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From:   Rongwei Wang <rongwei.wang@linux.alibaba.com>
To:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Cc:     akpm@linux-foundation.org, willy@infradead.org,
        catalin.marinas@arm.com, dave.hansen@linux.intel.com,
        tj@kernel.org, mingo@redhat.com
Subject: [PATCH RFC 1/5] mm/numa: move numa emulation APIs into generic files
Date:   Thu, 12 Oct 2023 10:48:38 +0800
Message-Id: <20231012024842.99703-2-rongwei.wang@linux.alibaba.com>
In-Reply-To: <20231012024842.99703-1-rongwei.wang@linux.alibaba.com>
References: <20231012024842.99703-1-rongwei.wang@linux.alibaba.com>
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Precedence: bulk

In order to support NUMA EMU for other
arch, some functions that used by numa_meminfo
should be moved out x86 arch. mm/numa.c created
to place above API.

CONFIG_NUMA_EMU will be handled later.

Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com>
---
 arch/x86/include/asm/numa.h |   3 -
 arch/x86/mm/numa.c          | 216 +-------------------------
 arch/x86/mm/numa_internal.h |  14 +-
 include/asm-generic/numa.h  |  18 +++
 mm/Makefile                 |   1 +
 mm/numa.c                   | 298 ++++++++++++++++++++++++++++++++++++
 6 files changed, 323 insertions(+), 227 deletions(-)
 create mode 100644 mm/numa.c

diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h
index e3bae2b60a0d..8d79be8095d5 100644
--- a/arch/x86/include/asm/numa.h
+++ b/arch/x86/include/asm/numa.h
@@ -9,9 +9,6 @@
 #include <asm/apicdef.h>
 
 #ifdef CONFIG_NUMA
-
-#define NR_NODE_MEMBLKS		(MAX_NUMNODES*2)
-
 /*
  * Too small node sizes may confuse the VM badly. Usually they
  * result from BIOS bugs. So dont recognize nodes as standalone
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 2aadb2019b4f..969b11fff03f 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -25,8 +25,8 @@ nodemask_t numa_nodes_parsed __initdata;
 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;
+extern struct numa_meminfo numa_meminfo;
+extern struct numa_meminfo numa_reserved_meminfo;
 
 static int numa_distance_cnt;
 static u8 *numa_distance;
@@ -148,34 +148,6 @@ static int __init numa_add_memblk_to(int nid, u64 start, u64 end,
 	return 0;
 }
 
-/**
- * numa_remove_memblk_from - Remove one numa_memblk from a numa_meminfo
- * @idx: Index of memblk to remove
- * @mi: numa_meminfo to remove memblk from
- *
- * Remove @idx'th numa_memblk from @mi by shifting @mi->blk[] and
- * decrementing @mi->nr_blks.
- */
-void __init numa_remove_memblk_from(int idx, struct numa_meminfo *mi)
-{
-	mi->nr_blks--;
-	memmove(&mi->blk[idx], &mi->blk[idx + 1],
-		(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
@@ -225,124 +197,6 @@ static void __init alloc_node_data(int nid)
 	node_set_online(nid);
 }
 
