+	.drv_groups = dax_drv_groups,
+};
+
+static int dax_bus_match(struct device *dev, struct device_driver *drv)
+{
+	struct dax_device_driver *dax_drv = to_dax_drv(drv);
+
+	/*
+	 * All but the 'device-dax' driver, which has 'match_always'
+	 * set, requires an exact id match.
+	 */
+	if (dax_drv->match_always)
+		return 1;
+
+	return dax_match_id(dax_drv, dev);
+}
+
+/*
+ * Rely on the fact that drvdata is set before the attributes are
+ * registered, and that the attributes are unregistered before drvdata
+ * is cleared to assume that drvdata is always valid.
+ */
+static ssize_t id_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dax_region->id);
+}
+static DEVICE_ATTR_RO(id);
+
+static ssize_t region_size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%llu\n", (unsigned long long)
+			resource_size(&dax_region->res));
+}
+static struct device_attribute dev_attr_region_size = __ATTR(size, 0444,
+		region_size_show, NULL);
+
+static ssize_t align_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dax_region *dax_region = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", dax_region->align);
+}
+static DEVICE_ATTR_RO(align);
+
+static struct attribute *dax_region_attributes[] = {
+	&dev_attr_region_size.attr,
+	&dev_attr_align.attr,
+	&dev_attr_id.attr,
+	NULL,
+};
+
+static const struct attribute_group dax_region_attribute_group = {
+	.name = "dax_region",
+	.attrs = dax_region_attributes,
+};
+
+static const struct attribute_group *dax_region_attribute_groups[] = {
+	&dax_region_attribute_group,
+	NULL,
+};
+
+static void dax_region_free(struct kref *kref)
+{
+	struct dax_region *dax_region;
+
+	dax_region = container_of(kref, struct dax_region, kref);
+	kfree(dax_region);
+}
+
+void dax_region_put(struct dax_region *dax_region)
+{
+	kref_put(&dax_region->kref, dax_region_free);
+}
+EXPORT_SYMBOL_GPL(dax_region_put);
+
+static void dax_region_unregister(void *region)
+{
+	struct dax_region *dax_region = region;
+
+	sysfs_remove_groups(&dax_region->dev->kobj,
+			dax_region_attribute_groups);
+	dax_region_put(dax_region);
+}
+
+struct dax_region *alloc_dax_region(struct device *parent, int region_id,
+		struct resource *res, int target_node, unsigned int align,
+		unsigned long pfn_flags)
+{
+	struct dax_region *dax_region;
+
+	/*
+	 * The DAX core assumes that it can store its private data in
+	 * parent->driver_data. This WARN is a reminder / safeguard for
+	 * developers of device-dax drivers.
+	 */
+	if (dev_get_drvdata(parent)) {
+		dev_WARN(parent, "dax core failed to setup private data\n");
+		return NULL;
+	}
+
+	if (!IS_ALIGNED(res->start, align)
+			|| !IS_ALIGNED(resource_size(res), align))
+		return NULL;
+
+	dax_region = kzalloc(sizeof(*dax_region), GFP_KERNEL);
+	if (!dax_region)
+		return NULL;
+
+	dev_set_drvdata(parent, dax_region);
+	memcpy(&dax_region->res, res, sizeof(*res));
+	dax_region->pfn_flags = pfn_flags;
+	kref_init(&dax_region->kref);
+	dax_region->id = region_id;
+	dax_region->align = align;
+	dax_region->dev = parent;
+	dax_region->target_node = target_node;
+	if (sysfs_create_groups(&parent->kobj, dax_region_attribute_groups)) {
+		kfree(dax_region);
+		return NULL;
+	}
+
+	kref_get(&dax_region->kref);
+	if (devm_add_action_or_reset(parent, dax_region_unregister, dax_region))
+		return NULL;
+	return dax_region;
+}
+EXPORT_SYMBOL_GPL(alloc_dax_region);
+
+static ssize_t size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	unsigned long long size = resource_size(&dev_dax->region->res);
+
+	return sprintf(buf, "%llu\n", size);
+}
+static DEVICE_ATTR_RO(size);
+
+static int dev_dax_target_node(struct dev_dax *dev_dax)
+{
+	struct dax_region *dax_region = dev_dax->region;
+
+	return dax_region->target_node;
+}
+
+static ssize_t target_node_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	return sprintf(buf, "%d\n", dev_dax_target_node(dev_dax));
+}
+static DEVICE_ATTR_RO(target_node);
+
+static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
+		char *buf)
+{
+	/*
+	 * We only ever expect to handle device-dax instances, i.e. the
