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Date: Fri, 19 Apr 2013 10:44:28 +0200
From: Ingo Molnar <mingo@kernel.org>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>, Robin Holt <holt@sgi.com>,
        Ingo Molnar <mingo@redhat.com>, Russ Anderson <rja@sgi.com>,
        Shawn Guo <shawn.guo@linaro.org>, Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Paul Mackerras <paulus@samba.org>,
        Peter Zijlstra <peterz@infradead.org>,
        "rusty@rustcorp.com.au" <rusty@rustcorp.com.au>,
        Tejun Heo <tj@kernel.org>, the arch/x86 maintainers <x86@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Fenghua Yu <fenghua.yu@intel.com>
Subject: Re: [Patch -v4 1/4] Migrate shutdown/reboot to boot cpu.
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* Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> wrote:

> On 04/19/2013 01:26 PM, Ingo Molnar wrote:
> > 
> > * Borislav Petkov <bp@alien8.de> wrote:
> > 
> >> On Wed, Apr 17, 2013 at 09:46:53AM +0200, Ingo Molnar wrote:
> >>
> >>> What you mention here should indeed already be handled by the architecture 
> >>> hotplug code (for example on x86 the boot CPU cannot be hot-removed).
> >>
> >> Supposedly, some new Intels (I think Ivybridge or so) can actually be 
> >> hot-removed.
> > 
> > There are WIP patches in existence that remove the limitations on the kernel side, 
> > but they are not upstream yet, so currently the constraint exists upstream.
> > 
> 
> I thought Fenghua Yu's upstream commits were supposed to handle that. Don't they?

Hm, I thought there were more patches needed to support actual hardware - the 
feature also has various limitations related suspend/resume. Are these 
CPU0-hotplug commits all that was needed to support the new hot-pluggable 
hardware?

In any case, you are right - it's indeed possible upstream as well.

Thanks,

	Ingo