linux-kernel - Re: [PATCH] x86, mce: short output of MCE banks ownership information

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Date:	Thu, 29 Oct 2009 10:09:57 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
Cc:	Roland Dreier <rdreier@...co.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Mike Travis <travis@....com>
Subject: Re: [PATCH] x86, mce: short output of MCE banks ownership
	information


* Hidetoshi Seto <seto.hidetoshi@...fujitsu.com> wrote:

> Ingo Molnar wrote:
> > * Hidetoshi Seto <seto.hidetoshi@...fujitsu.com> wrote:
> >> Maybe there would be more desirable ways, but I think that "compress 
> >> messages shorter to bear heavy repeating" will be a good way at this 
> >> time.
> > 
> > We really want to only print out relevant information. 128 lines of 
> > identical output is not relevant. (or 2x 64 lines, or 4096 lines of 
> > identical output)
> > 
> > So we only want to print MCE setup messages on the boot CPU. That gives 
> > us 90% of the benefits already: we see the rough structure of the 
> > hardware, and if the bootup has a problem with MCE initialization we get 
> > relevant printouts that helps debugging.
> > 
> > Now, it's certainly true that with things like MCE bank sharing the MCE 
> > setup output from different CPUs might not be identical all the time - 
> > but the information is represented in other (topology) info anyway. (and 
> > if not it wasnt all that important to begin with)
> > 
> > For non-boot CPUs we can perhaps add a mce=verbose (default-disabled) 
> > mode of bootup that allows all CPUs to be printed - should there be any 
> > problem with MCE details only visible on non-boot CPUs. (unlikely)
> 
> How about having a kind of "boot=quiet_ap" which suppress boot-time 
> messages for all non-boot CPUs, rather than "mce=verbose" which only 
> suppress one (or, with thermal message, two) line?  I don't not 
> understand why this problem would be solved only by removing the lines 
> from mce subsystem.

The idea is to suppress bootup messages by default - and to allow opt-in 
verbose printing, in the (rare) case of having to debug bootup problems 
that involve APs.

	Ingo
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