-/**
- * numa_cleanup_meminfo - Cleanup a numa_meminfo
- * @mi: numa_meminfo to clean up
- *
- * Sanitize @mi by merging and removing unnecessary memblks.  Also check for
- * conflicts and clear unused memblks.
- *
- * RETURNS:
- * 0 on success, -errno on failure.
- */
-int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
-{
-	const u64 low = 0;
-	const u64 high = PFN_PHYS(max_pfn);
-	int i, j, k;
-
-	/* first, trim all entries */
-	for (i = 0; i < mi->nr_blks; i++) {
-		struct numa_memblk *bi = &mi->blk[i];
-
-		/* 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);
-
-		/* preserve info for non-RAM areas above 'max_pfn': */
-		if (bi->end > high) {
-			numa_add_memblk_to(bi->nid, high, bi->end,
-					   &numa_reserved_meminfo);
-			bi->end = high;
-		}
-
-		/* and there's no empty block */
-		if (bi->start >= bi->end)
-			numa_remove_memblk_from(i--, mi);
-	}
-
-	/* merge neighboring / overlapping entries */
-	for (i = 0; i < mi->nr_blks; i++) {
-		struct numa_memblk *bi = &mi->blk[i];
-
-		for (j = i + 1; j < mi->nr_blks; j++) {
-			struct numa_memblk *bj = &mi->blk[j];
-			u64 start, end;
-
-			/*
-			 * See whether there are overlapping blocks.  Whine
-			 * about but allow overlaps of the same nid.  They
-			 * will be merged below.
-			 */
-			if (bi->end > bj->start && bi->start < bj->end) {
-				if (bi->nid != bj->nid) {
-					pr_err("node %d [mem %#010Lx-%#010Lx] overlaps with node %d [mem %#010Lx-%#010Lx]\n",
-					       bi->nid, bi->start, bi->end - 1,
-					       bj->nid, bj->start, bj->end - 1);
-					return -EINVAL;
-				}
-				pr_warn("Warning: node %d [mem %#010Lx-%#010Lx] overlaps with itself [mem %#010Lx-%#010Lx]\n",
-					bi->nid, bi->start, bi->end - 1,
-					bj->start, bj->end - 1);
-			}
-
-			/*
-			 * Join together blocks on the same node, holes
-			 * between which don't overlap with memory on other
-			 * nodes.
-			 */
-			if (bi->nid != bj->nid)
-				continue;
-			start = min(bi->start, bj->start);
-			end = max(bi->end, bj->end);
-			for (k = 0; k < mi->nr_blks; k++) {
-				struct numa_memblk *bk = &mi->blk[k];
-
-				if (bi->nid == bk->nid)
-					continue;
-				if (start < bk->end && end > bk->start)
-					break;
-			}
-			if (k < mi->nr_blks)
-				continue;
-			printk(KERN_INFO "NUMA: Node %d [mem %#010Lx-%#010Lx] + [mem %#010Lx-%#010Lx] -> [mem %#010Lx-%#010Lx]\n",
-			       bi->nid, bi->start, bi->end - 1, bj->start,
-			       bj->end - 1, start, end - 1);
-			bi->start = start;
-			bi->end = end;
-			numa_remove_memblk_from(j--, mi);
-		}
-	}
-
-	/* clear unused ones */
-	for (i = mi->nr_blks; i < ARRAY_SIZE(mi->blk); i++) {
-		mi->blk[i].start = mi->blk[i].end = 0;
-		mi->blk[i].nid = NUMA_NO_NODE;
-	}
-
-	return 0;
-}
-
-/*
- * Set nodes, which have memory in @mi, in *@nodemask.
- */
-static void __init numa_nodemask_from_meminfo(nodemask_t *nodemask,
-					      const struct numa_meminfo *mi)
-{
-	int i;
-
-	for (i = 0; i < ARRAY_SIZE(mi->blk); i++)
-		if (mi->blk[i].start != mi->blk[i].end &&
-		    mi->blk[i].nid != NUMA_NO_NODE)
-			node_set(mi->blk[i].nid, *nodemask);
-}
-
 /**
  * numa_reset_distance - Reset NUMA distance table
  *
@@ -478,72 +332,6 @@ static bool __init numa_meminfo_cover_memory(const struct numa_meminfo *mi)
 	return true;
 }
 
