From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760744Ab1LQCCZ (ORCPT ); Fri, 16 Dec 2011 21:02:25 -0500 Received: from mga09.intel.com ([134.134.136.24]:33662 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754150Ab1LQCCR (ORCPT ); Fri, 16 Dec 2011 21:02:17 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,352,1309762800"; d="scan'208";a="87515340" Subject: Re: [PATCH -v8] x86: Disable x2apic if nox2apic is specified or intr-remap can not be enabled From: Suresh Siddha Reply-To: Suresh Siddha To: Yinghai Lu Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" Date: Fri, 16 Dec 2011 18:07:03 -0800 In-Reply-To: <1324083546-1003-1-git-send-email-yinghai@kernel.org> References: <1324083546-1003-1-git-send-email-yinghai@kernel.org> Organization: Intel Corp Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.0.3 (3.0.3-1.fc15) Content-Transfer-Encoding: 7bit Message-ID: <1324087625.1984.296.camel@sbsiddha-desk.sc.intel.com> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-12-16 at 16:59 -0800, Yinghai Lu wrote: > For > 1. x2apic preenabled system > 2. first kernel have x2apic enabled, and try to kexec second kernel with "nox2apic" > > Will put back cpu with apic id < 255 into xapic mode, instead of panic. > Yinghai, I didn't get a chance to review this patch completely. But few things. a. Need to split this patch into multiple patches, specially the cpuid mechanism to get the initial apic id, flat_probe etc. While I understand the reason behind the flat_probe change, it isn't quite obvious from this changelog. b. for nox2apic, as you try to disable x2apic even if the bios has enabled it along with interrupt-remapping, this will probably not work unless we disable interrupt-remapping. So either we need to ignore the nox2apic when OS can find that interrupt-remapping is already enabled or disable interrupt-remapping. Let me think a bit more about this and get back to you by monday with detailed review of this. thanks, suresh