[PATCH v2] mm: numa_memblks: introduce numa_add_reserved_memblk

Yuquan Wang
2025-04-09T04:02:37Z

acpi_parse_cfmws() currently adds empty CFMWS ranges to numa_meminfo
with the expectation that numa_cleanup_meminfo moves them to
numa_reserved_meminfo. There is no need for that indirection when it is
known in advance that these unpopulated ranges are meant for
numa_reserved_meminfo in support of future hotplug / CXL provisioning.

Introduce and use numa_add_reserved_memblk() to add the empty CFMWS
ranges directly.

Signed-off-by: Yuquan Wang <wangyuquan1236@phytium.com.cn>
---

Changes in v2 (Thanks to Dan & Alison):
- Use numa_add_reserved_memblk() to replace numa_add_memblk() in acpi_parse_cfmws()
- Add comments to describe the usage of numa_add_reserved_memblk()
- Updating the commit message to clarify the purpose of the patch

drivers/acpi/numa/srat.c | 2 +-
include/linux/numa_memblks.h | 1 +
mm/numa_memblks.c | 22 ++++++++++++++++++++++
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/numa/srat.c b/drivers/acpi/numa/srat.c
index 0a725e46d017..751774f0b4e5 100644
--- a/drivers/acpi/numa/srat.c
+++ b/drivers/acpi/numa/srat.c
@@ -453,7 +453,7 @@ static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
return -EINVAL;
}

- if (numa_add_memblk(node, start, end) < 0) {
+ if (numa_add_reserved_memblk(node, start, end) < 0) {
/* CXL driver must handle the NUMA_NO_NODE case */
pr_warn("ACPI NUMA: Failed to add memblk for CFMWS node %d [mem %#llx-%#llx]\n",
node, start, end);
diff --git a/include/linux/numa_memblks.h b/include/linux/numa_memblks.h
index dd85613cdd86..991076cba7c5 100644
--- a/include/linux/numa_memblks.h
+++ b/include/linux/numa_memblks.h
@@ -22,6 +22,7 @@ struct numa_meminfo {
};

int __init numa_add_memblk(int nodeid, u64 start, u64 end);
+int __init numa_add_reserved_memblk(int nid, u64 start, u64 end);
void __init numa_remove_memblk_from(int idx, struct numa_meminfo *mi);

int __init numa_cleanup_meminfo(struct numa_meminfo *mi);
diff --git a/mm/numa_memblks.c b/mm/numa_memblks.c
index ff4054f4334d..541a99c4071a 100644
--- a/mm/numa_memblks.c
+++ b/mm/numa_memblks.c
@@ -200,6 +200,28 @@ int __init numa_add_memblk(int nid, u64 start, u64 end)
return numa_add_memblk_to(nid, start, end, &numa_meminfo);
}

+/**
+ * numa_add_reserved_memblk - Add one numa_memblk to numa_reserved_meminfo
+ * @nid: NUMA node ID of the new memblk
+ * @start: Start address of the new memblk
+ * @end: End address of the new memblk
+ *
+ * Add a new memblk to the numa_reserved_meminfo.
+ *
+ * Usage Case: numa_cleanup_meminfo() reconciles all numa_memblk instances
+ * against memblock_type information and moves any that intersect reserved
+ * ranges to numa_reserved_meminfo. However, when that information is known
+ * ahead of time, we use numa_add_reserved_memblk() to add the numa_memblk
+ * to numa_reserved_meminfo directly.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int __init numa_add_reserved_memblk(int nid, u64 start, u64 end)
+{
+ return numa_add_memblk_to(nid, start, end, &numa_reserved_meminfo);
+}
+
/**
* numa_cleanup_meminfo - Cleanup a numa_meminfo
* @mi: numa_meminfo to clean up
--
2.34.1