-/*
- * Mark all currently memblock-reserved physical memory (which covers the
- * kernel's own memory ranges) as hot-unswappable.
- */
-static void __init numa_clear_kernel_node_hotplug(void)
-{
-	nodemask_t reserved_nodemask = NODE_MASK_NONE;
-	struct memblock_region *mb_region;
-	int i;
-
-	/*
-	 * We have to do some preprocessing of memblock regions, to
-	 * make them suitable for reservation.
-	 *
-	 * At this time, all memory regions reserved by memblock are
-	 * used by the kernel, but those regions are not split up
-	 * along node boundaries yet, and don't necessarily have their
-	 * node ID set yet either.
-	 *
-	 * So iterate over all memory known to the x86 architecture,
-	 * and use those ranges to set the nid in memblock.reserved.
-	 * This will split up the memblock regions along node
-	 * boundaries and will set the node IDs as well.
-	 */
-	for (i = 0; i < numa_meminfo.nr_blks; i++) {
-		struct numa_memblk *mb = numa_meminfo.blk + i;
-		int ret;
-
-		ret = memblock_set_node(mb->start, mb->end - mb->start, &memblock.reserved, mb->nid);
-		WARN_ON_ONCE(ret);
-	}
-
-	/*
-	 * Now go over all reserved memblock regions, to construct a
-	 * node mask of all kernel reserved memory areas.
-	 *
-	 * [ Note, when booting with mem=nn[kMG] or in a kdump kernel,
-	 *   numa_meminfo might not include all memblock.reserved
-	 *   memory ranges, because quirks such as trim_snb_memory()
-	 *   reserve specific pages for Sandy Bridge graphics. ]
-	 */
-	for_each_reserved_mem_region(mb_region) {
-		int nid = memblock_get_region_node(mb_region);
-
-		if (nid != MAX_NUMNODES)
-			node_set(nid, reserved_nodemask);
-	}
-
-	/*
-	 * Finally, clear the MEMBLOCK_HOTPLUG flag for all memory
-	 * belonging to the reserved node mask.
-	 *
-	 * Note that this will include memory regions that reside
-	 * on nodes that contain kernel memory - entire nodes
-	 * become hot-unpluggable:
-	 */
-	for (i = 0; i < numa_meminfo.nr_blks; i++) {
-		struct numa_memblk *mb = numa_meminfo.blk + i;
-
-		if (!node_isset(mb->nid, reserved_nodemask))
-			continue;
-
-		memblock_clear_hotplug(mb->start, mb->end - mb->start);
-	}
-}
-
 static int __init numa_register_memblks(struct numa_meminfo *mi)
 {
 	int i, nid;
diff --git a/arch/x86/mm/numa_internal.h b/arch/x86/mm/numa_internal.h
index 86860f279662..b6053beb81b1 100644
--- a/arch/x86/mm/numa_internal.h
+++ b/arch/x86/mm/numa_internal.h
@@ -16,19 +16,13 @@ struct numa_meminfo {
 	struct numa_memblk	blk[NR_NODE_MEMBLKS];
 };
 
-void __init numa_remove_memblk_from(int idx, struct numa_meminfo *mi);
-int __init numa_cleanup_meminfo(struct numa_meminfo *mi);
+extern int __init numa_cleanup_meminfo(struct numa_meminfo *mi);
 void __init numa_reset_distance(void);
 
 void __init x86_numa_init(void);
 
-#ifdef CONFIG_NUMA_EMU
-void __init numa_emulation(struct numa_meminfo *numa_meminfo,
-			   int numa_dist_cnt);
-#else
-static inline void numa_emulation(struct numa_meminfo *numa_meminfo,
-				  int numa_dist_cnt)
-{ }
-#endif
+extern void __init numa_emulation(struct numa_meminfo *numa_meminfo,
+				  int numa_dist_cnt);
+
 
 #endif	/* __X86_MM_NUMA_INTERNAL_H */
diff --git a/include/asm-generic/numa.h b/include/asm-generic/numa.h
index 1a3ad6d29833..929d7c582a73 100644
--- a/include/asm-generic/numa.h
+++ b/include/asm-generic/numa.h
@@ -39,6 +39,24 @@ void numa_store_cpu_info(unsigned int cpu);
 void numa_add_cpu(unsigned int cpu);
 void numa_remove_cpu(unsigned int cpu);
 
