From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932164AbVH3Oua (ORCPT ); Tue, 30 Aug 2005 10:50:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932159AbVH3Ou3 (ORCPT ); Tue, 30 Aug 2005 10:50:29 -0400 Received: from ns2.suse.de ([195.135.220.15]:24271 "EHLO mx2.suse.de") by vger.kernel.org with ESMTP id S932164AbVH3Ou2 (ORCPT ); Tue, 30 Aug 2005 10:50:28 -0400 From: Andi Kleen To: Alan Cox Subject: Re: [PATCH] i386, x86_64 Initial PAT implementation Date: Tue, 30 Aug 2005 16:50:22 +0200 User-Agent: KMail/1.8 Cc: "Eric W. Biederman" , Andrew Morton , linux-kernel@vger.kernel.org References: <1125413136.8276.14.camel@localhost.localdomain> In-Reply-To: <1125413136.8276.14.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200508301650.23149.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday 30 August 2005 16:45, Alan Cox wrote: > On Llu, 2005-08-29 at 18:20 -0600, Eric W. Biederman wrote: > > ways. Currently this code only allows for an additional flavor > > of uncached access to physical memory addresses which should be hard > > to abuse, and should raise no additional aliasing problems. No > > attempt has been made to fix theoretical aliasing problems. > > Even an uncached/cached alias causes random memory corruption or an MCE > on x86 systems. In fact it can occur even for an alias not in theory > touched by the CPU if it happens to prefetch into or speculate the > address. > > Also be sure to read the PII Xeon errata - early PAT has a bug or two. We can always force cpu_has_pat == 0 on these machines. I don't think it is worth it to add any more complicated workarounds for old broken systems. -Andi