From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756116AbZEUQ1p (ORCPT ); Thu, 21 May 2009 12:27:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754502AbZEUQ1g (ORCPT ); Thu, 21 May 2009 12:27:36 -0400 Received: from wa4ehsobe005.messaging.microsoft.com ([216.32.181.15]:34150 "EHLO WA4EHSOBE006.bigfish.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754483AbZEUQ1g convert rfc822-to-8bit (ORCPT ); Thu, 21 May 2009 12:27:36 -0400 X-BigFish: VPS-23(zz1432R98dR168aJ1805Mzz1202hzzz32i6bh6di43j61h) X-Spam-TCS-SCL: 0:0 X-FB-SS: 5, X-WSS-ID: 0KK05PL-01-4ZF-01 Date: Thu, 21 May 2009 18:26:38 +0200 From: Borislav Petkov To: "H. Peter Anvin" CC: akpm@linux-foundation.org, greg@kroah.com, mingo@elte.hu, norsk5@yahoo.com, tglx@linutronix.de, mchehab@redhat.com, aris@redhat.com, edt@aei.ca, linux-kernel@vger.kernel.org, Andreas Herrmann Subject: Re: [PATCH 01/22] x86: add methods for writing of an MSR on several CPUs Message-ID: <20090521162638.GA10824@aftab> References: <1242390153-24493-1-git-send-email-borislav.petkov@amd.com> <1242390153-24493-2-git-send-email-borislav.petkov@amd.com> <20090519172449.GB18874@aftab> <4A1392A9.9010609@zytor.com> <20090520144905.GA27991@aftab> <4A147891.5000906@zytor.com> <20090521140800.GA3462@aftab> <4A156361.2040507@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline In-Reply-To: <4A156361.2040507@zytor.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-OriginalArrivalTime: 21 May 2009 16:26:40.0319 (UTC) FILETIME=[EBA00CF0:01C9DA30] Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 21, 2009 at 07:21:21AM -0700, H. Peter Anvin wrote: > Borislav Petkov wrote: > >>> > >> smp_call_function_many() does allow concurrent execution. > > > > Well, IMHO, not an absolutely concurrent execution since you can't > > control at what moment in time the IPIs will be executed on each core, > > IOW, the respective call function IPIs will generally not coincide on > > each core at a given moment in time. This is especially true if you're > > sending IPIs to cores across nodes. > > > > And there's hypothetically a small window where you might get an > > inconsistent MSR content across cores. It's a whole another question > > whether this is going to be relevant. > > > > It *allows* concurrent execution. It doesn't *guarantee* concurrent > execution. Exactly what I'm trying to say. > > So, the actual question is do we need that done in msr.c? If there are > > no potential users, I could easily do the whole thing in the driver and > > do not touch x86 code. > > Only if we care about the additional performance of having it be > nonserializing. Well, let's do the nonserializing thing and have it done right from the beginning. We might not care now but who knows..? -- Regards/Gruss, Boris. Operating | Advanced Micro Devices GmbH System | Karl-Hammerschmidt-Str. 34, 85609 Dornach b. München, Germany Research | Geschäftsführer: Thomas M. McCoy, Giuliano Meroni Center | Sitz: Dornach, Gemeinde Aschheim, Landkreis München (OSRC) | Registergericht München, HRB Nr. 43632