From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753162Ab1LLHYB (ORCPT ); Mon, 12 Dec 2011 02:24:01 -0500 Received: from mga01.intel.com ([192.55.52.88]:5923 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752110Ab1LLHYA (ORCPT ); Mon, 12 Dec 2011 02:24:00 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.71,315,1320652800"; d="scan'208";a="95096270" Subject: Re: x2apic boot failure on recent sandy bridge system From: Suresh Siddha Reply-To: Suresh Siddha To: Yinghai Lu Cc: Ingo Molnar , "Berck E. Nash" , "linux-kernel@vger.kernel.org" In-Reply-To: References: <4EE2BC33.80902@gmail.com> <20111211075713.GA20790@elte.hu> Content-Type: text/plain; charset="UTF-8" Organization: Intel Date: Sun, 11 Dec 2011 23:23:22 -0800 Message-ID: <1323674602.4170.5.camel@sbsiddha-mobl2> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2011-12-11 at 13:43 -0800, Yinghai Lu wrote: > -v4: according to Ingo, for x2apic pre-enabled system, if intr-remap can not > be enabled, try to disable x2apic instead of panic and request to > specify nox2apic for next boot. If bios has not exported any DMAR tables but enabled x2apic pre-boot, it is tricky for the OS to disable x2apic and continue with xapic for number of reasons. For example, if chipset has already enabled interrupt-remapping (which is typically recommended to be enabled before x2apic) but didn't provide DMAR tables, then there is no way OS can disable interrupt-remapping in this case. So even though the cpu might be back in xapic mode, but external interrupts won't work. thanks, suresh