linux-kernel - Re: [PATCH v6 04/12] x86/smpboot.c: Don't offline CPU0 if any irq can not be migrated out of it and remove CPU0 check in smp

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Message-ID: <4FB5C347.6010105@zytor.com>
Date:	Thu, 17 May 2012 20:34:31 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>
CC:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Mallick, Asit K" <asit.k.mallick@...el.com>,
	Arjan Dan De Ven <arjan@...ux.intel.com>,
	"Brown, Len" <len.brown@...el.com>,
	"Srivatssa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Chen Gong <gong.chen@...ux.intel.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...r.kernel.org>, x86 <x86@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v6 04/12] x86/smpboot.c: Don't offline CPU0 if any irq
 can not be migrated out of it and remove CPU0 check in smp_callin()

On 05/17/2012 06:47 PM, Yu, Fenghua wrote:
> 
> Then booting up AP via INIT and putting AP online back via NMI/mwait
> will have different wakeup method and code. We probably need a way to
> tell if it is first AP bringup or online AP/BSP during run time.
> 
> And if offlined CPU is not in mwait (e.g. CPU without mwait feature),
> mwait based bringup won't work. Do we need to fall back to NMI wakeup
> if offlined CPU is not in mwait?
> 

I guess we need NMI (or just re-SIPI) in that case, since we're spinning
in CLI; HLT...

	-hpa


-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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