From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756114Ab3LEAJE (ORCPT ); Wed, 4 Dec 2013 19:09:04 -0500 Received: from mga02.intel.com ([134.134.136.20]:33902 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753140Ab3LEAJB (ORCPT ); Wed, 4 Dec 2013 19:09:01 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.93,829,1378882800"; d="scan'208";a="447063161" From: "Fenghua Yu" To: "Ingo Molnar" , "H. Peter Anvin" , "Thomas Gleixner" Cc: "linux-kernel" , "x86" , "Fenghua Yu" Subject: [PATCH] x86/apic: Justification for disabling IO APIC before Local APIC Date: Wed, 4 Dec 2013 16:07:49 -0800 Message-Id: <1386202069-51515-1-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 1.8.0.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 -- 1.8.1.2