+struct numa_memblk {
+	u64			start;
+	u64			end;
+	int			nid;
+};
+
+struct numa_meminfo {
+	int			nr_blks;
+	struct numa_memblk	blk[NR_NODE_MEMBLKS];
+};
+
+extern struct numa_meminfo numa_meminfo;
+
+int __init numa_register_memblks(struct numa_meminfo *mi);
+int __init numa_cleanup_meminfo(struct numa_meminfo *mi);
+void __init numa_emulation(struct numa_meminfo *numa_meminfo,
+			   int numa_dist_cnt);
+
 #else	/* CONFIG_NUMA */
 
 static inline void numa_store_cpu_info(unsigned int cpu) { }
diff --git a/mm/Makefile b/mm/Makefile
index ec65984e2ade..6fc1bd7c9f5b 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -138,3 +138,4 @@ obj-$(CONFIG_IO_MAPPING) += io-mapping.o
 obj-$(CONFIG_HAVE_BOOTMEM_INFO_NODE) += bootmem_info.o
 obj-$(CONFIG_GENERIC_IOREMAP) += ioremap.o
 obj-$(CONFIG_SHRINKER_DEBUG) += shrinker_debug.o
+obj-$(CONFIG_NUMA) += numa.o
diff --git a/mm/numa.c b/mm/numa.c
new file mode 100644
index 000000000000..88277e8404f0
--- /dev/null
+++ b/mm/numa.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/acpi.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/memblock.h>
+#include <linux/mmzone.h>
+#include <linux/ctype.h>
+#include <linux/nodemask.h>
+#include <linux/sched.h>
+#include <linux/topology.h>
+
+#include <asm/dma.h>
+
+struct numa_meminfo numa_meminfo __initdata_or_meminfo;
+struct numa_meminfo numa_reserved_meminfo __initdata_or_meminfo;
+
+/*
+ * Set nodes, which have memory in @mi, in *@nodemask.
+ */
+void __init numa_nodemask_from_meminfo(nodemask_t *nodemask,
+					      const struct numa_meminfo *mi)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mi->blk); i++)
+		if (mi->blk[i].start != mi->blk[i].end &&
+		    mi->blk[i].nid != NUMA_NO_NODE)
+			node_set(mi->blk[i].nid, *nodemask);
+}
+
+/**
+ * numa_remove_memblk_from - Remove one numa_memblk from a numa_meminfo
+ * @idx: Index of memblk to remove
+ * @mi: numa_meminfo to remove memblk from
+ *
+ * Remove @idx'th numa_memblk from @mi by shifting @mi->blk[] and
+ * decrementing @mi->nr_blks.
+ */
+static void __init numa_remove_memblk_from(int idx, struct numa_meminfo *mi)
+{
+	mi->nr_blks--;
+	memmove(&mi->blk[idx], &mi->blk[idx + 1],
+		(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);
+}
+
+int __init numa_add_memblk_to(int nid, u64 start, u64 end,
+				     struct numa_meminfo *mi)
+{
+	/* ignore zero length blks */
+	if (start == end)
+		return 0;
+
+	/* whine about and ignore invalid blks */
+	if (start > end || nid < 0 || nid >= MAX_NUMNODES) {
+		pr_warn("Warning: invalid memblk node %d [mem %#010Lx-%#010Lx]\n",
+			nid, start, end - 1);
+		return 0;
+	}
+
+	if (mi->nr_blks >= NR_NODE_MEMBLKS) {
+		pr_err("too many memblk ranges\n");
+		return -EINVAL;
+	}
+
+	mi->blk[mi->nr_blks].start = start;
+	mi->blk[mi->nr_blks].end = end;
+	mi->blk[mi->nr_blks].nid = nid;
+	mi->nr_blks++;
+	return 0;
+}
+
+/**
+ * numa_cleanup_meminfo - Cleanup a numa_meminfo
+ * @mi: numa_meminfo to clean up
+ *
+ * Sanitize @mi by merging and removing unnecessary memblks.  Also check for
