x86: Do not panic if mce=2 is passed

From: Yinghai Lu <[email protected]>

For UE recovery support, current we need mce=2 in command line and also disable panic_on_oops with sysctl.

but other user may still need to have panic_on_oops to 1 always.

We can remove checking of panic_on_oops for mce-severity path.

We should be ok as on default path when mce=2 is not passed, tolerant is 0, so they will still get MCE_PANIC_SEVERITY returned.

---
 arch/x86/kernel/cpu/mcheck/mce-severity.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/arch/x86/kernel/cpu/mcheck/mce-severity.c
===================================================================
@@ -311,7 +311,7 @@ static int mce_severity_intel(struct mce
 			*msg = s->msg;
 		s->covered = 1;
 		if (s->sev >= MCE_UC_SEVERITY && ctx == IN_KERNEL) {
-			if (panic_on_oops || tolerant < 1)
+			if (tolerant < 1)
 				return MCE_PANIC_SEVERITY;
 		}
 		return s->sev;

Please explain. I've never given mce=2 on command line, and have had my kernel recover from thousands of (injected) UE memory errors.

-Tony

So frankly, that panic_on_oops doesn't make a whole lotta sense to me.

It is promoting MCEs with severity MCE_UC_SEVERITY and higher to a panic.

So let's look at those:

MCE_UC_SEVERITY, - we don't do anything special in the kernel for
those so just as well.
MCE_AR_SEVERITY, - those end up in the memory failure code if
they're memory errors
MCE_PANIC_SEVERITY, - causes panic

so if anything, panic_on_oops shouldn't control the panicking behavior as tolerant does that already:

* Tolerant levels:
* 0: always panic on uncorrected errors, log corrected errors
* 1: panic or SIGBUS on uncorrected errors, log corrected errors
* 2: SIGBUS or log uncorrected errors (if possible), log corr. errors
* 3: never panic or SIGBUS, log all errors (for testing only)

IOW, I think that patch makes sense but please doublecheck my logic above first.

Thanks.

Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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