From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938028AbZAPWas (ORCPT ); Fri, 16 Jan 2009 17:30:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S937832AbZAPWaY (ORCPT ); Fri, 16 Jan 2009 17:30:24 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:47008 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937164AbZAPWaX (ORCPT ); Fri, 16 Jan 2009 17:30:23 -0500 Date: Fri, 16 Jan 2009 23:30:11 +0100 From: Ingo Molnar To: Mike Travis Cc: Rusty Russell , LKML Subject: Re: [PULL}: latest tip/cpus4096 changes Message-ID: <20090116223011.GB3899@elte.hu> References: <49704DF6.8040205@sgi.com> <20090116092540.GC4305@elte.hu> <4970C984.30202@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4970C984.30202@sgi.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 * Mike Travis wrote: > Hi Ingo, > > I did notice that the versions all came up the same, and that the checks > were very specific. I was trying to be as transparent and unintrusive > as possible. Since there's so few calls, I though this was a good > approach but apparently I was wrong. > > I like the idea of collapsing the array down to one and checking to see > if all apic's have the same version, but is this really the case? Must > all apics be the same? Could you please send a patch that doesnt change the code, only adds a 'boot APIC version' kind of variable as an apic_version __read_mostly variable and does a WARN_ONCE() if that mismatches? We can then stick that into -tip and see whether it triggers. The max array size is ~128K, right? So if the WARN_ONCE() does not trigger, we can just drop the array and use the central apic_version variable ... And even if it _does_ trigger, the version incompatibilities between APIC protocols are very rare. They only happen across wildly different CPU architectures like when going from very old external apics to integrated apics, or going from apics to x-apics. We wont see any mixing across those boundaries. Ingo