Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759099AbYJ3VzT (ORCPT ); Thu, 30 Oct 2008 17:55:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753346AbYJ3VzE (ORCPT ); Thu, 30 Oct 2008 17:55:04 -0400 Received: from byss.tchmachines.com ([208.76.80.75]:54219 "EHLO byss.tchmachines.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753021AbYJ3VzD (ORCPT ); Thu, 30 Oct 2008 17:55:03 -0400 Date: Thu, 30 Oct 2008 14:54:56 -0700 From: Ravikiran G Thirumalai To: Arjan van de Ven Cc: Ingo Molnar , venkatesh.pallipadi@intel.com, linux-kernel@vger.kernel.org, tim@scalemp.com, shai@scalex86.org Subject: Re: [patch] x86: Fix /dev/mem mmap breakage when PAT is disabled Message-ID: <20081030215455.GC6583@localdomain> References: <20081030020203.GA12423@localdomain> <20081030132103.2daff1e1@infradead.org> <20081030212121.GB6583@localdomain> <20081030142949.75df90cc@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081030142949.75df90cc@infradead.org> User-Agent: Mutt/1.5.15+20070412 (2007-04-11) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - byss.tchmachines.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - scalex86.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1378 Lines: 35 On Thu, Oct 30, 2008 at 02:29:49PM -0700, Arjan van de Ven wrote: >On Thu, 30 Oct 2008 14:21:21 -0700 >Ravikiran G Thirumalai wrote: > >> On Thu, Oct 30, 2008 at 01:21:03PM -0700, Arjan van de Ven wrote: >> >On Wed, 29 Oct 2008 19:02:03 -0700 >> >Ravikiran G Thirumalai wrote: >> > >> >well... technically the aliases are bad without PAT as well... >> > >> >> Hmm! Well, you mean if mtrr is used to change attributes? > >you can also set uncached in the pagetables, like via ioremap_uncached >and other ways. > >and /dev/mem may or may not imply cached/uncached, depending on the >open flags. > >On memory... what would that mean? > Well, I am not denying that an incorrectly written userspace program could cause cache aliasing/crash the system I am not arguing for or against this argument at all. However, there is what seems like an unintended change in behavior from 2.6.25 to 2.6.26 when CONFIG_STRICT_DEVMEM is disabled and PAT is disabled, which is a bug, and this patch fixes it that's all. If this was intentional, then I don't see the reason for having CONFIG_STRICT_DEVMEM!! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/