linux-kernel - Re: [PATCH v4 0/7] x86: BSP or CPU0 online/offline

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Date:	Fri, 9 Dec 2011 08:28:17 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	H Peter Anvin <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	"Brown, Len" <len.brown@...el.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v4 0/7] x86: BSP or CPU0 online/offline


* Yu, Fenghua <fenghua.yu@...el.com> wrote:

> > 
> > * Fenghua Yu <fenghua.yu@...el.com> wrote:
> > Then if demand for this picks up some more intelligent method of
> > cooperating with the firmware could be added: the firmware could
> > actually signal to us whether it supports suspend/resume from
> > other than the boot CPU.
> 
> We started to think how to handle the resume issue in 
> firmware, e.g. the way you talked, or change boot CPU to 
> another online CPU to execute resume procedure.
> 
> A firmware solution is a long run. Currently we don't 
> suspend/hibernate when BSP is offline. If a firmware solution 
> is available, we can change the sanity check to allow 
> suspend/hibernate if CPU0 is offline for new firmware. But 
> even when the solution is available in new firmware, we still 
> need to do the same sanity check on legacy firmware.

Right.

You convinced me, if there's no objections i guess we could try 
this feature carefully, if it's named in some more descriptive 
manner such as:

   x86: Arbitrary CPU hot(un)plug support

Nobody outside x86 devs knows 'BSP' means and why they should 
care.

The minor usability/testability/self-test improvements i 
suggested need to be added as well.

Thanks,

	Ingo
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