Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 28 Feb 2001 18:05:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 28 Feb 2001 18:05:06 -0500 Received: from gateway.sequent.com ([192.148.1.10]:29330 "EHLO gateway.sequent.com") by vger.kernel.org with ESMTP id ; Wed, 28 Feb 2001 18:04:54 -0500 Date: Wed, 28 Feb 2001 15:04:44 -0800 From: "Martin J. Bligh" Reply-To: "Martin J. Bligh" To: linux-kernel@vger.kernel.org Subject: Re: Confused by local APIC addressing in setup_IO_APIC_irqs() Message-ID: <4120141070.983372684@W-MBLIG.svc.sequent.com> In-Reply-To: <4104841651.983357385@W-MBLIG.svc.sequent.com> X-Mailer: Mulberry/2.0.1 (Win32) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > But cpu_online map seems to be a 32 bit bitmask of which > CPUs are online .... are we stuffing this directly into an 8-bit > logical desitination register? > > Ironically, if I'm understanding this right, it kind of works anyway > for most systems - the low nibble of the logical ID is a bitmask > anyway, so it works normally for up to 4 way. For 8 way or more, > the high nibble will be set to 1111, which is the broadcast cluster ID, > so it'll direct interrupts anywhere .... but I can't believe that was > intentional ;-) For a start, a 7 way system would send to some > non-existant cluster ID .... Damn ... sorry - figured this out. The way Linux is doing it will work up to 8 CPUs. I'd forgotten that earlier on in my changes I'd switched the CPUs local APICs from FLAT logical addressing mode to CLUSTERED logical addressing mode. I need to switch the IO APIC code to match ... Thanks, Martin. - 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/