From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 19 Sep 2001 14:58:03 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 19 Sep 2001 14:57:53 -0400 Received: from zikova.cvut.cz ([147.32.235.100]:20997 "EHLO zikova.cvut.cz") by vger.kernel.org with ESMTP id ; Wed, 19 Sep 2001 14:57:46 -0400 From: "Petr Vandrovec" Organization: CC CTU Prague To: Dan Hollis Date: Wed, 19 Sep 2001 20:57:59 MET-1 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: Re[2]: [PATCH] Athlon bug stomper. Pls apply. CC: , torvalds@transmeta.com X-mailer: Pegasus Mail v3.40 Message-ID: <3ED700D6987@vcnet.vc.cvut.cz> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 19 Sep 01 at 11:43, Dan Hollis wrote: > On Wed, 19 Sep 2001, Linus Torvalds wrote: > > It is _probably_ an undocumented performance thing, and clearing that > > bit may slow something down. But it might also change some behaviour, > > and knowing _what_ the behaviour is might be very useful for figuring > > out what it is that triggers the problem. > > AFAIK noone has even tested it yet to see what it does to performance! Eg > it might slow down memory access so that athlon-optimized memcopy is now > slower than non-athlon-optimized memcopy. And if it turns out to be the > case, we might as well just use the non-athlon-optimized memcopy instead > of twiddling undocumented northbridge bits... No, we cannot. On boxes which do not work with athlon optimized kernels any user can execute athlon's fast_page_copy from userspace, causing corruption on completely unrelated pages, eventually leading to kernel crash... So you cannot allow untrusted users on such machine. Best regards, Petr Vandrovec vandrove@vc.cvut.cz