From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751618Ab1KDX2A (ORCPT ); Fri, 4 Nov 2011 19:28:00 -0400 Received: from oproxy1-pub.bluehost.com ([66.147.249.253]:39136 "HELO oproxy1-pub.bluehost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751216Ab1KDX16 (ORCPT ); Fri, 4 Nov 2011 19:27:58 -0400 Message-ID: <4EB474CA.1080709@xenotime.net> Date: Fri, 04 Nov 2011 16:27:06 -0700 From: Randy Dunlap Organization: YPO4 User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110323 Thunderbird/3.1.9 MIME-Version: 1.0 To: Fenghua Yu CC: Thomas Gleixner , H Peter Anvin , Ingo Molnar , Linus Torvalds , Andrew Morton , Tony Luck , Suresh B Siddha , Len Brown , "Srivatsa S. Bhat" , Peter Zijlstra , linux-kernel Subject: Re: [PATCH 9/9] Documentations/cpu-hotplug.tx, kernel-parameters.txt: Add x86 CPU0 online/offline feature References: <1320444241-834-1-git-send-email-fenghua.yu@intel.com> <1320444241-834-10-git-send-email-fenghua.yu@intel.com> In-Reply-To: <1320444241-834-10-git-send-email-fenghua.yu@intel.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Identified-User: {1807:box742.bluehost.com:xenotime:xenotime.net} {sentby:smtp auth 50.53.38.135 authed with rdunlap@xenotime.net} Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/04/2011 03:04 PM, Fenghua Yu wrote: > From: Fenghua Yu > > Add x86 CPU0 online/offline feature in the two documentations. > > By default BSP is not pluggable. Kernel parameter bsp_hotplug enables BSP > online/offline feature. > > The documentations point out two BSP dependencies. First, resume from hibernate > or suspend always starts from BSP. So hibernate and suspend are prevented if BSP > is offline. Another dependency is PIC interrupts always go to BSP. > > Signed-off-by: Fenghua Yu > --- > --- > Documentation/cpu-hotplug.txt | 19 +++++++++++++++++++ > Documentation/kernel-parameters.txt | 13 +++++++++++++ > 2 files changed, 32 insertions(+), 0 deletions(-) > > diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt > index a20bfd4..ebd41e7 100644 > --- a/Documentation/cpu-hotplug.txt > +++ b/Documentation/cpu-hotplug.txt > @@ -207,6 +207,25 @@ by making it not-removable. > > In such cases you will also notice that the online file is missing under cpu0. > > +Q: Is CPU0 removable on X86? > +A: Yes. If given kernel option bsp_hotplug, CPU0 is removable. > + > +But some features may depend on BSP. Known dependencies are: Drop "may". > +1. Hibernate/suspend depends on BSP. Hibernate/suspend will fail if BSP is > +offline and you need to online BSP before hibernate/suspend can continue. > +2. PIC interrupts also depend on BSP. BSP can't be removed if a PIC interrupt > +is detected. > + > +It's said poweroff/reboot may depend on BSP on some machines although I haven't > +seen any poweroff/reboot failure so far after BSP is offline on a few tested > +machines. > + > +Please let me know if you know or see any other dependencies of BSP. > + > +If the dependencies are under your control, you can turn on bsp_hotplug. > + > +--Fenghua Yu > + > Q: How do i find out if a particular CPU is not removable? > A: Depending on the implementation, some architectures may show this by the > absence of the "online" file. This is done if it can be determined ahead of > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index a0c5c5f..b1c7e68 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -1842,6 +1842,19 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > > nox2apic [X86-64,APIC] Do not enable x2APIC mode. > > + bsp_hotplug [X86] BSP (aka CPU0) is hotpluggable. > + Some features may depend on BSP. Known dependencies are Drop "may". Then add ":" after "are". I.e., Some features depend on BSP. Known dependencies are: > + 1. Suspend/resume depends on BSP. Suspend will fail if > + BSP is offline and you need to online BSP before > + suspend/resume. > + 2. PIC interrupts also depend on BSP. BSP can't be > + removed if a PIC interrupt is detected. > + It's said poweroff/reboot may depend on BSP on some > + machines although I haven't seen such issues so far > + after BSP is offline on a few tested machines. > + If the dependencies are under your control, you can > + turn on bsp_hotplug. > + > nptcg= [IA-64] Override max number of concurrent global TLB > purges which is reported from either PAL_VM_SUMMARY or > SAL PALO. -- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code ***