linux-kernel - Re: [PATCH 1/3] mce: Add a msg string to the MCE tracepoint

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Date:	Wed, 29 Feb 2012 15:00:35 -0300
From:	Mauro Carvalho Chehab <mchehab@...hat.com>
To:	"Luck, Tony" <tony.luck@...el.com>
CC:	Borislav Petkov <bp@...64.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	EDAC devel <linux-edac@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mce: Add a msg string to the MCE tracepoint

Em 29-02-2012 14:20, Luck, Tony escreveu:
>> IMHO, before removing those fields, it would be better to first implement
>> what is there at the mcelog userspace parser for the Intel machines into
>> kernelspace (or to look into its source code), and check what registers
>> aren't used by either AMD 64 MCE decoder or by the Intel MCE decoder.
>>
>> Tony,
>>
>> Is there anyone at Intel working on porting it to kernelspace?
> 
> The mcelog code just looks at model specific fields in MCi_STATUS
> and MCi_MISC.  We could move it to the kernel - but I don't see
> much value in doing so. 

I see a few reasons:

	- it would be consistent with what's being done at AMD. So, all x86
	  arch will report errors at the same way;

	- userspace won't need to run an extra daemon/tool to decode the
	  errors;

	- fatal errors won't be lost (well, in fact, you have there already 
	  a parser for fatal errors. Not sure if all possible fatal errors
	  are covered here, nor what else is needed, as you have already 
	  there part of mcelog decoder);

	- a single place to maintain, when new cpu families are added;

	- it makes easier to centralize the hardware error information,
	  as there's no need to enrich the error on userspace.

> In this case all the information we need
> is carried in status/misc - so as long as we keep all of those
> bits (and the cpu family/model) we can safely decode/analyze later.

Hmm... the mcelog tool opens the /proc/cpuinfo:

$ grep cpuinfo *
mcelog.c:	f = fopen("/proc/cpuinfo","r");
mcelog.c:			Eprintf("warning: Cannot parse /proc/cpuinfo\n"); 
mcelog.c:		Eprintf("warning: Cannot open /proc/cpuinfo\n");
tsc.c:	asprintf(&fn, "/sys/devices/system/cpu/cpu%d/cpufreq/cpuinfo_max_freq", cpu);
tsc.c:		/* /sys exists, but no cpufreq -- use value from cpuinfo */

That probably means that the needed cpu family/model info is not (or may not) be
stored at the MCE structure.

> 
> -Tony

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