linux-kernel - Re: [PATCH v2 1/2] x86: mce: kexec: turn off MCE in kexec

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Date:	Fri, 27 Feb 2015 21:46:16 +0900
From:	Naoya Horiguchi <nao.horiguchi@...il.com>
To:	Prarit Bhargava <prarit@...hat.com>
CC:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Tony Luck <tony.luck@...el.com>,
	Borislav Petkov <bp@...en8.de>,
	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Junichi Nomura <j-nomura@...jp.nec.com>,
	Kiyoshi Ueda <k-ueda@...jp.nec.com>
Subject: Re: [PATCH v2 1/2] x86: mce: kexec: turn off MCE in kexec

Hi Prarit,

On Fri, Feb 27, 2015 at 06:09:52AM -0500, Prarit Bhargava wrote:
...
> > @@ -157,6 +160,11 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
> >  	/* The kernel is broken so disable interrupts */
> >  	local_irq_disable();
> >
> > +	/*
> > +	 * We can't expect MCE handling to work any more, so turn it off.
> > +	 */
> > +	cpu_emergency_mce_disable();
>
> What if the system is actually having problems with MCE errors -- which are
> leading to system panics of some sort.  Do you *really* want the system to
> continue on at that point?

Yes, when running the above code, the system doesn't run any business logic,
so no worry about consuming broken data caused by HW errors.
And what we really want to get is any kind of information to find out what
caused the 1st panic, which are likely to be contained in kdump data.
So I think it's justified to improve the success rate of kdump by continuing
the operation here.

Thanks,
Naoya Horiguchi
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