+	 * @type argument to MODULE_ALIAS_DAX_DEVICE() is always zero
+	 */
+	return sprintf(buf, DAX_DEVICE_MODALIAS_FMT "\n", 0);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static umode_t dev_dax_visible(struct kobject *kobj, struct attribute *a, int n)
+{
+	struct device *dev = container_of(kobj, struct device, kobj);
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	if (a == &dev_attr_target_node.attr && dev_dax_target_node(dev_dax) < 0)
+		return 0;
+	return a->mode;
+}
+
+static struct attribute *dev_dax_attributes[] = {
+	&dev_attr_modalias.attr,
+	&dev_attr_size.attr,
+	&dev_attr_target_node.attr,
+	NULL,
+};
+
+static const struct attribute_group dev_dax_attribute_group = {
+	.attrs = dev_dax_attributes,
+	.is_visible = dev_dax_visible,
+};
+
+static const struct attribute_group *dax_attribute_groups[] = {
+	&dev_dax_attribute_group,
+	NULL,
+};
+
+void kill_dev_dax(struct dev_dax *dev_dax)
+{
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+	struct inode *inode = dax_inode(dax_dev);
+
+	kill_dax(dax_dev);
+	unmap_mapping_range(inode->i_mapping, 0, 0, 1);
+}
+EXPORT_SYMBOL_GPL(kill_dev_dax);
+
+static void dev_dax_release(struct device *dev)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+	struct dax_region *dax_region = dev_dax->region;
+	struct dax_device *dax_dev = dev_dax->dax_dev;
+
+	dax_region_put(dax_region);
+	put_dax(dax_dev);
+	kfree(dev_dax);
+}
+
+static void unregister_dev_dax(void *dev)
+{
+	struct dev_dax *dev_dax = to_dev_dax(dev);
+
+	dev_dbg(dev, "%s\n", __func__);
+
+	kill_dev_dax(dev_dax);
+	device_del(dev);
+	put_device(dev);
+}
+
+struct dev_dax *__devm_create_dev_dax(struct dax_region *dax_region, int id,
+		struct dev_pagemap *pgmap, enum dev_dax_subsys subsys)
+{
+	struct device *parent = dax_region->dev;
+	struct dax_device *dax_dev;
+	struct dev_dax *dev_dax;
+	struct inode *inode;
+	struct device *dev;
+	int rc = -ENOMEM;
+
+	if (id < 0)
+		return ERR_PTR(-EINVAL);
+
+	dev_dax = kzalloc(sizeof(*dev_dax), GFP_KERNEL);
+	if (!dev_dax)
+		return ERR_PTR(-ENOMEM);
+
+	memcpy(&dev_dax->pgmap, pgmap, sizeof(*pgmap));
+
+	/*
+	 * No 'host' or dax_operations since there is no access to this
+	 * device outside of mmap of the resulting character device.
+	 */
+	dax_dev = alloc_dax(dev_dax, NULL, NULL);
+	if (!dax_dev)
+		goto err;
+
+	/* a device_dax instance is dead while the driver is not attached */
+	kill_dax(dax_dev);
+
+	/* from here on we're committed to teardown via dax_dev_release() */
+	dev = &dev_dax->dev;
+	device_initialize(dev);
+
+	dev_dax->dax_dev = dax_dev;
+	dev_dax->region = dax_region;
+	dev_dax->target_node = dax_region->target_node;
+	kref_get(&dax_region->kref);
+
+	inode = dax_inode(dax_dev);
+	dev->devt = inode->i_rdev;
+	if (subsys == DEV_DAX_BUS)
+		dev->bus = &dax_bus_type;
+	else
+		dev->class = dax_class;
+	dev->parent = parent;
+	dev->groups = dax_attribute_groups;
+	dev->release = dev_dax_release;
+	dev_set_name(dev, "dax%d.%d", dax_region->id, id);
+
+	rc = device_add(dev);
+	if (rc) {
+		kill_dev_dax(dev_dax);
+		put_device(dev);
+		return ERR_PTR(rc);
+	}
+
+	rc = devm_add_action_or_reset(dax_region->dev, unregister_dev_dax, dev);
+	if (rc)
+		return ERR_PTR(rc);
+
+	return dev_dax;
+
+ err:
+	kfree(dev_dax);
+
+	return ERR_PTR(rc);
+}
+EXPORT_SYMBOL_GPL(__devm_create_dev_dax);
+
+static int match_always_count;
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
+		struct module *module, const char *mod_name)
+{
+	struct device_driver *drv = &dax_drv->drv;
+	int rc = 0;
+
+	INIT_LIST_HEAD(&dax_drv->ids);
+	drv->owner = module;
+	drv->name = mod_name;
+	drv->mod_name = mod_name;
+	drv->bus = &dax_bus_type;
+
+	/* there can only be one default driver */
+	mutex_lock(&dax_bus_lock);
+	match_always_count += dax_drv->match_always;
+	if (match_always_count > 1) {
+		match_always_count--;
+		WARN_ON(1);
+		rc = -EINVAL;
+	}
+	mutex_unlock(&dax_bus_lock);
+	if (rc)
+		return rc;
+	return driver_register(drv);
+}
+EXPORT_SYMBOL_GPL(__dax_driver_register);
+
+void dax_driver_unregister(struct dax_device_driver *dax_drv)
+{
+	struct device_driver *drv = &dax_drv->drv;
