linux-kernel - [PATCH] x86/nmi: ratelimit unknown nmi logs

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Date:   Tue, 19 Feb 2019 17:48:36 -0800
From:   Olof Johansson <olof@...om.net>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Olof Johansson <olof@...om.net>
Subject: [PATCH] x86/nmi: ratelimit unknown nmi logs

Getting notified of unknown NMIs is obviously important, but getting
notified on every single one, especially on larger systems with slow
(serial) console causes more harm than good when it's a known noisy
non-relevant event.

So, let's ratelimit to avoid locking up the system.

Signed-off-by: Olof Johansson <olof@...om.net>
---
 arch/x86/kernel/nmi.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 18bc9b51ac9b9..44050cbfee136 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -292,14 +292,14 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 
 	__this_cpu_add(nmi_stats.unknown, 1);
 
-	pr_emerg("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
+	pr_emerg_ratelimited("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
 		 reason, smp_processor_id());
 
-	pr_emerg("Do you have a strange power saving mode enabled?\n");
+	pr_emerg_ratelimited("Do you have a strange power saving mode enabled?\n");
 	if (unknown_nmi_panic || panic_on_unrecovered_nmi)
 		nmi_panic(regs, "NMI: Not continuing");
 
-	pr_emerg("Dazed and confused, but trying to continue\n");
+	pr_emerg_ratelimited("Dazed and confused, but trying to continue\n");
 }
 NOKPROBE_SYMBOL(unknown_nmi_error);
 
-- 
2.11.0