From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=6Pj3=CY=lists.ozlabs.org=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@kernel.org>
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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID,
	DKIM_SIGNED,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 16EC7C433E2
	for <linuxppc-dev@archiver.kernel.org>; Tue, 15 Sep 2020 17:12:30 +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 25A18206C9
	for <linuxppc-dev@archiver.kernel.org>; Tue, 15 Sep 2020 17:12:28 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=fail reason="signature verification failed" (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="Su2Y/VZR"
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 25A18206C9
Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3])
	by lists.ozlabs.org (Postfix) with ESMTP id 4BrVCZ68fLzDqLg
	for <linuxppc-dev@archiver.kernel.org>; Wed, 16 Sep 2020 03:12:26 +1000 (AEST)
Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized)
 smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1;
 helo=mx0a-001b2d01.pphosted.com; envelope-from=gor@linux.ibm.com;
 receiver=<UNKNOWN>)
Authentication-Results: lists.ozlabs.org;
 dmarc=pass (p=none dis=none) header.from=linux.ibm.com
Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key;
 unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256
 header.s=pp1 header.b=Su2Y/VZR; dkim-atps=neutral
Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com
 [148.163.156.1])
 (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 4BrV9Q3bz7zDqLg
 for <linuxppc-dev@lists.ozlabs.org>; Wed, 16 Sep 2020 03:10:34 +1000 (AEST)
Received: from pps.filterd (m0098410.ppops.net [127.0.0.1])
 by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id
 08FH3pQx087775; Tue, 15 Sep 2020 13:09:38 -0400
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com;
 h=date : from : to : cc :
 subject : message-id : references : mime-version : content-type :
 in-reply-to; s=pp1; bh=0SwsWPJcQ8csUf8qT+IW5LyVsjYQaHYS00V7321t2GI=;
 b=Su2Y/VZR9MFPTTe76itJJTC2PYOcVxxTPkTe16Z+dWUBxWmBnEEOPxMSKSiuSbIusBSD
 +muGOMobMoG+nNfYDxtE3jDvPkZxmtfg9tZiFjWrJvJlVTkTOGG7kqPJICVPKSZ5sKqg
 1sgfp6wjddy3brhgYwS8mw+c051uWPXeODG2jP0bn4wv5m61YFrcNzu3+fiyCM6evgRY
 Jd+HFnGXgVXjnS8FVFh8m8RCd5qh08IOuyExBsRsnHUWAiOweYzGOvZYsdmjTYSKG4b1
 7CerArw50uSE/wBNAL9yn7+mPPISXo8u+0b5hhswnVHoGWtYQzWCrj50oixD4qakn4LN 4w== 
Received: from pps.reinject (localhost [127.0.0.1])
 by mx0a-001b2d01.pphosted.com with ESMTP id 33k1pdg5n5-1
 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT);
 Tue, 15 Sep 2020 13:09:38 -0400
Received: from m0098410.ppops.net (m0098410.ppops.net [127.0.0.1])
 by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 08FH49XR088681;
 Tue, 15 Sep 2020 13:09:37 -0400
Received: from ppma02fra.de.ibm.com (47.49.7a9f.ip4.static.sl-reverse.com
 [159.122.73.71])
 by mx0a-001b2d01.pphosted.com with ESMTP id 33k1pdg5ka-1
 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT);
 Tue, 15 Sep 2020 13:09:37 -0400
Received: from pps.filterd (ppma02fra.de.ibm.com [127.0.0.1])
 by ppma02fra.de.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 08FH8Lnb026534;
 Tue, 15 Sep 2020 17:09:34 GMT
Received: from b06avi18878370.portsmouth.uk.ibm.com
 (b06avi18878370.portsmouth.uk.ibm.com [9.149.26.194])
 by ppma02fra.de.ibm.com with ESMTP id 33gny820bs-1
 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT);
 Tue, 15 Sep 2020 17:09:34 +0000
Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com
 [9.149.105.232])
 by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP
 id 08FH9VVo28901714
 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK);
