linux-kernel - [PATCH] mce: don't log boot MCEs on Pentium M (model == 13) CPUs

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Message-Id: <200907282352.55047.bzolnier@gmail.com>
Date:	Tue, 28 Jul 2009 23:52:54 +0200
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] mce: don't log boot MCEs on Pentium M (model == 13) CPUs

From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Subject: [PATCH] mce: don't log boot MCEs on Pentium M (model == 13) CPUs

On my legacy Pentium M laptop (Acer Extensa 2900) I get bogus MCE on a cold
boot with CONFIG_X86_NEW_MCE enabled, i.e. (after decoding it with mcelog):

MCE 0
HARDWARE ERROR. This is *NOT* a software problem!
Please contact your hardware vendor
CPU 0 BANK 1 MCG status:
MCi status:
Error overflow
Uncorrected error
Error enabled
Processor context corrupt
MCA: Data CACHE Level-1 UNKNOWN Error
STATUS f200000000000195 MCGSTATUS 0

[ The other STATUS values observed: f2000000000001b5 (... UNKNOWN error)
  and f200000000000115 (... READ Error).

  To verify that this is not a CONFIG_X86_NEW_MCE bug I also modified
  the CONFIG_X86_OLD_MCE code (which doesn't log any MCEs) to dump
  content of STATUS MSR before it is cleared during initialization. ]

Since the bogus MCE results in a kernel taint (which in turn disables
lockdep support) don't log boot MCEs on Pentium M (model == 13) CPUs
by default ("mce=bootlog" boot parameter can be be used to get the old
behavior).

Cc: Andi Kleen <andi@...stfloor.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: b/arch/x86/kernel/cpu/mcheck/mce.c
===================================================================
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1273,6 +1273,10 @@ static void mce_cpu_quirks(struct cpuinf
 		if ((c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xe)) &&
 			monarch_timeout < 0)
 			monarch_timeout = USEC_PER_SEC;
+
+		/* There are also broken BIOSes on some Pentium M systems. */
+		if (c->x86 == 6 && c->x86_model == 13 && mce_bootlog < 0)
+			mce_bootlog = 0;
 	}
 	if (monarch_timeout < 0)
 		monarch_timeout = 0;
--
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