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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 39AFAC2BA83 for ; Wed, 12 Feb 2020 17:56:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14D4520714 for ; Wed, 12 Feb 2020 17:56:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729055AbgBLR4I (ORCPT ); Wed, 12 Feb 2020 12:56:08 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:13856 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729027AbgBLR4F (ORCPT ); Wed, 12 Feb 2020 12:56:05 -0500 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 01CHomt0085586 for ; Wed, 12 Feb 2020 12:56:04 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2y1ubt4g9b-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 12 Feb 2020 12:56:04 -0500 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 12 Feb 2020 17:56:01 -0000 Received: from b06cxnps3075.portsmouth.uk.ibm.com (9.149.109.195) by e06smtp05.uk.ibm.com (192.168.101.135) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 12 Feb 2020 17:55:51 -0000 Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 01CHtoBV51576916 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 12 Feb 2020 17:55:50 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8E98CA4055; Wed, 12 Feb 2020 17:55:50 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5B2C5A4057; Wed, 12 Feb 2020 17:55:49 +0000 (GMT) Received: from thinkpad (unknown [9.152.96.168]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 12 Feb 2020 17:55:49 +0000 (GMT) Date: Wed, 12 Feb 2020 18:55:48 +0100 From: Gerald Schaefer To: Anshuman Khandual Cc: Catalin Marinas , linux-mm@kvack.org, Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Tetsuo Handa , Heiko Carstens , Michal Hocko , Dave Hansen , Paul Mackerras , sparclinux@vger.kernel.org, Thomas Gleixner , linux-s390@vger.kernel.org, Michael Ellerman , x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Jason Gunthorpe , linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Ingo Molnar , Kees Cook , Masahiro Yamada , Mark Brown , "Kirill A . Shutemov" , Dan Williams , Vlastimil Babka , Christophe Leroy , Sri Krishna chowdary , Ard Biesheuvel , Greg Kroah-Hartman , 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" Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers In-Reply-To: References: <1580174873-18117-1-git-send-email-anshuman.khandual@arm.com> <20200210153716.GB9283@E121110.arm.com> 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: 20021217-0020-0000-0000-000003A98A3E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20021217-0021-0000-0000-00002201718D Message-Id: <20200212185548.3274ec2e@thinkpad> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-12_08:2020-02-12,2020-02-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxscore=0 priorityscore=1501 phishscore=0 adultscore=0 spamscore=0 clxscore=1015 bulkscore=0 lowpriorityscore=0 impostorscore=0 mlxlogscore=999 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002120131 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 12 Feb 2020 15:12:54 +0530 Anshuman Khandual wrote: > >> +/* > >> + * On s390 platform, the lower 12 bits are used to identify given page table > >> + * entry type and for other arch specific requirements. But these bits might > >> + * affect the ability to clear entries with pxx_clear(). So while loading up > >> + * the entries skip all lower 12 bits in order to accommodate s390 platform. > >> + * It does not have affect any other platform. > >> + */ > >> +#define RANDOM_ORVALUE (0xfffffffffffff000UL) > > > > I'd suggest you generate this mask with something like > > GENMASK(BITS_PER_LONG, PAGE_SHIFT). > > IIRC the lower 12 bits constrains on s390 platform might not be really related > to it's PAGE_SHIFT which can be a variable, but instead just a constant number. > But can definitely use GENMASK or it's variants here. > > https://lkml.org/lkml/2019/9/5/862 PAGE_SHIFT would be fine, it is 12 on s390. However, in order to be more precise, we do not really need all 12 bits, only the last 4 bits. So, something like this would work: #define RANDOM_ORVALUE GENMASK(BITS_PER_LONG - 1, 4) The text in the comment could then also be changed from 12 to 4, and be a bit more specific on the fact that the impact on pxx_clear() results from the dynamic page table folding logic on s390: /* * On s390 platform, the lower 4 bits are used to identify given page table * entry type. But these bits might affect the ability to clear entries with * pxx_clear() because of how dynamic page table folding works on s390. So * while loading up the entries do not change the lower 4 bits. * It does not have affect any other platform. */