From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756448Ab3LEDg5 (ORCPT ); Wed, 4 Dec 2013 22:36:57 -0500 Received: from terminus.zytor.com ([198.137.202.10]:38847 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753951Ab3LEDgy (ORCPT ); Wed, 4 Dec 2013 22:36:54 -0500 Date: Wed, 4 Dec 2013 19:36:30 -0800 From: tip-bot for Fenghua Yu Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, fenghua.yu@intel.com, tglx@linutronix.de, hpa@linux.intel.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, fenghua.yu@intel.com, tglx@linutronix.de, hpa@linux.intel.com In-Reply-To: <1386202069-51515-1-git-send-email-fenghua.yu@intel.com> References: <1386202069-51515-1-git-send-email-fenghua.yu@intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/apic, doc: Justification for disabling IO APIC before Local APIC Git-Commit-ID: 2885432aaf15c1b7e65c787bfe7c5fec428296f0 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.1 (terminus.zytor.com [127.0.0.1]); Wed, 04 Dec 2013 19:36:36 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 2885432aaf15c1b7e65c787bfe7c5fec428296f0 Gitweb: http://git.kernel.org/tip/2885432aaf15c1b7e65c787bfe7c5fec428296f0 Author: Fenghua Yu AuthorDate: Wed, 4 Dec 2013 16:07:49 -0800 Committer: H. Peter Anvin CommitDate: Wed, 4 Dec 2013 19:33:21 -0800 x86/apic, doc: Justification for disabling IO APIC before Local APIC Since erratum AVR31 in "Intel Atom Processor C2000 Product Family Specification Update" is now published, I added a justification comment for disabling IO APIC before Local APIC, as changed in commit: 522e66464467 x86/apic: Disable I/O APIC before shutdown of the local APIC Signed-off-by: Fenghua Yu Link: http://lkml.kernel.org/r/1386202069-51515-1-git-send-email-fenghua.yu@intel.com Signed-off-by: H. Peter Anvin --- 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