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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 6A9E3C33CB2 for ; Wed, 29 Jan 2020 10:38:41 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CAFE72071E for ; Wed, 29 Jan 2020 10:38:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CAFE72071E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4870ML4sqgzDqSj for ; Wed, 29 Jan 2020 21:38:38 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=catalin.marinas@arm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=arm.com Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4870KJ6pFGzDqRh for ; Wed, 29 Jan 2020 21:36:50 +1100 (AEDT) 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 F35521FB; Wed, 29 Jan 2020 02:36:47 -0800 (PST) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.47]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B1FB23F52E; Wed, 29 Jan 2020 02:36:42 -0800 (PST) Date: Wed, 29 Jan 2020 10:36:40 +0000 From: Catalin Marinas To: Qian Cai Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers Message-ID: <20200129103640.GA668562@arrakis.emea.arm.com> References: <20200128174709.GK655507@arrakis.emea.arm.com> <69091BA4-18C4-4425-A5E2-31FBE4654AF9@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <69091BA4-18C4-4425-A5E2-31FBE4654AF9@lca.pw> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Heiko Carstens , Michal Hocko , linux-mm@kvack.org, Paul Mackerras , sparclinux@vger.kernel.org, Ingo Molnar , linux-s390@vger.kernel.org, Jason Gunthorpe , x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Tetsuo Handa , Vlastimil Babka , linux-snps-arc@lists.infradead.org, Kees Cook , Anshuman Khandual , Gerald Schaefer , Mark Brown , "Kirill A . Shutemov" , Dan Williams , linux-arm-kernel@lists.infradead.org, Sri Krishna chowdary , Masahiro Yamada , Greg Kroah-Hartman , Ard Biesheuvel , Dave Hansen , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Paul Burton , Mike Rapoport , Thomas Gleixner , Vineet Gupta , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, Jan 28, 2020 at 02:07:10PM -0500, Qian Cai wrote: > On Jan 28, 2020, at 12:47 PM, Catalin Marinas wrote: > > The primary goal here is not finding regressions but having clearly > > defined semantics of the page table accessors across architectures. x86 > > and arm64 are a good starting point and other architectures will be > > enabled as they are aligned to the same semantics. > > This still does not answer the fundamental question. If this test is > simply inefficient to find bugs, Who said this is inefficient (other than you)? > who wants to spend time to use it regularly? Arch maintainers, mm maintainers introducing new macros or assuming certain new semantics of the existing macros. > If this is just one off test that may get running once in a few years > (when introducing a new arch), how does it justify the ongoing cost to > maintain it? You are really missing the point. It's not only for a new arch but changes to existing arch code. And if the arch code churn in this area is relatively small, I'd expect a similarly small cost of maintaining this test. If you only turn DEBUG_VM on once every few years, don't generalise this to the rest of the kernel developers (as others pointed out, this test is default y if DEBUG_VM). Anyway, I think that's a pointless discussion, so not going to reply further (unless you have technical content to add). -- Catalin