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/20181022201317.8558C1D8@viggo.jf.intel.com

Reported-by: Fan Du <fan.du@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Oliver O'Halloran" <oohall@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

4 files changed, 4 insertions, 1 deletions

diff --git a/drivers/nvdimm/e820.c b/drivers/nvdimm/e820.c
index 521eaf53a52a..36be9b619187 100644
--- a/drivers/nvdimm/e820.c
+++ b/drivers/nvdimm/e820.c
@@ -47,6 +47,7 @@ static int e820_register_one(struct resource *res, void *data)
 	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;
diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index cfde992684e7..0b3d7595b3cb 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -153,7 +153,7 @@ struct nd_region {
 	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;
diff --git a/drivers/nvdimm/of_pmem.c b/drivers/nvdimm/of_pmem.c
index 0a701837dfc0..ecaaa27438e2 100644
--- a/drivers/nvdimm/of_pmem.c
+++ b/drivers/nvdimm/of_pmem.c
@@ -68,6 +68,7 @@ static int of_pmem_region_probe(struct platform_device *pdev)
 		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);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index e2818f94f292..caf2f3129ccd 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1065,6 +1065,7 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	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);