From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964867AbWDZU2o (ORCPT ); Wed, 26 Apr 2006 16:28:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964871AbWDZU2n (ORCPT ); Wed, 26 Apr 2006 16:28:43 -0400 Received: from smtp110.mail.mud.yahoo.com ([209.191.85.220]:44147 "HELO smtp110.mail.mud.yahoo.com") by vger.kernel.org with SMTP id S964867AbWDZU2m (ORCPT ); Wed, 26 Apr 2006 16:28:42 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=OHxHdjN+e8k0+GFykE9Zg9KGcHSrXsqwUwvJq1uOElCcU0yKlllbmUHmJbF72KFbdbIA3v8RugEI97FN6pAtKyc02y/AveBFfNJr0wAenNwb3lH26v8byDFIrWOCCfnShUKfS9wGPnnJeLO7nzPrnq9JoD3mMI4/Yx1X6O/aUFw= ; Message-ID: <444F9A8D.3040604@yahoo.com.au> Date: Thu, 27 Apr 2006 02:06:37 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Hugh Dickins CC: Keir Fraser , Jan Beulich , Zachary Amsden , linux-kernel@vger.kernel.org Subject: Re: [PATCH] i386: PAE entries must have their low word cleared first References: <444F95D8.76E4.0078.0@novell.com> <946b367619cfd3dcd3ba547e216e494b@cl.cam.ac.uk> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hugh Dickins wrote: > On Wed, 26 Apr 2006, Keir Fraser wrote: > >>We cannot use pte_clear() unless we redefine it for PAE. Currently it reduces >>to set_pte() which explicitly uses the wrong ordering (sets high *then* low, >>because it's normally used to introduce a mapping). > > > I overlooked that reversal completely. What a very good point. > I think that actually pte_clear() _does_ need to be redefined for PAE, > to reverse that ordering as you point out. Take a look at its use in > mm/highmem.c (where a comment states it's safe against speculative > execution, but a comment can't guarantee that!): what do you think? Speculative execution is safe I think (and so is ptep_get_and_clear_full, because in neither case will the virtual address be visible). Speculative prefetching + tlb instantiation, apparently no. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com