From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765571AbYDZBNU (ORCPT ); Fri, 25 Apr 2008 21:13:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755026AbYDZBNL (ORCPT ); Fri, 25 Apr 2008 21:13:11 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:52036 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753341AbYDZBNK (ORCPT ); Fri, 25 Apr 2008 21:13:10 -0400 Date: Fri, 25 Apr 2008 18:12:37 -0700 (PDT) From: Linus Torvalds To: "H. Peter Anvin" cc: Ingo Molnar , linux-kernel@vger.kernel.org, Andrew Morton , Thomas Gleixner Subject: Re: [git pull] x86 PAT changes In-Reply-To: <481271F4.7060401@zytor.com> Message-ID: References: <20080424225625.GB8717@elte.hu> <481271F4.7060401@zytor.com> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 25 Apr 2008, H. Peter Anvin wrote: > > The problem is that that can create cached/uncached aliases, which can cause > some processors to lock up (especially AMD is known to have a lot of errata in > this area.) Umm.. I don't think you understand. Right now, NONPROMISC_DEVMEM doesn't just disable mmap() on /dev/mem, it disables totally regular reads and writes too. That seems pretty damn excessive. If it was just mmap(), I don't think it would matter much. I don't think we traditionally even supported mmap() on real RAM (because the page counting would get confused), and that actually got supported only thanks to VM changes that made it possible. But read/write has always been supported, and shouldn't cause any cached/uncached aliases! Linus