From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763789AbXGVTzn (ORCPT ); Sun, 22 Jul 2007 15:55:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760593AbXGVTzf (ORCPT ); Sun, 22 Jul 2007 15:55:35 -0400 Received: from one.firstfloor.org ([213.235.205.2]:54344 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760203AbXGVTzf (ORCPT ); Sun, 22 Jul 2007 15:55:35 -0400 Date: Sun, 22 Jul 2007 21:55:32 +0200 From: Andi Kleen To: "H. Peter Anvin" Cc: Andi Kleen , Glauber de Oliveira Costa , Linux Kernel Mailing List Subject: Re: [PATCH] x86: Create clflush() inline, remove hardcoded wbinvd Message-ID: <20070722195532.GA1432@one.firstfloor.org> References: <1184885740.16311.19.camel@t60> <200707202119.l6KLJwcd004205@tazenda.hos.anvin.org> <20070720212741.GB565@one.firstfloor.org> <46A12A3A.4020305@zytor.com> <20070722091826.GA28313@one.firstfloor.org> <46A39C64.9070301@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <46A39C64.9070301@zytor.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 22, 2007 at 11:05:24AM -0700, H. Peter Anvin wrote: > Andi Kleen wrote: > >> The main reason is that everyone seems to invoke it either incorrectly > > Where is it incorrect? > > Using "r" or "m" (as opposed as "+m") gives gcc the wrong dependency > information, and it could, at least in theory, cause memory references > to be moved around it -- especially when using "r". That doesn't sound correct. Taking the address should be like an escaping pointer and equivalent to read/write and effectively disable optimizations on this memory. -Andi