linux-kernel - [PATCH] x86: Fix /proc/cpuinfo cpumask warning

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Message-Id: <20221011175031.1782748-1-ajones@ventanamicro.com>
Date:   Tue, 11 Oct 2022 19:50:31 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Yury Norov <yury.norov@...il.com>
Subject: [PATCH] x86: Fix /proc/cpuinfo cpumask warning

Upcoming cpumask changes will start issuing warnings[*] when cpu
indices equal to nr_cpu_ids are passed to cpumask_next* functions.
Ensure we don't generate a warning when reading /proc/cpuinfo by
validating the cpu index before calling cpumask_next().

[*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled.

Signed-off-by: Andrew Jones <ajones@...tanamicro.com>
Cc: Yury Norov <yury.norov@...il.com>
---
 arch/x86/kernel/cpu/proc.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index 099b6f0d96bd..584ae6cb5b87 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -153,9 +153,12 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 
 static void *c_start(struct seq_file *m, loff_t *pos)
 {
-	*pos = cpumask_next(*pos - 1, cpu_online_mask);
-	if ((*pos) < nr_cpu_ids)
-		return &cpu_data(*pos);
+	if (*pos < nr_cpu_ids) {
+		*pos = cpumask_next(*pos - 1, cpu_online_mask);
+		if (*pos < nr_cpu_ids)
+			return &cpu_data(*pos);
+	}
+
 	return NULL;
 }
 
-- 
2.37.3