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_2 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 1887BC2D0DB for ; Wed, 29 Jan 2020 22:24:52 +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 BF9FE206F0 for ; Wed, 29 Jan 2020 22:24:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF9FE206F0 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=de.ibm.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 487J2B0HLJzDqVK for ; Thu, 30 Jan 2020 09:24:50 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=de.ibm.com (client-ip=148.163.158.5; helo=mx0a-001b2d01.pphosted.com; envelope-from=gerald.schaefer@de.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=de.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 487Hxq12knzDqT6 for ; Thu, 30 Jan 2020 09:21:02 +1100 (AEDT) Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 00TMJNo0065537 for ; Wed, 29 Jan 2020 17:21:00 -0500 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2xttnu5rdq-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 29 Jan 2020 17:21:00 -0500 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 29 Jan 2020 22:20:47 -0000 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06avi18626390.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 00TMJtGT43974988 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 29 Jan 2020 22:19:55 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E97D85204E; Wed, 29 Jan 2020 22:20:46 +0000 (GMT) Received: from thinkpad (unknown [9.152.96.253]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id BB14952052; Wed, 29 Jan 2020 22:20:45 +0000 (GMT) Date: Wed, 29 Jan 2020 23:20:44 +0100 From: Gerald Schaefer To: Qian Cai Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers In-Reply-To: <016A776F-EFD9-4D2B-A3A9-788008617D95@lca.pw> References: <1580174873-18117-1-git-send-email-anshuman.khandual@arm.com> <14882A91-17DE-4ABD-ABF2-08E7CCEDF660@lca.pw> <214c0d53-eb34-9b0c-2e4e-1aa005146331@arm.com> <016A776F-EFD9-4D2B-A3A9-788008617D95@lca.pw> X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20012922-0016-0000-0000-000002E1DF70 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20012922-0017-0000-0000-00003344A733 Message-Id: <20200129232044.2d133d98@thinkpad> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-01-29_07:2020-01-28, 2020-01-29 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 spamscore=0 impostorscore=0 phishscore=0 bulkscore=0 suspectscore=60 adultscore=0 priorityscore=1501 mlxlogscore=999 lowpriorityscore=0 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1911200001 definitions=main-2001290171 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 , Tetsuo Handa , Heiko Carstens , Michal Hocko , Linux-MM , Paul Mackerras , sparclinux@vger.kernel.org, Thomas Gleixner , linux-s390@vger.kernel.org, x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Jason Gunthorpe , linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, Ingo Molnar , Kees Cook , Anshuman Khandual , Masahiro Yamada , Mark Brown , "Kirill A . Shutemov" , Dan Williams , Vlastimil Babka , Sri Krishna chowdary , Ard Biesheuvel , Greg Kroah-Hartman , Dave Hansen , 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, 27 Jan 2020 22:33:08 -0500 Qian Cai wrote: > > > >> Did those tests ever find any regression or this is almost only useful for new > > > > The test has already found problems with s390 page table helpers. > > Hmm, that is pretty weak where s390 is not even official supported with this version. > I first had to get the three patches upstream, each fixing non-conform behavior on s390, and each issue was found by this extremely useful test: 2416cefc504b s390/mm: add mm_pxd_folded() checks to pxd_free() 2d1fc1eb9b54 s390/mm: simplify page table helpers for large entries 1c27a4bc817b s390/mm: make pmd/pud_bad() report large entries as bad I did not see any direct effect of this misbehavior yet, but I am very happy that this could be found and fixed in order to prevent future issues. And this is exactly the value of this test, to make sure that all architectures have a common understanding of how the various page table helpers are supposed to work. For example, who would have thought that pXd_bad() is supposed to report large entries as bad? It's not really documented anywhere, so we just checked them for sanity like normal entries, which apparently worked fine so far, but for how long?