 Tue, 15 Sep 2020 17:09:31 GMT
Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1])
 by IMSVA (Postfix) with ESMTP id A3DF152054;
 Tue, 15 Sep 2020 17:09:31 +0000 (GMT)
Received: from localhost (unknown [9.145.80.96])
 by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id 1BD555204E;
 Tue, 15 Sep 2020 17:09:29 +0000 (GMT)
Date: Tue, 15 Sep 2020 19:09:27 +0200
From: Vasily Gorbik <gor@linux.ibm.com>
To: Andrew Morton <akpm@linux-foundation.org>, Jason Gunthorpe <jgg@ziepe.ca>, 
 John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH v2] mm/gup: fix gup_fast with dynamic page table folding
Message-ID: <your-ad-here.call-01600189767-ext-4442@work.hours>
References: <20200911200511.GC1221970@ziepe.ca>
 <patch.git-943f1e5dcff2.your-ad-here.call-01599856292-ext-8676@work.hours>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <patch.git-943f1e5dcff2.your-ad-here.call-01599856292-ext-8676@work.hours>
X-TM-AS-GCONF: 00
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235, 18.0.687
 definitions=2020-09-15_12:2020-09-15,
 2020-09-15 signatures=0
X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0
 malwarescore=0
 impostorscore=0 mlxscore=0 bulkscore=0 mlxlogscore=993 suspectscore=1
 clxscore=1015 lowpriorityscore=0 spamscore=0 phishscore=0
 priorityscore=1501 adultscore=0 classifier=spam adjust=0 reason=mlx
 scancount=1 engine=8.12.0-2006250000 definitions=main-2009150137
X-BeenThere: linuxppc-dev@lists.ozlabs.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>
Cc: Peter Zijlstra <peterz@infradead.org>,
 Dave Hansen <dave.hansen@linux.intel.com>, linux-mm <linux-mm@kvack.org>,
 Paul Mackerras <paulus@samba.org>, linux-sparc <sparclinux@vger.kernel.org>,
 Alexander Gordeev <agordeev@linux.ibm.com>,
 Claudio Imbrenda <imbrenda@linux.ibm.com>, Will Deacon <will@kernel.org>,
 linux-arch <linux-arch@vger.kernel.org>,
 linux-s390 <linux-s390@vger.kernel.org>, Richard Weinberger <richard@nod.at>,
 linux-x86 <x86@kernel.org>, Russell King <linux@armlinux.org.uk>,
 Christian Borntraeger <borntraeger@de.ibm.com>, Ingo Molnar <mingo@redhat.com>,
 Catalin Marinas <catalin.marinas@arm.com>,
 Andrey Ryabinin <aryabinin@virtuozzo.com>,
 Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
 Heiko Carstens <hca@linux.ibm.com>, Arnd Bergmann <arnd@arndb.de>,
 Jeff Dike <jdike@addtoit.com>, linux-um <linux-um@lists.infradead.org>,
 Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
 Thomas Gleixner <tglx@linutronix.de>,
 linux-arm <linux-arm-kernel@lists.infradead.org>,
 Dave Hansen <dave.hansen@intel.com>,
 linux-power <linuxppc-dev@lists.ozlabs.org>,
 LKML <linux-kernel@vger.kernel.org>,
 Linus Torvalds <torvalds@linux-foundation.org>,
 Mike Rapoport <rppt@kernel.org>
Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Sender: "Linuxppc-dev"
 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On Fri, Sep 11, 2020 at 10:36:43PM +0200, Vasily Gorbik wrote:
> Currently to make sure that every page table entry is read just once
> gup_fast walks perform READ_ONCE and pass pXd value down to the next
> gup_pXd_range function by value e.g.:
...snip...
> ---
> v2: added brackets &pgd -> &(pgd)
> 
>  arch/s390/include/asm/pgtable.h | 42 +++++++++++++++++++++++----------
>  include/linux/pgtable.h         | 10 ++++++++
>  mm/gup.c                        | 18 +++++++-------
>  3 files changed, 49 insertions(+), 21 deletions(-)

Andrew, any chance you would pick this up?

There is an Ack from Linus. And I haven't seen any objections from Jason or John.
This seems to be as safe for other architectures as possible.

@Jason and John
Any acks/nacks?

Thank you,
Vasily