From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756682AbZBSLah (ORCPT ); Thu, 19 Feb 2009 06:30:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751526AbZBSLa3 (ORCPT ); Thu, 19 Feb 2009 06:30:29 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:58778 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751329AbZBSLa2 (ORCPT ); Thu, 19 Feb 2009 06:30:28 -0500 Date: Thu, 19 Feb 2009 12:30:18 +0100 From: Ingo Molnar To: Gleb Natapov Cc: linux-kernel@vger.kernel.org, yinghai@kernel.org, "H. Peter Anvin" , Thomas Gleixner Subject: Re: [PATCH] decouple x2apic from irq remapping Message-ID: <20090219113018.GS2354@elte.hu> References: <20090218120051.GF26845@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090218120051.GF26845@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Gleb Natapov wrote: > Hi, > > Currently x2apic is used only if interrupt remapping can be enabled, > but if all apic ids are smaller then 255 there is no reason to > enable interrupt remapping at all. Although there is not real HW that has > x2apic but does not have IR the decoupling is useful since we want to > emulate x2apic interface in KVM (it is more vitalization friendly), but > we don't want to emulate IR just for that. > > According to Intel docs BIOS should pass control to OS in x2apic mode > if there are apics with id > 255 and in xapic otherwise, so the proposed > patch requires IR configuration only if BIOS switched apic to x2apic > mode. > > The patch is against tip:x86/apic. Applied to tip:x86/apic, thanks Gleb! Ingo