From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752316AbcGAQOR (ORCPT ); Fri, 1 Jul 2016 12:14:17 -0400 Received: from www.sr71.net ([198.145.64.142]:43993 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750702AbcGAQOO (ORCPT ); Fri, 1 Jul 2016 12:14:14 -0400 Subject: Re: [PATCH 6/6] x86: Fix stray A/D bit setting into non-present PTEs To: Linus Torvalds References: <20160701001209.7DA24D1C@viggo.jf.intel.com> <20160701001218.3D316260@viggo.jf.intel.com> <5775F418.2000803@sr71.net> Cc: Linux Kernel Mailing List , the arch/x86 maintainers , linux-mm , Andrew Morton , Borislav Petkov , Andi Kleen , Michal Hocko , Dave Hansen From: Dave Hansen Message-ID: <577696D5.2010609@sr71.net> Date: Fri, 1 Jul 2016 09:14:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.