linux-kernel - Re: [PATCH v3] x86/mce: Honour bios-set CMCI threshold

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Date:	Wed, 17 Oct 2012 20:09:09 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Borislav Petkov <bp@...en8.de>,
	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	"gong.chen@...ux.intel.com" <gong.chen@...ux.intel.com>,
	"ananth@...ibm.com" <ananth@...ibm.com>,
	"masbock@...ux.vnet.ibm.com" <masbock@...ux.vnet.ibm.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lcm@...ibm.com" <lcm@...ibm.com>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
Subject: Re: [PATCH v3] x86/mce: Honour bios-set CMCI threshold

On Wed, Oct 17, 2012 at 05:28:11PM +0000, Luck, Tony wrote:
> > What's wrong with userspace tools parsing /proc/cmdline and seeing that
> > mce_bios_cmci_threshold has been set since this is the only way to set
> > it anyway?
> 
> The argument might be on the command line, but may have been rejected
> because the BIOS didn't set the thresholds? So then you'd have to look at
> the command line, *and* check /var/log/messages to make sure we hadn't
> printed the message saying the BIOS was unsupportive.

Right, but the sysfs read-only thing doesn't solve that either - it only
dumps the mce_bios_cmci_threshold value so it doesn't help.

The stuff you're talking about is not reflected in that variable but
saved in some other like bios_wrong_thresh and bios_zero_thresh.

> BUT ... I don't think that knowing this is sufficient. A userspace
> tool would want to know what value had been set for each bank. So if
> it really wants to do something interesting, just knowing that "bios
> set some thresholds" doesn't sound like enough information.

Yes. And I still haven't gotten a real use case of what userspace tool
will do with this information.

> BUT (squared) do you even really need to know that thresholds were
> set? You could look at bits {52:38} in the MCi_STATUS information for
> the bank to see how many corrected errors had been logged.

Right, a real use case which shows why we need that information should
be good.

Thanks.

> -Tony
> .�{.n�+�������+%��lzwm��b�맲��r��zX��.�iȧ�.��ܨ}���Ơz�&j:+v���.����zZ+��+zf���h���~����i���z�.�w���?����&�)ߢ.f

What happened here? It seems your mail client wanted to say something
too but it has been censored.

:-)

-- 
Regards/Gruss,
Boris.

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