Re: [PATCH 2/2] selftests/mm: fix ksm NUMA merge test for systems with memoryless NUMA nodes

["David Hildenbrand (Arm)" <david@kernel.org>]

>  
> +static int count_mem_nodes(void)
> +{
> +	int node, count = 0;
> +
> +	for (node = 0; node <= numa_max_node(); node++) {
> +		if (numa_node_size(node, NULL) > 0)
> +			count++;
> +	}
> +
> +	return count;
> +}
> +

Can we instead build upon our existing helpers get_first_mem_node() +
get_next_mem_node() ?

From 432774fb50237519c1c041e402fddfdf4b35aa2c Mon Sep 17 00:00:00 2001
From: "David Hildenbrand (Arm)" <david@kernel.org>
Date: Fri, 26 Jun 2026 17:52:21 +0200
Subject: [PATCH] tmp

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 tools/testing/selftests/mm/ksm_tests.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
index a050f4840cfa3..2ebbb544c6711 100644
--- a/tools/testing/selftests/mm/ksm_tests.c
+++ b/tools/testing/selftests/mm/ksm_tests.c
@@ -440,9 +440,9 @@ static int get_next_mem_node(int node)
 		mem_node = i % (max_node + 1);
 		node_size = numa_node_size(mem_node, NULL);
 		if (node_size > 0)
-			break;
+			return mem_node;
 	}
-	return mem_node;
+	return -ENODEV;
 }
 
 static int get_first_mem_node(void)
@@ -455,8 +455,8 @@ static int check_ksm_numa_merge(int merge_type, int mapping, int prot, int timeo
 {
 	void *numa1_map_ptr, *numa2_map_ptr;
 	struct timespec start_time;
+	int first_node, second_node;
 	int page_count = 2;
-	int first_node;
 
 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
 		ksft_perror("clock_gettime");
@@ -467,17 +467,19 @@ static int check_ksm_numa_merge(int merge_type, int mapping, int prot, int timeo
 		ksft_print_msg("NUMA support not enabled\n");
 		return KSFT_SKIP;
 	}
-	if (numa_num_configured_nodes() <= 1) {
-		ksft_print_msg("At least 2 NUMA nodes must be available\n");
+	first_node = get_first_mem_node();
+	second_node = get_next_mem_node(first_node);
+
+	if (second_node < 0) {
+		ksft_print_msg("At least 2 NUMA nodes with memory must be available\n");
 		return KSFT_SKIP;
 	}
 	if (ksm_write_sysfs(KSM_FP("merge_across_nodes"), merge_across_nodes))
 		return KSFT_FAIL;
 
 	/* allocate 2 pages in 2 different NUMA nodes and fill them with the same data */
-	first_node = get_first_mem_node();
 	numa1_map_ptr = numa_alloc_onnode(page_size, first_node);
-	numa2_map_ptr = numa_alloc_onnode(page_size, get_next_mem_node(first_node));
+	numa2_map_ptr = numa_alloc_onnode(page_size, second_node);
 	if (!numa1_map_ptr || !numa2_map_ptr) {
 		ksft_perror("numa_alloc_onnode");
 		return KSFT_FAIL;
-- 
2.43.0


-- 
Cheers,

David