From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id 296D16B026A for ; Fri, 1 Jul 2016 12:14:15 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id e189so244504525pfa.2 for ; Fri, 01 Jul 2016 09:14:15 -0700 (PDT) Received: from blackbird.sr71.net ([2001:19d0:2:6:209:6bff:fe9a:902]) by mx.google.com with ESMTP id tp2si4810481pab.52.2016.07.01.09.14.14 for ; Fri, 01 Jul 2016 09:14:14 -0700 (PDT) Subject: Re: [PATCH 6/6] x86: Fix stray A/D bit setting into non-present PTEs References: <20160701001209.7DA24D1C@viggo.jf.intel.com> <20160701001218.3D316260@viggo.jf.intel.com> <5775F418.2000803@sr71.net> From: Dave Hansen Message-ID: <577696D5.2010609@sr71.net> Date: Fri, 1 Jul 2016 09:14:13 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Linux Kernel Mailing List , the arch/x86 maintainers , linux-mm , Andrew Morton , Borislav Petkov , Andi Kleen , Michal Hocko , Dave Hansen On 07/01/2016 09:07 AM, Linus Torvalds wrote: > But I also started worrying about us just losing sight of the dirty > bit in particular. It's not enough that we ignore the dirty bit - we'd > still want to make sure that the underlying backing page gets marked > dirty, even if the CPU is buggy and ends doing it "delayed" after > we've already unmapped the page. > > So I get this feeling that we may need a fair chunk of your > patch-series anyway. As I understand it, the erratum only affects a thread which is about to page fault. The write associated with the dirty bit being set never actually gets executed. So, the bit really *is* stray and isn't something we need to preserve. Otherwise, we'd be really screwed because we couldn't ever simply clear it. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org