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From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Tony Luck <tony.luck@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Fenghua Yu <fenghua.yu@intel.com>, Ingo Molnar <mingo@elte.hu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Asit K Mallick <asit.k.mallick@intel.com>,
	Arjan Dan De Ven <arjan@linux.intel.com>,
	Suresh B Siddha <suresh.b.siddha@intel.com>,
	Len Brown <len.brown@intel.com>,
	"Srivatssa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
	Randy Dunlap <rdunlap@xenotime.net>,
	Chen Gong <gong.chen@linux.intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-pm <linux-pm@vger.kernel.org>, x86 <x86@kernel.org>,
	Peter Zijlstra <peterz@infradead.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()
Date: Fri, 18 May 2012 08:46:01 +0200	[thread overview]
Message-ID: <20120518064601.GC429@gmail.com> (raw)
In-Reply-To: <4FB58143.8060007@zytor.com>


* H. Peter Anvin <hpa@zytor.com> wrote:

> On 05/14/2012 05:17 AM, Ingo Molnar wrote:
> > 
> > * Tony Luck <tony.luck@intel.com> wrote:
> > 
> >> Biggest code impact of that is the extra code to bring cpu0 
> >> back online using NMI instead of INIT. We can't use INIT 
> >> because if cpu0 gets one, it just resets the whole machine :-( 
> >> But obviously we'd like to avoid special cases where there is 
> >> a sane way to do so.
> > 
> > Could we just standardize on NMI bringup during regular bootup?
> > 
> 
> The first instance has to be SIPI because you can't give the 
> CPU an NMI without the IDT being setup.  We *could* assume 
> that the processor is parked in real mode with the valid 
> real-mode IDT set up (in which case the vector at physical 
> address 8 applies) but that seems to assume a lot from the 
> BIOS for little gain.  In particular I suspect that UEFI-based 
> BIOSes may very well park the CPU in protected or long mode.

Ok, fair enough.

Thanks,

	Ingo

  reply	other threads:[~2012-05-18  6:46 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-10 16:16 [PATCH v6 0/12] x86: Arbitrary CPU hot(un)plug support Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 01/12] Documentations/cpu-hotplug.tx, kernel-parameters.txt: Add x86 CPU0 online/offline feature Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 02/12] x86/Kconfig: Add config switch for CPU0 hotplug Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 03/12] x86/topology.c: Support functions for CPU0 online/offline Fenghua Yu
2012-05-10 16:16 ` [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() Fenghua Yu
2012-05-11 12:05   ` Thomas Gleixner
2012-05-11 18:42     ` Tony Luck
2012-05-14 12:17       ` Ingo Molnar
2012-05-14 16:40         ` Luck, Tony
2012-05-14 20:03           ` Yu, Fenghua
2012-05-17 22:47         ` Suresh Siddha
2012-05-18  1:47           ` Yu, Fenghua
2012-05-18  3:34             ` H. Peter Anvin
2012-05-17 22:52         ` H. Peter Anvin
2012-05-18  6:46           ` Ingo Molnar [this message]
2012-05-10 16:16 ` [PATCH v6 05/12] x86/power/cpu.c: Don't hibernate/suspend if CPU0 is offline Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 06/12] x86/head_64.S: Define start_cpu0 Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 07/12] x86/head_32.S: " Fenghua Yu
2012-05-10 17:31   ` H. Peter Anvin
2012-05-10 20:48     ` Yu, Fenghua
2012-05-10 23:53       ` H. Peter Anvin
2012-05-10 16:16 ` [PATCH v6 08/12] x86/smpboot.c: Wake up CPU0 via NMI instead of INITs Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 09/12] x86/common.c: Init CPU0 data during CPU0 online Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 10/12] x86/mtrr/main.c: Ask the first online CPU to save mtrr Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 11/12] x86/i387.c: Thread xstate is initialized only on CPU0 once Fenghua Yu
2012-05-10 16:16 ` [PATCH v6 12/12] x86/topology.c: debug CPU0 hotplug Fenghua Yu

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