+ * conflicts and clear unused memblks.
+ *
+ * RETURNS:
+ * 0 on success, -errno on failure.
+ */
+int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
+{
+	const u64 low = 0;
+	const u64 high = PFN_PHYS(max_pfn);
+	int i, j, k;
+
+	/* first, trim all entries */
+	for (i = 0; i < mi->nr_blks; i++) {
+		struct numa_memblk *bi = &mi->blk[i];
+
+		/* 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);
+
+		/* preserve info for non-RAM areas above 'max_pfn': */
+		if (bi->end > high) {
+			numa_add_memblk_to(bi->nid, high, bi->end,
+					   &numa_reserved_meminfo);
+			bi->end = high;
+		}
+
+		/* and there's no empty block */
+		if (bi->start >= bi->end)
+			numa_remove_memblk_from(i--, mi);
+	}
+
+	/* merge neighboring / overlapping entries */
+	for (i = 0; i < mi->nr_blks; i++) {
+		struct numa_memblk *bi = &mi->blk[i];
+
+		for (j = i + 1; j < mi->nr_blks; j++) {
+			struct numa_memblk *bj = &mi->blk[j];
+			u64 start, end;
+
+			/*
+			 * See whether there are overlapping blocks.  Whine
+			 * about but allow overlaps of the same nid.  They
+			 * will be merged below.
+			 */
+			if (bi->end > bj->start && bi->start < bj->end) {
+				if (bi->nid != bj->nid) {
+					pr_err("node %d [mem %#010Lx-%#010Lx] overlaps with node %d [mem %#010Lx-%#010Lx]\n",
+					       bi->nid, bi->start, bi->end - 1,
+					       bj->nid, bj->start, bj->end - 1);
+					return -EINVAL;
+				}
+				pr_warn("Warning: node %d [mem %#010Lx-%#010Lx] overlaps with itself [mem %#010Lx-%#010Lx]\n",
+					bi->nid, bi->start, bi->end - 1,
+					bj->start, bj->end - 1);
+			}
+
+			/*
+			 * Join together blocks on the same node, holes
+			 * between which don't overlap with memory on other
+			 * nodes.
+			 */
+			if (bi->nid != bj->nid)
+				continue;
+			start = min(bi->start, bj->start);
+			end = max(bi->end, bj->end);
+			for (k = 0; k < mi->nr_blks; k++) {
+				struct numa_memblk *bk = &mi->blk[k];
+
+				if (bi->nid == bk->nid)
+					continue;
+				if (start < bk->end && end > bk->start)
+					break;
+			}
+			if (k < mi->nr_blks)
+				continue;
+			printk(KERN_INFO "NUMA: Node %d [mem %#010Lx-%#010Lx] + [mem %#010Lx-%#010Lx] -> [mem %#010Lx-%#010Lx]\n",
+			       bi->nid, bi->start, bi->end - 1, bj->start,
+			       bj->end - 1, start, end - 1);
+			bi->start = start;
+			bi->end = end;
+			numa_remove_memblk_from(j--, mi);
+		}
+	}
+
+	/* clear unused ones */
+	for (i = mi->nr_blks; i < ARRAY_SIZE(mi->blk); i++) {
+		mi->blk[i].start = mi->blk[i].end = 0;
+		mi->blk[i].nid = NUMA_NO_NODE;
+	}
+
+	return 0;
+}
+
+/*
+ * Mark all currently memblock-reserved physical memory (which covers the
+ * kernel's own memory ranges) as hot-unswappable.
+ */
+static void __init numa_clear_kernel_node_hotplug(void)
+{
+	nodemask_t reserved_nodemask = NODE_MASK_NONE;
+	struct memblock_region *mb_region;
+	int i;
+
+	/*
+	 * We have to do some preprocessing of memblock regions, to
+	 * make them suitable for reservation.
+	 *
