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Commit 680b6cfd authored by Hidetoshi Seto's avatar Hidetoshi Seto Committed by Ingo Molnar
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x86, mce: CE in last bank prevents panic by unknown MCE 



If MCE handler is called but none of mces_seen have machine
check event which might signal the MCE (i.e. event higher than
MCE_KEEP_SEVERITY), panic with "Machine check from unknown
source" will be taken since the MCE is assumed to be signaled
from external agent or so.

Usually mces_seen never point MCE_KEEP_SEVERITY event such as
CE. But it can happen because initial value of mces_seen is
accidentally modified by mce_no_way_out() - in case if
mce_no_way_out() run through all banks and the last bank has
the CE, mces_seen points the CE and the "panic by unknown" will
not be taken.

This patch fixes this undesired behavior, and clarifies the logic.

Signed-off-by: default avatarHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Dongming <jin.dongming@np.css.fujitsu.com>
LKML-Reference: <4A94E244.3020301@jp.fujitsu.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Reported-by: default avatarJin Dongming <jin.dongming@np.css.fujitsu.com>
parent bf783f9f

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

+4 −4
Original line number Diff line number Diff line
@@ -612,7 +612,7 @@ out: 
 * This way we prevent any potential data corruption in a unrecoverable case

 * and also makes sure always all CPU's errors are examined.

 *

 * Also this detects the case of an machine check event coming from outer

 * Also this detects the case of a machine check event coming from outer

 * space (not detected by any CPUs) In this case some external agent wants

 * us to shut down, so panic too.

 *
@@ -665,7 +665,7 @@ static void mce_reign(void) 
	 * No machine check event found. Must be some external

	 * source or one CPU is hung. Panic.

	 */

	if (!m && tolerant < 3)

	if (global_worst <= MCE_KEEP_SEVERITY && tolerant < 3)

		mce_panic("Machine check from unknown source", NULL, NULL);



	/*
@@ -889,11 +889,11 @@ void do_machine_check(struct pt_regs *regs, long error_code) 
	mce_setup(&m);



	m.mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);

	no_way_out = mce_no_way_out(&m, &msg);



	final = &__get_cpu_var(mces_seen);

	*final = m;



	no_way_out = mce_no_way_out(&m, &msg);



	barrier();



	/*