linux-kernel - Re: [HW PROBLEM] Intel I7 MCE. Erratum or not?

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Message-ID: <493CCFE4.2080802@jp.fujitsu.com>
Date:	Mon, 08 Dec 2008 16:42:28 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Giangiacomo Mariotti <gg.mariotti@...il.com>
CC:	Arjan van de Ven <arjan@...radead.org>,
	Robert Hancock <hancockr@...w.ca>,
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [HW PROBLEM] Intel I7 MCE. Erratum or not?

Giangiacomo Mariotti wrote:
> I noticed something else, which though may be due to my inexperience
> with mce messages. In my directory /sys/devices/system/machinecheck
> there are machinecheck0-7(one for each logical cpu of my system I
> presume). Having received the MCE log always for cpu 0, I went to look
> inside dir machinecheck0 and I found bank0-5ctl. So now my question
> is, why do I receive MCE logs about bank 6, if my cpus don't have a
> bank 6? Does that count start from 1? Or am I missing something else?

Answer would be in the following commit:

> commit 8edc5cc5ec880c96de8e6686fb0d7a5231e91c05
> Author: Venki Pallipadi <venkatesh.pallipadi@...el.com>
> Date:   Mon May 12 15:43:34 2008 +0200
> 
>     x86: remove 6 bank limitation in 64 bit MCE reporting code
(snip)
>     The patch below does not create sysfs control (bankNctl) for banks
>     higher than 6 as well. That needs some pre-cleanup in /sysfs mce layout,
>     removal of per cpu /sysfs entries for bankctl as they are really global
>     system level control today. That change will follow. This basic change
>     is critical to report the detailed errors on banks higher than 6.

So there are 6 sysfs control(bank0-5ctl) even if your cpu have more banks.

Old kernel with bank limitation will say:
"MCE: warning: using only %d banks\n"
And it seems that old kernel will ignore records in banks higher than 6.

Thanks,
H.Seto

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