From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757928AbXLHAVh (ORCPT ); Fri, 7 Dec 2007 19:21:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754443AbXLHAV1 (ORCPT ); Fri, 7 Dec 2007 19:21:27 -0500 Received: from one.firstfloor.org ([213.235.205.2]:38881 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753455AbXLHAV1 (ORCPT ); Fri, 7 Dec 2007 19:21:27 -0500 Date: Sat, 8 Dec 2007 01:21:22 +0100 From: Andi Kleen To: Pavel Machek Cc: "David P. Reed" , Andi Kleen , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops Message-ID: <20071208002122.GC5992@one.firstfloor.org> References: <475879CD.9080006@reed.com> <47595DB2.5080302@reed.com> <20071205111039.GA3864@ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071205111039.GA3864@ucw.cz> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 05, 2007 at 11:10:39AM +0000, Pavel Machek wrote: > On Fri 2007-12-07 09:50:26, David P. Reed wrote: > > My machine in question, for example, needs no waiting > > within CMOS_READs at all. And I doubt any other > > chip/device needs waiting that isn't already provided by > > the bus. the i/o to port 80 is very, very odd in this > > context. Actually, modern machines have potentially > > more serious problems with i/o ops to non-existent > > addresses, which may cause real bus wierdness. > > I dislike outb_p clobbering port 0x80, but you are wrong here. BIOSes > already do outs to port 0x80 for debugging reason, so these accesses > are unlikely to do something bad. They only do that briefly during boot though. But Linux can do it much more often. If it's a race or similar it might just not trigger with the BIOS. -Andi