x86, 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).
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Reviewed-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/cpu/mcheck/mce.c

@@ -1269,6 +1269,10 @@ static void mce_cpu_quirks(struct cpuinfo_x86 *c)
 		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;