From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934439AbXGUWKL (ORCPT ); Sat, 21 Jul 2007 18:10:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762973AbXGUWJ7 (ORCPT ); Sat, 21 Jul 2007 18:09:59 -0400 Received: from terminus.zytor.com ([198.137.202.10]:36193 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751527AbXGUWJ6 (ORCPT ); Sat, 21 Jul 2007 18:09:58 -0400 Message-ID: <46A28425.2010202@zytor.com> Date: Sat, 21 Jul 2007 15:09:41 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Muli Ben-Yehuda CC: Andi Kleen , Glauber de Oliveira Costa , Linux Kernel Mailing List Subject: Re: [PATCH] x86: Create clflush() inline, remove hardcoded wbinvd References: <1184885740.16311.19.camel@t60> <200707202119.l6KLJwcd004205@tazenda.hos.anvin.org> <20070721181137.GH4152@rhun.haifa.ibm.com> <46A263FA.70501@zytor.com> <20070721201634.GF1193@rhun.ibm.com> <46A26A2E.7070305@zytor.com> <20070721204458.GG1193@rhun.ibm.com> In-Reply-To: <20070721204458.GG1193@rhun.ibm.com> X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Muli Ben-Yehuda wrote: > > Ok, let's try again: > > You're changing this (pageattr.c) > > asm volatile("clflush (%0)" :: "r" (adr + i)); > > into this: > > asm volatile("clflush %0" : "+m" (*(char __force*)(adr + i))); > > The original one calls clflush with (adr + i), the new one with (*(adr > + i)). Are these calls equivalent? Yes, they are. The parentheses which are part of the old assembly string has the same effect as the asterisk operator in C. The difference between the two is that the latter form allows the C compiler to select the addressing mode, which allows the full range of addressing modes, whereas the former forces it to use a single register indirect. -hpa