Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262078AbVEEMc4 (ORCPT ); Thu, 5 May 2005 08:32:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262080AbVEEMc4 (ORCPT ); Thu, 5 May 2005 08:32:56 -0400 Received: from pollux.ds.pg.gda.pl ([153.19.208.7]:48649 "EHLO pollux.ds.pg.gda.pl") by vger.kernel.org with ESMTP id S262078AbVEEMcy (ORCPT ); Thu, 5 May 2005 08:32:54 -0400 Date: Thu, 5 May 2005 13:32:49 +0100 (BST) From: "Maciej W. Rozycki" To: Len Brown Cc: Venkatesh Pallipadi , Zwane Mwaikambo , Andrew Morton , Linus Torvalds , mingo@elte.hu, linux-kernel , "Shah, Rajesh" , John Stultz , Andi Kleen , Asit K Mallick Subject: RE: [RFC][PATCH] i386 x86-64 Eliminate Local APIC timer interrupt In-Reply-To: <1115266581.7644.52.camel@d845pe> Message-ID: References: <88056F38E9E48644A0F562A38C64FB60049EE972@scsmsx403.amr.corp.intel.com> <1115266581.7644.52.camel@d845pe> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1393 Lines: 28 On Thu, 5 May 2005, Len Brown wrote: > Re: SMP using i8259 > While Linux in ACPI mode allows "noapic" on SMP, it isn't recommended. > It is there for comparisons, debugging, and to work-around the odd > broken system. It is an exception configuration, and supporting it > should in no way impact the design for other 99.99% normal systems. > > Indeed, note that SMP systems using i8259 instead of IOAPIC > is explicity forbidden by MPS, and thus would probably fail > the compatibility test for your favorite high volume binary OS. I'm not quite sure if that's forbidden by MPS -- the mixed mode certainly is not as not all interrupt sources may necessarily be routed to one of I/O APICs, and "noapic" can probably be treated as a special case of the mixed mode. Regardless, there used to be systems in existence that wouldn't route IRQ 0 to an I/O APIC, so using that interrupt requires either the mixed mode or using the "through-i8259A" trick (which unfortunately does not work for a subset of affected systems as a result of manufacturers implementing the Intel-recommended glue logic at the output of the master i8259). Maciej - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/