+	struct dax_id *dax_id, *_id;
+
+	mutex_lock(&dax_bus_lock);
+	match_always_count -= dax_drv->match_always;
+	list_for_each_entry_safe(dax_id, _id, &dax_drv->ids, list) {
+		list_del(&dax_id->list);
+		kfree(dax_id);
+	}
+	mutex_unlock(&dax_bus_lock);
+	driver_unregister(drv);
+}
+EXPORT_SYMBOL_GPL(dax_driver_unregister);
+
+int __init dax_bus_init(void)
+{
+	int rc;
+
+	if (IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)) {
+		dax_class = class_create(THIS_MODULE, "dax");
+		if (IS_ERR(dax_class))
+			return PTR_ERR(dax_class);
+	}
+
+	rc = bus_register(&dax_bus_type);
+	if (rc)
+		class_destroy(dax_class);
+	return rc;
+}
+
+void __exit dax_bus_exit(void)
+{
+	bus_unregister(&dax_bus_type);
+	class_destroy(dax_class);
+}
diff --git a/drivers/dax/bus.h b/drivers/dax/bus.h
new file mode 100644
index 000000000000..8619e3299943
--- /dev/null
+++ b/drivers/dax/bus.h
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016 - 2018 Intel Corporation. All rights reserved. */
+#ifndef __DAX_BUS_H__
+#define __DAX_BUS_H__
+#include <linux/device.h>
+
+struct dev_dax;
+struct resource;
+struct dax_device;
+struct dax_region;
+void dax_region_put(struct dax_region *dax_region);
+struct dax_region *alloc_dax_region(struct device *parent, int region_id,
+		struct resource *res, int target_node, unsigned int align,
+		unsigned long flags);
+
+enum dev_dax_subsys {
+	DEV_DAX_BUS,
+	DEV_DAX_CLASS,
+};
+
+struct dev_dax *__devm_create_dev_dax(struct dax_region *dax_region, int id,
+		struct dev_pagemap *pgmap, enum dev_dax_subsys subsys);
+
+static inline struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
+		int id, struct dev_pagemap *pgmap)
+{
+	return __devm_create_dev_dax(dax_region, id, pgmap, DEV_DAX_BUS);
+}
+
+/* to be deleted when DEV_DAX_CLASS is removed */
+struct dev_dax *__dax_pmem_probe(struct device *dev, enum dev_dax_subsys subsys);
+
+struct dax_device_driver {
+	struct device_driver drv;
+	struct list_head ids;
+	int match_always;
+};
+
+int __dax_driver_register(struct dax_device_driver *dax_drv,
+		struct module *module, const char *mod_name);
+#define dax_driver_register(driver) \
+	__dax_driver_register(driver, THIS_MODULE, KBUILD_MODNAME)
+void dax_driver_unregister(struct dax_device_driver *dax_drv);
+void kill_dev_dax(struct dev_dax *dev_dax);
+
+#if IS_ENABLED(CONFIG_DEV_DAX_PMEM_COMPAT)
+int dev_dax_probe(struct device *dev);
+#endif
+
+/*
+ * While run_dax() is potentially a generic operation that could be
+ * defined in include/linux/dax.h we don't want to grow any users
+ * outside of drivers/dax/
+ */
+void run_dax(struct dax_device *dax_dev);
+
+#define MODULE_ALIAS_DAX_DEVICE(type) \
+	MODULE_ALIAS("dax:t" __stringify(type) "*")
+#define DAX_DEVICE_MODALIAS_FMT "dax:t%d"
+
+#endif /* __DAX_BUS_H__ */
diff --git a/drivers/dax/dax-private.h b/drivers/dax/dax-private.h
index b6fc4f04636d..a45612148ca0 100644
--- a/drivers/dax/dax-private.h
+++ b/drivers/dax/dax-private.h
@@ -16,10 +16,17 @@
 #include <linux/device.h>
 #include <linux/cdev.h>
 
+/* private routines between core files */
+struct dax_device;
+struct dax_device *inode_dax(struct inode *inode);
+struct inode *dax_inode(struct dax_device *dax_dev);
+int dax_bus_init(void);
+void dax_bus_exit(void);
+
 /**
  * struct dax_region - mapping infrastructure for dax devices
  * @id: kernel-wide unique region for a memory range
- * @base: linear address corresponding to @res
+ * @target_node: effective numa node if this memory range is onlined
  * @kref: to pin while other agents have a need to do lookups
  * @dev: parent device backing this region
  * @align: allocation and mapping alignment for child dax devices
@@ -28,8 +35,7 @@
  */
 struct dax_region {
 	int id;
-	struct ida ida;
-	void *base;
+	int target_node;
 	struct kref kref;
 	struct device *dev;
 	unsigned int align;
@@ -38,20 +44,28 @@ struct dax_region {
 };
 
 /**
- * struct dev_dax - instance data for a subdivision of a dax region
+ * struct dev_dax - instance data for a subdivision of a dax region, and
+ * data while the device is activated in the driver.
