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_1 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 56C0FC4BA24 for ; Thu, 27 Feb 2020 09:49:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 296BC24672 for ; Thu, 27 Feb 2020 09:49:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728704AbgB0Jt5 (ORCPT ); Thu, 27 Feb 2020 04:49:57 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:4240 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728632AbgB0Jt5 (ORCPT ); Thu, 27 Feb 2020 04:49:57 -0500 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 01R9igYs046184 for ; Thu, 27 Feb 2020 04:49:56 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ydq6x876r-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 27 Feb 2020 04:49:56 -0500 Received: from localhost by e06smtp05.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) Thu, 27 Feb 2020 09:49:51 -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 01R9nnXP61276208 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 27 Feb 2020 09:49:49 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B66A8A404D; Thu, 27 Feb 2020 09:49:49 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 74033A4057; Thu, 27 Feb 2020 09:49:49 +0000 (GMT) Received: from oc7455500831.ibm.com (unknown [9.152.224.219]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 27 Feb 2020 09:49:49 +0000 (GMT) Subject: Re: linux-next: manual merge of the akpm-current tree with the kvms390 tree To: David Hildenbrand , John Hubbard , Stephen Rothwell , Andrew Morton , Janosch Frank Cc: Linux Next Mailing List , Linux Kernel Mailing List , Claudio Imbrenda References: <20200227141148.05d7d502@canb.auug.org.au> <1217420e-42e4-9179-883f-125cf278caec@nvidia.com> From: Christian Borntraeger Autocrypt: addr=borntraeger@de.ibm.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20022709-0020-0000-0000-000003AE0C72 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20022709-0021-0000-0000-000022062AF5 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.572 definitions=2020-02-27_02:2020-02-26,2020-02-27 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 priorityscore=1501 malwarescore=0 lowpriorityscore=0 spamscore=0 mlxlogscore=999 clxscore=1015 mlxscore=0 adultscore=0 impostorscore=0 phishscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2002270078 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27.02.20 10:20, David Hildenbrand wrote: >> Yes. Changes to mm/gup.c really should normally go through linux-mm and >> Andrew's tree, if at all possible. This would have been caught, and figured out >> on linux-mm, had that been done--instead of leaving the linux-next maintainer >> trying to guess at how to resolve the conflict. >> >> +Cc David Hildenbrand, who I see looked at the kvms390 proposed patch a bit. >> Maybe he has some opinions, especially about my questions below. > > I'll leave figuring out the details to Christian/Claudio (-EBUSY) :) > >> >> The fix-up below may (or may not) need some changes: >> >> >> diff --cc mm/gup.c >> index 354bcfbd844b,f589299b0d4a..000000000000 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@@ -269,18 -470,11 +468,19 @@@ retry >> goto retry; >> } >> >> + /* try_grab_page() does nothing unless FOLL_GET or FOLL_PIN is set. */ >> + if (unlikely(!try_grab_page(page, flags))) { >> + page = ERR_PTR(-ENOMEM); >> + goto out; >> + } >> + if (flags & FOLL_GET) { >> >> >> If I'm reading the diff correctly, I believe that line should *maybe* be changed to: >> >> if (flags & (FOLL_GET | FOLL_PIN)) { >> >> ...because each of those flags has a similar effect: pinned pages for DMA or RDMA >> use. So either flag will require a call to arch_make_page_accessible()...except that >> I'm not sure that's what you want. Would the absence of a call to >> arch_make_page_accessible() cause things like pin_user_pages() to not work correctly? >> Seems like it would, to me. > > Yes, it's required. From the commit message "enable paging, file backing > etc, it is also necessary to protect the host against a malicious user > space. For example a bad QEMU could simply start direct I/O on such > protected memory.". So we really want to convert the page from > unencrypted/inaccessible to encrypted/accessible at this point (iow, > make it definitely accessible, and make sure it stays accessible). > >> >> (I'm pretty unhappy that we have to ask this at the linux-next level.) > > Yeah, I *think* this fell through the cracks (on linux-mm, but also in > Andrew's inbox) because the series has a big fat "KVM: s390:" as prefix. > Christian decided to pull it in to give it some churn yesterday (I think > he originally wanted to have this patch and the other KVM protvirt > patches in 5.7 [2] ... but not sure what will happen due to this conflict). Yes, I would like to have this patch in 5.7. Depending on the schedule of the FOLL_PIN patches that means: 1. Claudios callback patch _before_ the FOLL_PIN patches + Claudio will provide a fixup. 2. Claudios callback patch on top of the FOLL_PIN patches (Claudio will provide a version that combines the first patch + fixup) > > At least now this patch has attention ... although it would have been > better if linux-next admins wouldn't have to mess with this :) > > [1] https://lkml.kernel.org/r/20200224114107.4646-2-borntraeger@de.ibm.com > [2] https://lkml.kernel.org/r/20200224114107.4646-1-borntraeger@de.ibm.com >