acpi/nfit, device-dax: Identify differentiated memory with a unique numa-node

Persistent memory, as described by the ACPI NFIT (NVDIMM Firmware
Interface Table), is the first known instance of a memory range
described by a unique "target" proximity domain. Where "initiator" and
"target" proximity domains is an approach that the ACPI HMAT
(Heterogeneous Memory Attributes Table) uses to described the unique
performance properties of a memory range relative to a given initiator
(e.g. CPU or DMA device).

Currently the numa-node for a /dev/pmemX block-device or /dev/daxX.Y
char-device follows the traditional notion of 'numa-node' where the
attribute conveys the closest online numa-node. That numa-node attribute
is useful for cpu-binding and memory-binding processes *near* the
device. However, when the memory range backing a 'pmem', or 'dax' device
is onlined (memory hot-add) the memory-only-numa-node representing that
address needs to be differentiated from the set of online nodes. In
other words, the numa-node association of the device depends on whether
you can bind processes *near* the cpu-numa-node in the offline
device-case, or bind process *on* the memory-range directly after the
backing address range is onlined.

Allow for the case that platform firmware describes persistent memory
with a unique proximity domain, i.e. when it is distinct from the
proximity of DRAM and CPUs that are on the same socket. Plumb the Linux
numa-node translation of that proximity through the libnvdimm region
device to namespaces that are in device-dax mode. With this in place the
proposed kmem driver [1] can optionally discover a unique numa-node
number for the address range as it transitions the memory from an
offline state managed by a device-driver to an online memory range
managed by the core-mm.

[1]: https://lore.kernel.org/lkml/[e-mail]

Reported-by: Fan Du <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: "Oliver O'Halloran" <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Jérôme Glisse <[e-mail]>
Reviewed-by: Yang Shi <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>

arch/powerpc/platforms/pseries/papr_scm.c

···
 	memset(&ndr_desc, 0, sizeof(ndr_desc));
 	ndr_desc.attr_groups = region_attr_groups;
 	ndr_desc.numa_node = dev_to_node(&p->pdev->dev);
+	ndr_desc.target_node = ndr_desc.numa_node;
 	ndr_desc.res = &p->res;
 	ndr_desc.of_node = p->dn;
 	ndr_desc.provider_data = p;

drivers/acpi/nfit/core.c

···
 	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

drivers/acpi/numa.c

···
 
 	return node;
 }
+EXPORT_SYMBOL(acpi_map_pxm_to_node);
 
 /**
  * acpi_map_pxm_to_online_node - Map proximity ID to online node

drivers/dax/bus.c

···
 }
 
 struct dax_region *alloc_dax_region(struct device *parent, int region_id,
-		struct resource *res, unsigned int align,
+		struct resource *res, int target_node, unsigned int align,
 		unsigned long pfn_flags)
 {
 	struct dax_region *dax_region;
···
 	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;
···
 
 	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);

drivers/dax/bus.h

···
 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, unsigned long flags);
+		struct resource *res, int target_node, unsigned int align,
+		unsigned long flags);
 
 enum dev_dax_subsys {
 	DEV_DAX_BUS,

drivers/dax/dax-private.h

···
 /**
  * struct dax_region - mapping infrastructure for dax devices
  * @id: kernel-wide unique region for a memory range
+ * @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
···
  */
 struct dax_region {
 	int id;
+	int target_node;
 	struct kref kref;
 	struct device *dev;
 	unsigned int align;
···
  * 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
  * @pgmap - pgmap for memmap setup / lifetime (driver owned)
  * @ref: pgmap reference count (driver owned)
···
 struct dev_dax {
 	struct dax_region *region;
 	struct dax_device *dax_dev;
+	int target_node;
 	struct device dev;
 	struct dev_pagemap pgmap;
 	struct percpu_ref ref;

drivers/dax/pmem/core.c

···
 	struct nd_namespace_common *ndns;
 	struct nd_dax *nd_dax = to_nd_dax(dev);
 	struct nd_pfn *nd_pfn = &nd_dax->nd_pfn;
+	struct nd_region *nd_region = to_nd_region(dev->parent);
 
 	ndns = nvdimm_namespace_common_probe(dev);
 	if (IS_ERR(ndns))
···
 	memcpy(&res, &pgmap.res, sizeof(res));
 	res.start += offset;
 	dax_region = alloc_dax_region(dev, region_id, &res,
-			le32_to_cpu(pfn_sb->align), PFN_DEV|PFN_MAP);
+			nd_region->target_node, le32_to_cpu(pfn_sb->align),
+			PFN_DEV|PFN_MAP);
 	if (!dax_region)
 		return ERR_PTR(-ENOMEM);
 

drivers/nvdimm/e820.c

···
 	ndr_desc.res = res;
 	ndr_desc.attr_groups = e820_pmem_region_attribute_groups;
 	ndr_desc.numa_node = e820_range_to_nid(res->start);
+	ndr_desc.target_node = ndr_desc.numa_node;
 	set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
 	if (!nvdimm_pmem_region_create(nvdimm_bus, &ndr_desc))
 		return -ENXIO;

drivers/nvdimm/nd.h

···
 	u16 ndr_mappings;
 	u64 ndr_size;
 	u64 ndr_start;
-	int id, num_lanes, ro, numa_node;
+	int id, num_lanes, ro, numa_node, target_node;
 	void *provider_data;
 	struct kernfs_node *bb_state;
 	struct badblocks bb;

drivers/nvdimm/of_pmem.c

···
 		memset(&ndr_desc, 0, sizeof(ndr_desc));
 		ndr_desc.attr_groups = region_attr_groups;
 		ndr_desc.numa_node = dev_to_node(&pdev->dev);
+		ndr_desc.target_node = ndr_desc.numa_node;
 		ndr_desc.res = &pdev->resource[i];
 		ndr_desc.of_node = np;
 		set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);

drivers/nvdimm/region_devs.c

···
 	nd_region->flags = ndr_desc->flags;
 	nd_region->ro = ro;
 	nd_region->numa_node = ndr_desc->numa_node;
+	nd_region->target_node = ndr_desc->target_node;
 	ida_init(&nd_region->ns_ida);
 	ida_init(&nd_region->btt_ida);
 	ida_init(&nd_region->pfn_ida);

include/linux/acpi.h

···
 
 #ifdef CONFIG_ACPI_NUMA
 int acpi_map_pxm_to_online_node(int pxm);
+int acpi_map_pxm_to_node(int pxm);
 int acpi_get_node(acpi_handle handle);
 #else
 static inline int acpi_map_pxm_to_online_node(int pxm)
+{
+	return 0;
+}
+static inline int acpi_map_pxm_to_node(int pxm)
 {
 	return 0;
 }

include/linux/libnvdimm.h

···
 	void *provider_data;
 	int num_lanes;
 	int numa_node;
+	int target_node;
 	unsigned long flags;
 	struct device_node *of_node;
 };