Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH RFC 00/30] userfaultfd-wp: Support shmem and hugetlbfs
To:     Peter Xu <peterx@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Cc:     Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Jerome Glisse <jglisse@redhat.com>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Hugh Dickins <hughd@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Matthew Wilcox <willy@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Nadav Amit <nadav.amit@gmail.com>
References: <20210115170907.24498-1-peterx@redhat.com>
 <20210129224938.GC260413@xz-x1>
From:   Mike Kravetz <mike.kravetz@oracle.com>
Message-ID: <339d27e8-9f34-3e80-2910-46f46d58e9a6@oracle.com>
Date:   Fri, 5 Feb 2021 13:53:34 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.1.1
In-Reply-To: <20210129224938.GC260413@xz-x1>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-MessageSentRepresentingType: 1
Received: from [192.168.2.112] (50.38.35.18) by MW2PR16CA0032.namprd16.prod.outlook.com (2603:10b6:907::45) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3825.17 via Frontend Transport; Fri, 5 Feb 2021 21:53:35 +0000
X-MS-PublicTrafficType: Email
X-MS-Office365-Filtering-Correlation-Id: 5c1acd7a-5c86-45e0-b6b3-08d8ca207d00
X-MS-TrafficTypeDiagnostic: MWHPR10MB1694:
X-Microsoft-Antispam-PRVS: <MWHPR10MB1694618315B4B16AF838C678E2B29@MWHPR10MB1694.namprd10.prod.outlook.com>
X-MS-Oob-TLC-OOBClassifiers: OLM:8273;
X-MS-Exchange-SenderADCheck: 1
X-Microsoft-Antispam: BCL:0;
X-Microsoft-Antispam-Message-Info: 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
X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:MWHPR10MB1389.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(366004)(396003)(136003)(39860400002)(346002)(376002)(4326008)(186003)(316002)(66556008)(31696002)(16576012)(66476007)(83380400001)(66946007)(16526019)(478600001)(6486002)(2906002)(44832011)(26005)(52116002)(7416002)(86362001)(8936002)(4744005)(8676002)(54906003)(36756003)(2616005)(5660300002)(31686004)(956004)(53546011)(45980500001)(43740500002);DIR:OUT;SFP:1101;
X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?dkhvRkYxOUdZanZVS3hjZVFxWCtjRndGRnFFWTlWOXAwaWJ4N1R0K0FRd2lp?=
 =?utf-8?B?ck1sY2JWYndJZGw1UkxIcWRvNmZrUTkzN0JxeHhZcFVBWCsvS2VwQVU3VkE1?=
 =?utf-8?B?ZHc0dnllVUpDSlhDUDFQMVNXd2ZwQ1hhSGkwRHlvV3BKaUw2S0hDSWZIZ3VF?=
 =?utf-8?B?eGRQQlRzY21zb3NRQnRLZFlWWDBmUysxbzliZG14ZWdUS2IraUh2WTdWeUVm?=
 =?utf-8?B?enI2cHVOakRTQ3RKc05CbTZ3VVlUblMxMlArYnpTaXcwRVMvRWVZaHBDei84?=
 =?utf-8?B?Z2hvSU5kMmQzZU5DT3VwSFY1cGVIREZ0djJnamMyOUZTZFFDdXdsUXhtRWNa?=
 =?utf-8?B?WDY2ekNTSFRxWEFiVlpuV2lrYmtmeGQ4a2ZoZURPU2ZTUE5Da3VQNWNMTksw?=
 =?utf-8?B?YVRaclZ1bC9xSlJsL0dOMzVoM09XR2lOeE51KzQzSjQzY1BWbHptODhBUVRr?=
 =?utf-8?B?eVQrNGxDMURMeE5JUlBVZHlNTW12bUVxYzJEOTNIbXVhVDAzYjVDUmdEM2Nm?=
 =?utf-8?B?aTlkdlpUMDZOeG83VzhnZnBBWU9yb1Z3Y0NPWm9BMGF0RGpVb2Z3bWZmU1hI?=
 =?utf-8?B?elV0QXY2NE54cWRZMVNsVXR5d2tYZzRRN0lITUs2cE1HeGtGakY4b3pCWklx?=
 =?utf-8?B?cnQ4bXBrcmJNSmhDYjVNUitrZ3ZtNFllVGZjeHVtU3phRTVnWWprMkExUEdZ?=
 =?utf-8?B?b1NIRGdwOGJpQm9IeTdRQjA5eVpESFpkMHh5a2tWYWdnWmdoWlIxYzFmM3dY?=
 =?utf-8?B?OHBxWXhXakRvZ0duZHoxeFlDVmJUVjFoYm96MjdMdVRvL2kxN2xubk9MaEJT?=
 =?utf-8?B?RkhlUHg3d0JibjZPWVhsQlZRY3pKYUhMdVR6NXFzQ2xKam1nZ2ZUdUlFRGUv?=
