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

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Message-ID: <54F494E9.4020307@redhat.com>
Date:	Mon, 02 Mar 2015 11:50:49 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Naoya Horiguchi <nao.horiguchi@...il.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	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



On 03/02/2015 11:32 AM, Borislav Petkov wrote:
> On Mon, Mar 02, 2015 at 11:33:33PM +0900, Naoya Horiguchi wrote:
>> Yes, CPU offlining is one option to keep other CPUs quiet. I'm not sure why
>> current kexec implementation doesn't offline the other CPUs but just doing
>> cpu_relax() loop, but my guess is that in some kernel panic situation (like
>> soft lockup) we want to keep CPUs' status undisturbed to make sure the bug's
>> info is captured in kdump.
> 
> Well either offlining or keeping them in the idle loop is fine - they're
> not executing anything else and thus the probability of them causing an
> MCE becomes disappearingly small.

Unless entering a deep C state kicks an MCE ... which we've seen with flaky
hardware.

P.

> 
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