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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 00314C83004 for ; Tue, 28 Apr 2020 05:54:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA101206D9 for ; Tue, 28 Apr 2020 05:54:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726447AbgD1Fy2 (ORCPT ); Tue, 28 Apr 2020 01:54:28 -0400 Received: from foss.arm.com ([217.140.110.172]:46122 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726210AbgD1Fy1 (ORCPT ); Tue, 28 Apr 2020 01:54:27 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0CE5731B; Mon, 27 Apr 2020 22:54:27 -0700 (PDT) Received: from [10.163.70.197] (unknown [10.163.70.197]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EA1F83F73D; Mon, 27 Apr 2020 22:54:19 -0700 (PDT) Subject: Re: [mm/debug] fa6726c1e7: kernel_BUG_at_include/linux/mm.h To: Christophe Leroy , Qian Cai Cc: kernel test robot , Stephen Rothwell , Catalin Marinas , Ingo Molnar , Mike Rapoport , Vineet Gupta , Will Deacon , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , "Kirill A. Shutemov" , Paul Walmsley , Palmer Dabbelt , Andrew Morton , LKML , lkp@lists.01.org References: <096a07fc-4525-feb6-5658-40bcffbd0a58@arm.com> From: Anshuman Khandual Message-ID: <9e9091b9-6918-d0af-dd92-3bdc0e29a4d5@arm.com> Date: Tue, 28 Apr 2020 11:23:51 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/28/2020 10:54 AM, Christophe Leroy wrote: > > > Le 28/04/2020 à 04:51, Qian Cai a écrit : >> >> >>> On Apr 27, 2020, at 10:35 PM, Anshuman Khandual wrote: >>> >>> Letting CONFIG_DEBUG_VM_PGTABLE enabled via CONFIG_EXPERT for unsupported >>> platforms i.e without ARCH_HAS_DEBUG_VM_PGTABLE, was a conscious decision >>> meant to expand it's adaptability and coverage without requiring any code >>> (i.e Kconfig) change. The easier it is to enable the test on unsupported >>> platforms right now, more folks are likely to try it out thus increasing >>> it's probability to get fixed on those platforms. That is a valid enough >>> reason to have CONFIG_EXPERT based enablement method, IMHO. Also even with >>> CONFIG_EXPERT set, CONFIG_DEBUG_VM_PGTABLE does not get enabled by default >>> automatically. >> >> No, I am talking about PAE. There is a distinction between known broken that nobody cares (like arm32) and in-progress/unknown status (like s390). >> >> Also, it is not very nice to introduce regressions for robots when testing PAE because they always select CONFIG__EXPERT and CONFIG_DEBUG_VM. >> > > Having CONFIG_EXPERT and CONFIG_DEBUG_VM is not enough to get CONFIG_DEBUG_VM_PGTABLE set to yes. Not automatically, that is right. But it can be set if required. Seems like the testing robots can and will test with each and every config whether they are enabled by default or not. So if we really need to prevent all possible testing robot regressions, X86_PAE needs to be disabled completely. > > By default, CONFIG_DEBUG_VM_PGTABLE is set to no when ARCH_HAS_DEBUG_VM_PGTABLE is not set. That is true. There is a slight change in the rules, making it explicit yes only when both ARCH_HAS_DEBUG_VM_PGTABLE and DEBUG_VM are enabled. +config DEBUG_VM_PGTABLE + bool "Debug arch page table for semantics compliance" + depends on MMU + depends on !IA64 && !ARM + depends on ARCH_HAS_DEBUG_VM_PGTABLE || EXPERT + default y if ARCH_HAS_DEBUG_VM_PGTABLE && DEBUG_VM + help The default is really irrelevant as the config option can be set explicitly.