 =?utf-8?B?QXdkeFQrNWxIMi9reUU3R29XaU9OWERpVFRraDd4d09KTlRYN3FiWkkrbUVx?=
 =?utf-8?B?QTdCYWpiZk9Ud2VyT2oyM2J2SFlHNzJ1U1hpbUhSOGllclV4YTRUajlIeEYz?=
 =?utf-8?B?ZGlhZkRDQURJc2dPNGxwTitlOEJzNjVQdHB5NlNhRmdDMjNibm9YaUtPa0FB?=
 =?utf-8?B?Qk5VeG83UFpKWnViaEttMElpQ2VFSzNycDVUM2RMVjI3TDhuLzM0ZTYwWEVa?=
 =?utf-8?B?L2JQTzQyeUR3bUFLa05SZFBQNkQ2dzdhTVRkZ3B5bVpRamxuQVlWTzErcE15?=
 =?utf-8?B?UEw0dHB6c1dLYVdja3FETXRuMGRmTEtBbFlQZWZWbFlFQVozZlZsK25zUW5t?=
 =?utf-8?B?czhvRkJIRUZ1cVludXZQMi9lNGZ6eTUyT1ZsTDJ5WW5IMk1xYjV4bGxLT3ZN?=
 =?utf-8?B?MWZJS1VtSWdBbWJrN0RVYWFOSkdoZVFjZTlDY0x1aW5zdC80NGRVSU84Yit0?=
 =?utf-8?B?UWdmYmZpRk9QZzVpdmNVdFBpMi9LYkZIUk9uZkZqMWRHYlRNejNTcnZZQkcv?=
 =?utf-8?B?WmcvaFo1RGxrZ2F4TnA2OVRrd2pGeVYzaUZYcUhId0xTazhueVJnRU5CcTR4?=
 =?utf-8?B?dE1YenBtZjZsMXR5M1dUUkxtai96TDBLam9WMGVVQTJuOFF0a29LcStMaDVN?=
 =?utf-8?B?OE9TdGV4T3lzTXBCOHpOUkpSN2F5b2tvOTgwUEM3aEg2RHNrMTRNTms5VGVU?=
 =?utf-8?B?NVhiRkVNMlR4YW5Lemovd09SOUlLMWJOVmZIaXArTUNyRmdrRlFVOHJTSHFh?=
 =?utf-8?B?bVd5RjY2WEVUWDBsWUNsVVdTMitkb3paLzdRbXpmOVR5UXhySHdsQXNWS1l1?=
 =?utf-8?Q?3ZFUSasvnD0tzQPeesTTuoKlT87or18SygZ1hYc?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 5c1acd7a-5c86-45e0-b6b3-08d8ca207d00
X-MS-Exchange-CrossTenant-AuthSource: MWHPR10MB1389.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Feb 2021 21:53:36.0816
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: GErJtdwbwVGHlixwTo1PDRkZNlZxfhJkGliU/uvdk4vUD4Rgbaz0lnP7ENqG2MwIpJMTgz19QDLctPiqcSpP0w==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR10MB1694
X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9886 signatures=668683
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 adultscore=0 suspectscore=0
 spamscore=0 mlxscore=0 malwarescore=0 mlxlogscore=999 phishscore=0
 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000
 definitions=main-2102050134
X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9886 signatures=668683
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 bulkscore=0 adultscore=0
 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1015
 spamscore=0 lowpriorityscore=0 phishscore=0 mlxlogscore=999 mlxscore=0
 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2009150000 definitions=main-2102050134
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 1/29/21 2:49 PM, Peter Xu wrote:
> On Fri, Jan 15, 2021 at 12:08:37PM -0500, Peter Xu wrote:
>> This is a RFC series to support userfaultfd upon shmem and hugetlbfs.
...
> Huge & Mike,
> 
> Would any of you have comment/concerns on the high-level design of this series?
> 
> It would be great to know it, especially major objection, before move on to an
> non-rfc version.

My apologies for not looking at this sooner.  Even now, I have only taken
a very brief look at the hugetlbfs patches.

Coincidentally, I am working on the 'BUG' that soft dirty does not work for
hugetlbfs.  As you can imagine, there is some overlap in handling of wp ptes
set for soft dirty.  In addition, pmd sharing must be disabled for soft dirty
as here and in Axel's uffd minor fault code.

No objections to the overall approach based on my quick look.

I'll try to take a closer look at the areas where efforts overlap.
-- 
Mike Kravetz