linux-kernel - Re: [PATCH 4/8] x86, mce: rename bootparam parser

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Date:	Sat, 18 Jun 2011 10:38:20 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"Luck, Tony" <tony.luck@...el.com>
Cc:	Borislav Petkov <bp@...64.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 4/8] x86, mce: rename bootparam parser

On Fri, Jun 17, 2011 at 03:25:51PM -0700, Luck, Tony wrote:
> > and leave this like this. "nomce" is the same as "mce=off" and frankly,
> > I'd like to remove this redundancy, thus no need to do the code
> > relocation. In addition, I don't think there are lots of systems running
> > with "nomce" so I really think we should drop it.
> >
> > So Ingo, hpa, what is the proper way to remove early setup params? Maybe
> > through Documentation/feature-removal-schedule.txt?
> 
> Though it seems odd to me that anyone would want to turn mce off,
> the fact that we have two ways to do so would indicate that people
> do (or at least did) want to do this.

Yeah, the only usecase I could think of for this is people doing their
own userspace DRAM ECC evaluation like google. But they'd still need to
have an #MC handler... or they could parse syslog for the output from
the default unexpected_machine_check().. hm.

> It seems like we'd need a long "deprecated" period (till all the
> major OSVs turn out a new release) to remove this without surprises.
> If the "nomce" option just disappears, then people using it will
> not realize that their boot time argument was ignored (until they
> see a reported error).

Yeah, we could do a grace period with a warning:

/*
 * Old style boot options parsing. Only for compatibility.
 */
static int __init mcheck_disable(char *str)
{
	pr_err("\"nomce\" boot param is deprecated. Please use \"mce=off\"\n");

	mce_disabled = 1;
	return 1;
}
__setup("nomce", mcheck_disable);

and then kill it.

-- 
Regards/Gruss,
    Boris.
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