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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 26B3AC2D0DB for ; Tue, 28 Jan 2020 17:49:30 +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 9FD0A20716 for ; Tue, 28 Jan 2020 17:49:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FD0A20716 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 486Yyv4X5XzDq9D for ; Wed, 29 Jan 2020 04:49:27 +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 486Ywd1vywzDqHk for ; Wed, 29 Jan 2020 04:47:19 +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 5C6C9328; Tue, 28 Jan 2020 09:47:16 -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 1F3B43F52E; Tue, 28 Jan 2020 09:47:11 -0800 (PST) Date: Tue, 28 Jan 2020 17:47:09 +0000 From: Catalin Marinas To: Qian Cai Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers Message-ID: <20200128174709.GK655507@arrakis.emea.arm.com> References: <1580174873-18117-1-git-send-email-anshuman.khandual@arm.com> <14882A91-17DE-4ABD-ABF2-08E7CCEDF660@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <14882A91-17DE-4ABD-ABF2-08E7CCEDF660@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 , Vlastimil Babka , x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Tetsuo Handa , linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, Kees Cook , Anshuman Khandual , Masahiro Yamada , Dan Williams , Mark Brown , "Kirill A . Shutemov" , Thomas Gleixner , Gerald Schaefer , Sri Krishna chowdary , Dave Hansen , Greg Kroah-Hartman , Ard Biesheuvel , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Paul Burton , Mike Rapoport , 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 Mon, Jan 27, 2020 at 09:11:53PM -0500, Qian Cai wrote: > On Jan 27, 2020, at 8:28 PM, Anshuman Khandual wrote: > > This adds tests which will validate architecture page table helpers and > > other accessors in their compliance with expected generic MM semantics. > > This will help various architectures in validating changes to existing > > page table helpers or addition of new ones. [...] > What’s the value of this block of new code? It only supports x86 and > arm64 which are supposed to be good now. Did those tests ever find any > regression or this is almost only useful for new architectures which > only happened once in a few years? 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. See for example this past discussion: https://lore.kernel.org/linux-mm/20190628102003.GA56463@arrakis.emea.arm.com/ These tests should act as the 'contract' between the generic mm code and the architecture port. Without clear semantics, some bugs may be a lot subtler than a boot failure. FTR, I fully support this patch (and I should get around to review it properly; thanks for the reminder ;)). -- Catalin