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Subject: RE: [PATCH 0/8] Online/offline BSP on x86
From: Peter Zijlstra <peterz@infradead.org>
To: "Yu, Fenghua" <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        H Peter Anvin <hpa@zytor.com>, "Luck, Tony" <tony.luck@intel.com>,
        "Mallick, Asit K" <asit.k.mallick@intel.com>,
        "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
        "Brown, Len" <len.brown@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
Date: Wed, 05 Oct 2011 22:37:47 +0200
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On Wed, 2011-10-05 at 13:29 -0700, Yu, Fenghua wrote:
> > Yes, I got that part. Why do you care?
> 
> I can think of two reasons for bsp offline/online:
> 
> 1. RAS needs the feature. If socket0 needs to be hotplugged for any
> reason (any thread on socket0 is bad, shared cache issue, uncore
> issue, etc), CPU0 is required to be offlined.
> 
Right, this is what I asked.

> 2. CPU0 is symmetrical to other CPU's. There is no specific reason why
> it shouldn't be offlined except BIOS requirements. 

Right, so how are you going to deal with crappy BIOS stuffs? We all know
there's plenty of that around.