linux-kernel - RE: [PATCH v1 0/2] x86, apic: Disable BSP if boot cpu is AP

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Message-ID: <3E5A0FA7E9CA944F9D5414FEC6C7122030B0DD91@ORSMSX105.amr.corp.intel.com>
Date:	Tue, 16 Oct 2012 05:14:46 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"x86@...nel.org" <x86@...nel.org>, "mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"Brown, Len" <len.brown@...el.com>,
	"vgoyal@...hat.com" <vgoyal@...hat.com>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>
Subject: RE: [PATCH v1 0/2] x86, apic: Disable BSP if boot cpu is AP

> >> My motivation is to use multiple CPUs in order to quickly generate
> >> crash dump on the machine with huge amount of memory. I assume such
> >> machine tends to also have a lot of CPUs. So disabling one CPU would
> >> be no problem.
> >
> > Luckily you don't need to disable any CPU to archive your goal with
> > the BSP hotplug pachest:)
> >
> > On a dual core/single thread machine, this means you get 100%
> performance
> > boost with BSP's help.
> >
> > Plus crash dump kernel code is better structured by not treating BSP
> > specially.
> >
> 
> Hello Fenghua.
> 
> I've of course noticed your patch set and locally tested, but I saw
> NMI to BSP failed in the 2nd kernel. I'll send a log to you later.
> 
> BTW, I tested with your previous v8 patch set. Did you change
> something during v8 to v9 relevant to this issue?

In the patch 0/12 in v9, I describe what change is in v9 on the top of v8:

v9: Add Intel vendor check to support the feature on Intel platforms only.

Did you see the BSP wake up failure on the latest tip tree?

There is a rcu regression issue which prevents BSP from waking up in 3.6.0.
The issue has been fixed on 10/12. The commit is a4fbe35a. Please make sure
your tip tree has this commit.

Thanks.

-Fenghua


Thanks.

-Fenghua
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