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Subject[PATCH v5 5/6] x86/NUMA: Provide a range-to-target_node lookup facility
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The DEV_DAX_KMEM facility is a generic mechanism to allow device-dax
instances, fronting performance-differentiated-memory like pmem, to be
added to the System RAM pool. The NUMA node for that hot-added memory is
derived from the device-dax instance's 'target_node' attribute.

Recall that the 'target_node' is the ACPI-PXM-to-node translation for
memory when it comes online whereas the 'numa_node' attribute of the
device represents the closest online cpu node.

Presently useful target_node information from the ACPI SRAT is discarded
with the expectation that "Reserved" memory will never be onlined. Now,
DEV_DAX_KMEM violates that assumption, there is a need to retain the
translation. Move, rather than discard, numa_memblk data to a secondary
array that memory_add_physaddr_to_target_node() may consider at a later
point in time.

Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
arch/x86/mm/numa.c | 61 ++++++++++++++++++++++++++++++++++++++++++--------
include/linux/numa.h | 14 +++++++++++
2 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 2450b21cc28a..59ba008504dc 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -26,6 +26,7 @@ struct pglist_data *node_data[MAX_NUMNODES] __read_mostly;
EXPORT_SYMBOL(node_data);

static struct numa_meminfo numa_meminfo __initdata_or_meminfo;
+static struct numa_meminfo numa_reserved_meminfo __initdata_or_meminfo;

static int numa_distance_cnt;
static u8 *numa_distance;
@@ -164,6 +165,19 @@ void __init numa_remove_memblk_from(int idx, struct numa_meminfo *mi)
(mi->nr_blks - idx) * sizeof(mi->blk[0]));
}

+/**
+ * numa_move_tail_memblk - Move a numa_memblk from one numa_meminfo to another
+ * @dst: numa_meminfo to append block to
+ * @idx: Index of memblk to remove
+ * @src: numa_meminfo to remove memblk from
+ */
+static void __init numa_move_tail_memblk(struct numa_meminfo *dst, int idx,
+ struct numa_meminfo *src)
+{
+ dst->blk[dst->nr_blks++] = src->blk[idx];
+ numa_remove_memblk_from(idx, src);
+}
+
/**
* numa_add_memblk - Add one numa_memblk to numa_meminfo
* @nid: NUMA node ID of the new memblk
@@ -233,14 +247,19 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
for (i = 0; i < mi->nr_blks; i++) {
struct numa_memblk *bi = &mi->blk[i];

- /* make sure all blocks are inside the limits */
+ /* move / save reserved memory ranges */
+ if (!memblock_overlaps_region(&memblock.memory,
+ bi->start, bi->end - bi->start)) {
+ numa_move_tail_memblk(&numa_reserved_meminfo, i--, mi);
+ continue;
+ }
+
+ /* make sure all non-reserved blocks are inside the limits */
bi->start = max(bi->start, low);
bi->end = min(bi->end, high);

- /* and there's no empty or non-exist block */
- if (bi->start >= bi->end ||
- !memblock_overlaps_region(&memblock.memory,
- bi->start, bi->end - bi->start))
+ /* and there's no empty block */
+ if (bi->start >= bi->end)
numa_remove_memblk_from(i--, mi);
}

@@ -877,16 +896,38 @@ EXPORT_SYMBOL(cpumask_of_node);

#endif /* !CONFIG_DEBUG_PER_CPU_MAPS */

-#ifdef CONFIG_MEMORY_HOTPLUG
-int memory_add_physaddr_to_nid(u64 start)
+#ifdef CONFIG_NUMA_KEEP_MEMINFO
+static int meminfo_to_nid(struct numa_meminfo *mi, u64 start)
{
- struct numa_meminfo *mi = &numa_meminfo;
- int nid = mi->blk[0].nid;
int i;

for (i = 0; i < mi->nr_blks; i++)
if (mi->blk[i].start <= start && mi->blk[i].end > start)
- nid = mi->blk[i].nid;
+ return mi->blk[i].nid;
+ return NUMA_NO_NODE;
+}
+
+int phys_to_target_node(phys_addr_t start)
+{
+ int nid = meminfo_to_nid(&numa_meminfo, start);
+
+ /*
+ * Prefer online nodes, but if reserved memory might be
+ * hot-added continue the search with reserved ranges.
+ */
+ if (nid != NUMA_NO_NODE)
+ return nid;
+
+ return meminfo_to_nid(&numa_reserved_meminfo, start);
+}
+EXPORT_SYMBOL_GPL(phys_to_target_node);
+
+int memory_add_physaddr_to_nid(u64 start)
+{
+ int nid = meminfo_to_nid(&numa_meminfo, start);
+
+ if (nid == NUMA_NO_NODE)
+ nid = numa_meminfo.blk[0].nid;
return nid;
}
EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
diff --git a/include/linux/numa.h b/include/linux/numa.h
index 5773cd2613fc..a42df804679e 100644
--- a/include/linux/numa.h
+++ b/include/linux/numa.h
@@ -1,7 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_NUMA_H
#define _LINUX_NUMA_H
-
+#include <linux/types.h>

#ifdef CONFIG_NODES_SHIFT
#define NODES_SHIFT CONFIG_NODES_SHIFT
@@ -21,12 +21,24 @@
#endif

#ifdef CONFIG_NUMA
+/* Generic implementation available */
int numa_map_to_online_node(int node);
+
+/*
+ * Optional architecture specific implementation, users need a "depends
+ * on $ARCH"
+ */
+int phys_to_target_node(phys_addr_t addr);
#else
static inline int numa_map_to_online_node(int node)
{
return NUMA_NO_NODE;
}
+
+static inline int phys_to_target_node(phys_addr_t addr)
+{
+ return NUMA_NO_NODE;
+}
#endif

#endif /* _LINUX_NUMA_H */
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