+	 * At this time, all memory regions reserved by memblock are
+	 * used by the kernel, but those regions are not split up
+	 * along node boundaries yet, and don't necessarily have their
+	 * node ID set yet either.
+	 *
+	 * So iterate over all memory known to the x86 architecture,
+	 * and use those ranges to set the nid in memblock.reserved.
+	 * This will split up the memblock regions along node
+	 * boundaries and will set the node IDs as well.
+	 */
+	for (i = 0; i < numa_meminfo.nr_blks; i++) {
+		struct numa_memblk *mb = numa_meminfo.blk + i;
+		int ret;
+
+		ret = memblock_set_node(mb->start, mb->end - mb->start, &memblock.reserved, mb->nid);
+		WARN_ON_ONCE(ret);
+	}
+
+	/*
+	 * Now go over all reserved memblock regions, to construct a
+	 * node mask of all kernel reserved memory areas.
+	 *
+	 * [ Note, when booting with mem=nn[kMG] or in a kdump kernel,
+	 *   numa_meminfo might not include all memblock.reserved
+	 *   memory ranges, because quirks such as trim_snb_memory()
+	 *   reserve specific pages for Sandy Bridge graphics. ]
+	 */
+	for_each_reserved_mem_region(mb_region) {
+		int nid = memblock_get_region_node(mb_region);
+
+		if (nid != MAX_NUMNODES)
+			node_set(nid, reserved_nodemask);
+	}
+
+	/*
+	 * Finally, clear the MEMBLOCK_HOTPLUG flag for all memory
+	 * belonging to the reserved node mask.
+	 *
+	 * Note that this will include memory regions that reside
+	 * on nodes that contain kernel memory - entire nodes
+	 * become hot-unpluggable:
+	 */
+	for (i = 0; i < numa_meminfo.nr_blks; i++) {
+		struct numa_memblk *mb = numa_meminfo.blk + i;
+
+		if (!node_isset(mb->nid, reserved_nodemask))
+			continue;
+
+		memblock_clear_hotplug(mb->start, mb->end - mb->start);
+	}
+}
+
+int __weak __init numa_register_memblks(struct numa_meminfo *mi)
+{
+	int i;
+
+	/* Account for nodes with cpus and no memory */
+	node_possible_map = numa_nodes_parsed;
+	numa_nodemask_from_meminfo(&node_possible_map, mi);
+	if (WARN_ON(nodes_empty(node_possible_map)))
+		return -EINVAL;
+
+	for (i = 0; i < mi->nr_blks; i++) {
+		struct numa_memblk *mb = &mi->blk[i];
+		memblock_set_node(mb->start, mb->end - mb->start,
+				  &memblock.memory, mb->nid);
+	}
+
+	/*
+	 * At very early time, the kernel have to use some memory such as
+	 * loading the kernel image. We cannot prevent this anyway. So any
+	 * node the kernel resides in should be un-hotpluggable.
+	 *
+	 * And when we come here, alloc node data won't fail.
+	 */
+	numa_clear_kernel_node_hotplug();
+
+	/*
+	 * If sections array is gonna be used for pfn -> nid mapping, check
+	 * whether its granularity is fine enough.
+	 */
+	if (IS_ENABLED(NODE_NOT_IN_PAGE_FLAGS)) {
+		unsigned long pfn_align = node_map_pfn_alignment();
+
+		if (pfn_align && pfn_align < PAGES_PER_SECTION) {
+			pr_warn("Node alignment %LuMB < min %LuMB, rejecting NUMA config\n",
+				PFN_PHYS(pfn_align) >> 20,
+				PFN_PHYS(PAGES_PER_SECTION) >> 20);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
-- 
2.32.0.3.gf3a3e56d6