  * @region - parent region
  * @dax_dev - core dax functionality
+ * @target_node: effective numa node if dev_dax memory range is onlined
  * @dev - device core
- * @id - child id in the region
- * @num_resources - number of physical address extents in this device
- * @res - array of physical address ranges
+ * @pgmap - pgmap for memmap setup / lifetime (driver owned)
+ * @ref: pgmap reference count (driver owned)
+ * @cmp: @ref final put completion (driver owned)
  */
 struct dev_dax {
 	struct dax_region *region;
 	struct dax_device *dax_dev;
+	int target_node;
 	struct device dev;
-	int id;
-	int num_resources;
-	struct resource res[0];
+	struct dev_pagemap pgmap;
+	struct percpu_ref ref;
+	struct completion cmp;
 };
+
+static inline struct dev_dax *to_dev_dax(struct device *dev)
+{
+	return container_of(dev, struct dev_dax, dev);
+}
 #endif
diff --git a/drivers/dax/dax.h b/drivers/dax/dax.h
deleted file mode 100644
index f9e5feea742c..000000000000
--- a/drivers/dax/dax.h
+++ /dev/null
@@ -1,18 +0,0 @@
-/*
- * Copyright(c) 2016 - 2017 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 __DAX_H__
-#define __DAX_H__
-struct dax_device;
-struct dax_device *inode_dax(struct inode *inode);
-struct inode *dax_inode(struct dax_device *dax_dev);
-#endif /* __DAX_H__ */
diff --git a/drivers/dax/device-dax.h b/drivers/dax/device-dax.h
deleted file mode 100644
index 688b051750bd..000000000000
--- a/drivers/dax/device-dax.h
+++ /dev/null
@@ -1,25 +0,0 @@
-/*
- * Copyright(c) 2016 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 __DEVICE_DAX_H__
-#define __DEVICE_DAX_H__
-struct device;
-struct dev_dax;
-struct resource;
-struct dax_region;
-void dax_region_put(struct dax_region *dax_region);
-struct dax_region *alloc_dax_region(struct device *parent,
-		int region_id, struct resource *res, unsigned int align,
-		void *addr, unsigned long flags);
-struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
-		int id, struct resource *res, int count);
-#endif /* __DEVICE_DAX_H__ */
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 948806e57cee..e428468ab661 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -1,15 +1,6 @@
-/*
- * Copyright(c) 2016 - 2017 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.
- */
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright(c) 2016-2018 Intel Corporation. All rights reserved. */
+#include <linux/memremap.h>
 #include <linux/pagemap.h>
 #include <linux/module.h>
 #include <linux/device.h>
@@ -21,161 +12,39 @@
 #include <linux/mm.h>
 #include <linux/mman.h>
 #include "dax-private.h"
-#include "dax.h"
+#include "bus.h"
 
-static struct class *dax_class;
-
-/*
- * Rely on the fact that drvdata is set before the attributes are
- * registered, and that the attributes are unregistered before drvdata
- * is cleared to assume that drvdata is always valid.
- */
-static ssize_t id_show(struct device *dev,
-		struct device_attribute *attr, char *buf)
-{
-	struct dax_region *dax_region = dev_get_drvdata(dev);
-
-	return sprintf(buf, "%d\n", dax_region->id);
-}
-static DEVICE_ATTR_RO(id);
-
-static ssize_t region_size_show(struct device *dev,
-		s