From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754774Ab3LEIy5 (ORCPT ); Thu, 5 Dec 2013 03:54:57 -0500 Received: from mail-bk0-f42.google.com ([209.85.214.42]:55713 "EHLO mail-bk0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751791Ab3LEIy4 (ORCPT ); Thu, 5 Dec 2013 03:54:56 -0500 Date: Thu, 5 Dec 2013 09:54:51 +0100 From: Ingo Molnar To: Fenghua Yu Cc: Ingo Molnar , "H. Peter Anvin" , Thomas Gleixner , linux-kernel , x86 Subject: Re: [PATCH] x86/apic: Justification for disabling IO APIC before Local APIC Message-ID: <20131205085451.GA13377@gmail.com> References: <1386202069-51515-1-git-send-email-fenghua.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1386202069-51515-1-git-send-email-fenghua.yu@intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Fenghua Yu wrote: > From: Fenghua Yu > > Since erratum AVR31 in "Intel Atom Processor C2000 Product Family > Specification Update" is published, I add a justification comment for > disabling IO APIC before Local APIC (commit 522e6646). > > Signed-off-by: Fenghua Yu > --- > arch/x86/kernel/reboot.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c > index da3c599..c752cb4 100644 > --- a/arch/x86/kernel/reboot.c > +++ b/arch/x86/kernel/reboot.c > @@ -558,6 +558,17 @@ void native_machine_shutdown(void) > { > /* Stop the cpus and apics */ > #ifdef CONFIG_X86_IO_APIC > + /* > + * Disabling IO APIC before local APIC is a workaround for > + * erratum AVR31 in "Intel Atom Processor C2000 Product Family > + * Specification Update". In this situation, interrupts that target > + * a Logical Processor whose Local APIC is either in the process of > + * being hardware disabled or software disabled are neither delivered > + * nor discarded. When this erratum occurs, the processor may hang. > + * > + * Even without the erratum, it still makes sense to quiet IO APIC > + * before disabling Local APIC. > + */ > disable_IO_APIC(); > #endif Looks good to me, except that patch titles should start with verbs, i.e. something like: x86/apic/doc: Add justification for disabling IO APIC before Local APIC Which makes for a much more fluid reading of shortlogs etc. Unless you sentences without verbs. ^-------------------------------------------like ;-) Thanks, Ingo