From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A6D1C433F5 for ; Thu, 6 Sep 2018 18:09:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 65B9D2075B for ; Thu, 6 Sep 2018 18:09:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 65B9D2075B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730363AbeIFWpg (ORCPT ); Thu, 6 Sep 2018 18:45:36 -0400 Received: from mx2.suse.de ([195.135.220.15]:33536 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728354AbeIFWpf (ORCPT ); Thu, 6 Sep 2018 18:45:35 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 84669ACBB; Thu, 6 Sep 2018 18:08:56 +0000 (UTC) Date: Thu, 6 Sep 2018 20:08:54 +0200 From: Michal Hocko To: Dave Hansen Cc: Pasha Tatashin , Alexander Duyck , linux-mm , LKML , "Duyck, Alexander H" , Andrew Morton , Ingo Molnar , "Kirill A. Shutemov" Subject: Re: [PATCH v2 1/2] mm: Move page struct poisoning to CONFIG_DEBUG_VM_PAGE_INIT_POISON Message-ID: <20180906180854.GG14951@dhcp22.suse.cz> References: <20180905211041.3286.19083.stgit@localhost.localdomain> <20180905211328.3286.71674.stgit@localhost.localdomain> <20180906054735.GJ14951@dhcp22.suse.cz> <0c1c36f7-f45a-8fe9-dd52-0f60b42064a9@intel.com> <20180906151336.GD14951@dhcp22.suse.cz> <4f154937-118c-96cf-cf8e-c95a2ca68d44@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 06-09-18 10:07:51, Dave Hansen wrote: > On 09/06/2018 09:12 AM, Pasha Tatashin wrote: > > > > I do not want to make this feature less tested. Poisoning memory allowed > > us to catch corner case bugs like these: > > > > ab1e8d8960b68f54af42b6484b5950bd13a4054b > > mm: don't allow deferred pages with NEED_PER_CPU_KM > > > > e181ae0c5db9544de9c53239eb22bc012ce75033 > > mm: zero unavailable pages before memmap init > > > > And several more that were fixed by other people. > > Just curious: were these found in the wild, or by a developer doing > normal development having turned on lots of debug options? Some of those were 0day AFAIR but my memory is quite dim. Pavel will know better. The bottom line is, however, that those bugs depend on strange or unexpected memory configurations or HW which is usually deployed outside of developers machine pool. So more people have this enabled the more likely we hit all those strange corner cases nobody even thought of. -- Michal Hocko SUSE Labs