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_PASS,URIBL_BLOCKED autolearn=ham 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 C44ECC433F5 for ; Thu, 6 Sep 2018 09:59:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D5C4206BA for ; Thu, 6 Sep 2018 09:59:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D5C4206BA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728560AbeIFOdq (ORCPT ); Thu, 6 Sep 2018 10:33:46 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33394 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725809AbeIFOdp (ORCPT ); Thu, 6 Sep 2018 10:33:45 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w869wsiu007735 for ; Thu, 6 Sep 2018 05:59:04 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2mb1p3s0xq-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 06 Sep 2018 05:59:04 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 6 Sep 2018 10:59:02 +0100 Received: from b06cxnps3075.portsmouth.uk.ibm.com (9.149.109.195) by e06smtp02.uk.ibm.com (192.168.101.132) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 6 Sep 2018 10:58:59 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w869wwFn45219860 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 6 Sep 2018 09:58:58 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 27E6DAE051; Thu, 6 Sep 2018 12:58:20 +0100 (BST) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 34488AE045; Thu, 6 Sep 2018 12:58:18 +0100 (BST) Received: from skywalker (unknown [9.102.0.183]) by d06av26.portsmouth.uk.ibm.com (Postfix) with SMTP; Thu, 6 Sep 2018 12:58:17 +0100 (BST) Received: (nullmailer pid 6070 invoked by uid 1000); Thu, 06 Sep 2018 09:58:55 -0000 From: "Aneesh Kumar K.V" To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , npiggin@gmail.com, aneesh.kumar@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [RFC PATCH v1 00/17] ban the use of _PAGE_XXX flags outside platform specific code In-Reply-To: References: Date: Thu, 06 Sep 2018 15:28:55 +0530 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 x-cbid: 18090609-0008-0000-0000-0000026D2103 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18090609-0009-0000-0000-000021D54344 Message-Id: <8736uneylc.fsf@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-09-06_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=879 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1809060104 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christophe Leroy writes: > Today flags like for instance _PAGE_RW or _PAGE_USER are used through > common parts of code. > Using those directly in common parts of code have proven to lead to > mistakes or misbehaviour, because their use is not always as trivial > as one could think. > > For instance, (flags & _PAGE_USER) == 0 isn't enough to tell > that a page is a kernel page, because some targets are using > _PAGE_PRIVILEDGED and not _PAGE_USER, so the test has to be > (flags & (_PAGE_USER | _PAGE_PRIVILEDGED)) == _PAGE_PRIVILEDGED > This has to (bad) consequences: > > - All targets must define every bit, even the unsupported ones, > leading to a lot of useless #define _PAGE_XXX 0 > - If someone forgets to take into account all possible _PAGE_XXX bits > for the case, we can get unexpected behaviour on some targets. > > This becomes even more complex when we come to using _PAGE_RW. > Testing (flags & _PAGE_RW) is not enough to test whether a page > if writable or not, because: > > - Some targets have _PAGE_RO instead, which has to be unset to tell > a page is writable > - Some targets have _PAGE_R and _PAGE_W, in which case > _PAGE_RW = _PAGE_R | _PAGE_W > - Even knowing whether a page is readable is not always trivial because: > - Some targets requires to check that _PAGE_R is set to ensure page > is readable > - Some targets requires to check that _PAGE_NA is not set > - Some targets requires to check that _PAGE_RO or _PAGE_RW is set > > Etc .... > > In order to work around all those issues and minimise the risks of errors, > this serie aims at removing all use of _PAGE_XXX flags from powerpc code > and always use pte_xxx() and pte_mkxxx() accessors instead. Those accessors > are then defined in target specific parts of the kernel code. The series is really good. It also helps in code readability. Few things i am not sure there is a way to reduce the overhead - access = _PAGE_EXEC; + access = pte_val(pte_mkexec(__pte(0))); Considering we have multiple big endian to little endian coversion there for book3s 64. Other thing is __ioremap_at where we do + pte_t pte = __pte(flags); /* Make sure we have the base flags */ - if ((flags & _PAGE_PRESENT) == 0) + if (!pte_present(pte)) - err = map_kernel_page(v+i, p+i, flags); + err = map_kernel_page(v + i, p + i, pte_val(pte)); But otherwise for the series. Reviewed-by: Aneesh Kumar K.V