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Subject[PATCH v2 1/5] mm: Enable CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA
Date
In NUMA layout which nodes have memory ranges that span across other nodes,
the mm driver can detect the memory node id incorrectly.

For example, with layout below
Node 0 address: 0000 xxxx 0000 xxxx
Node 1 address: xxxx 1111 xxxx 1111

Note:
- Memory from low to high
- 0/1: Node id
- x: Invalid memory of a node

When mm probes the memory map, without CONFIG_NODES_SPAN_OTHER_NODES
config, mm only checks the memory validity but not the node id.
Because of that, Node 1 also detects the memory from node 0 as below
when it scans from the start address to the end address of node 1.

Node 0 address: 0000 xxxx xxxx xxxx
Node 1 address: xxxx 1111 1111 1111

This layout could occur on any architecture. This patch enables
CONFIG_NODES_SPAN_OTHER_NODES by default for NUMA to fix this issue.

Signed-off-by: Hoan Tran <Hoan@os.amperecomputing.com>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d66bc8a..6335505 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1413,7 +1413,7 @@ int __meminit early_pfn_to_nid(unsigned long pfn)
}
#endif

-#ifdef CONFIG_NODES_SPAN_OTHER_NODES
+#ifdef CONFIG_NUMA
/* Only safe to use early in boot when initialisation is single-threaded */
static inline bool __meminit early_pfn_in_nid(unsigned long pfn, int node)
{
--
2.7.4
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