linux-kernel - [PATCH AUTOSEL 5.15 26/43] s390/topology: honour nr_cpu

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Message-Id: <20230525183854.1855431-26-sashal@kernel.org>
Date:   Thu, 25 May 2023 14:38:37 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Alexander Gordeev <agordeev@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Sasha Levin <sashal@...nel.org>, gor@...ux.ibm.com,
        gregkh@...uxfoundation.org, mcgrof@...nel.org,
        linux-s390@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 26/43] s390/topology: honour nr_cpu_ids when adding CPUs

From: Alexander Gordeev <agordeev@...ux.ibm.com>

[ Upstream commit a33239be2d38ff5a44427db1707c08787508d34a ]

When SMT thread CPUs are added to CPU masks the nr_cpu_ids
limit is not checked and could be exceeded. This leads to
a warning for example if CONFIG_DEBUG_PER_CPU_MAPS is set
and the command line parameter nr_cpus is set to 1.

Reviewed-by: Heiko Carstens <hca@...ux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/s390/kernel/topology.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index 58f8291950cbf..1f4f37a26c26d 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -96,7 +96,7 @@ static void cpu_group_map(cpumask_t *dst, struct mask_info *info, unsigned int c
 static void cpu_thread_map(cpumask_t *dst, unsigned int cpu)
 {
 	static cpumask_t mask;
-	int i;
+	unsigned int max_cpu;
 
 	cpumask_clear(&mask);
 	if (!cpumask_test_cpu(cpu, &cpu_setup_mask))
@@ -105,9 +105,10 @@ static void cpu_thread_map(cpumask_t *dst, unsigned int cpu)
 	if (topology_mode != TOPOLOGY_MODE_HW)
 		goto out;
 	cpu -= cpu % (smp_cpu_mtid + 1);
-	for (i = 0; i <= smp_cpu_mtid; i++) {
-		if (cpumask_test_cpu(cpu + i, &cpu_setup_mask))
-			cpumask_set_cpu(cpu + i, &mask);
+	max_cpu = min(cpu + smp_cpu_mtid, nr_cpu_ids - 1);
+	for (; cpu <= max_cpu; cpu++) {
+		if (cpumask_test_cpu(cpu, &cpu_setup_mask))
+			cpumask_set_cpu(cpu, &mask);
 	}
 out:
 	cpumask_copy(dst, &mask);
@@ -124,25 +125,26 @@ static void add_cpus_to_mask(struct topology_core *tl_core,
 	unsigned int core;
 
 	for_each_set_bit(core, &tl_core->mask, TOPOLOGY_CORE_BITS) {
-		unsigned int rcore;
-		int lcpu, i;
+		unsigned int max_cpu, rcore;
+		int cpu;
 
 		rcore = TOPOLOGY_CORE_BITS - 1 - core + tl_core->origin;
-		lcpu = smp_find_processor_id(rcore << smp_cpu_mt_shift);
-		if (lcpu < 0)
+		cpu = smp_find_processor_id(rcore << smp_cpu_mt_shift);
+		if (cpu < 0)
 			continue;
-		for (i = 0; i <= smp_cpu_mtid; i++) {
-			topo = &cpu_topology[lcpu + i];
+		max_cpu = min(cpu + smp_cpu_mtid, nr_cpu_ids - 1);
+		for (; cpu <= max_cpu; cpu++) {
+			topo = &cpu_topology[cpu];
 			topo->drawer_id = drawer->id;
 			topo->book_id = book->id;
 			topo->socket_id = socket->id;
 			topo->core_id = rcore;
-			topo->thread_id = lcpu + i;
+			topo->thread_id = cpu;
 			topo->dedicated = tl_core->d;
-			cpumask_set_cpu(lcpu + i, &drawer->mask);
-			cpumask_set_cpu(lcpu + i, &book->mask);
-			cpumask_set_cpu(lcpu + i, &socket->mask);
-			smp_cpu_set_polarization(lcpu + i, tl_core->pp);
+			cpumask_set_cpu(cpu, &drawer->mask);
+			cpumask_set_cpu(cpu, &book->mask);
+			cpumask_set_cpu(cpu, &socket->mask);
+			smp_cpu_set_polarization(cpu, tl_core->pp);
 		}
 	}
 }
-- 
2.39.2