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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3EE39C0015E for ; Wed, 19 Jul 2023 00:05:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C1B7A280020; Tue, 18 Jul 2023 20:05:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BCB028D0012; Tue, 18 Jul 2023 20:05:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A44D4280020; Tue, 18 Jul 2023 20:05:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 91E4D8D0012 for ; Tue, 18 Jul 2023 20:05:40 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 5D80D80537 for ; Wed, 19 Jul 2023 00:05:40 +0000 (UTC) X-FDA: 81026417640.02.C8963E6 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by imf20.hostedemail.com (Postfix) with ESMTP id E2B851C0022 for ; Wed, 19 Jul 2023 00:05:35 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=jmcW0arZ; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf20.hostedemail.com: domain of vivek.kasireddy@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=vivek.kasireddy@intel.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1689725136; a=rsa-sha256; cv=pass; b=d8cnAAKBLk83oKqb2XhKJ+y8vtN7M+M61hriUlYYXYteaLGR12I0rL1acRmk7H/AnRTLFS ARcLAqgFObH1mMszVWfpb3dzR0HIyye/8IlPeSj/2GoKrLb7B/hUqn5ZtjCNQz65TkzEow hVI2OAO42eRJPmu9xrXcjlWpcC7/Bp8= ARC-Authentication-Results: i=2; imf20.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=jmcW0arZ; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf20.hostedemail.com: domain of vivek.kasireddy@intel.com designates 134.134.136.24 as permitted sender) smtp.mailfrom=vivek.kasireddy@intel.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689725136; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=fTz0iV0JSp6sTXxiGkazPHA4/WUWPi5ejBJEzhHv+P4=; b=m0gXNdkdKC4SQVXatSC3D2nOzCVqycpB/cfG2mrgaLQgymRl/Wtg0NQ4QIPkBRskMDI38H zn36j8xgb+jJhHtYkPQTcfjeqWrJLwSO3corpHBXcyf0Gbq3ph4wnDoysIf8xFxNHHKati IlKAHbvuYYKJNDd1+jAmabnjHah/kgA= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689725136; x=1721261136; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=fTz0iV0JSp6sTXxiGkazPHA4/WUWPi5ejBJEzhHv+P4=; b=jmcW0arZcCc1GtkFqHx8tAl0JhfANtLJgd8uV5vZsiM4t+Ekeu8VmdjC 1LG+RJchL7y5/00qfHrloE7Zze5WA/QhgXiGiw/Sfn6Ek0mJ7MMJFooTs hDXrKlHSYZPixa5FaEmWA6LuAlFB9+731IBP7FKz+bcgJw+um9UVDIAuB MaL4IByZpzU0QMFbvpE9VjnQZ0siI+JylMmw7Q8TLxU+8qPunfRtdDhUh UBi3g/NVAUiGYLXVu7xgEsYfyAOrrexbODf5tegb26elx4tcOMVYPmjiw MkU83/K4tmtPazz1EgIV/G6nc0Q/u9I9QwXl9wjtl9sAYvLayoedfkuvo w==; X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="368984987" X-IronPort-AV: E=Sophos;i="6.01,215,1684825200"; d="scan'208";a="368984987" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2023 17:05:34 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="717802412" X-IronPort-AV: E=Sophos;i="6.01,215,1684825200"; d="scan'208";a="717802412" Received: from fmsmsx603.amr.corp.intel.com ([10.18.126.83]) by orsmga007.jf.intel.com with ESMTP; 18 Jul 2023 17:05:33 -0700 Received: from fmsmsx611.amr.corp.intel.com (10.18.126.91) by fmsmsx603.amr.corp.intel.com (10.18.126.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Tue, 18 Jul 2023 17:05:32 -0700 Received: from fmsmsx610.amr.corp.intel.com (10.18.126.90) by fmsmsx611.amr.corp.intel.com (10.18.126.91) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Tue, 18 Jul 2023 17:05:32 -0700 Received: from fmsedg602.ED.cps.intel.com (10.1.192.136) by fmsmsx610.amr.corp.intel.com (10.18.126.90) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27 via Frontend Transport; Tue, 18 Jul 2023 17:05:32 -0700 Received: from NAM11-BN8-obe.outbound.protection.outlook.com (104.47.58.168) by edgegateway.intel.com (192.55.55.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.27; Tue, 18 Jul 2023 17:05:32 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=i5ougk41UVQPskv88AQGyGjsPi5pHDjlKXKl8ZCR0EwvLTolDm4kUMSumXLBg0dl3Ybk444gKJCB7Ww09sJxbpppJUuTSlbzvF9zRgV8Jg6sHmQ19/s9BQa0LMkyOf0YEZ1UYyu9P1erMJ8Zrz91cc9kwmG6t+USfdFcFzkwGV9qfF88OyZuycLIGAlQk9XKbMOOZeFTpSF9vJb/7NeSKtQL9iCyxmFj3AqUMiZT4bT//kRg/Kapzfu2ob5xnteqjjByS/JT15ztJkPim2U5p09le+V3Dksa44vfQRbq8/Rgje+ciEDBzytYvscx1r3Wb86pg+2noQ7WOK5M5Ztz9A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=fTz0iV0JSp6sTXxiGkazPHA4/WUWPi5ejBJEzhHv+P4=; b=RiDPsFGa1q2IWwfsO0DzR2v0cnGLHBbTq0Tjb3pQKQga6RjDpWr9dxiSHLpVBbvqdc2EVR1EAiMe70m8QYL95mLAHSTzQbuOgkeiOGz+txfI3+RyMbZparhzKxWpoMzE9muH8WB/bcA8Wy/KzeSgDVn8piGnzmKpY06WbYx7yUZoEplgW9q9/0+B3FlV7HYulhK33idoU++mDKv1a+O9aNj7FIAIljuEcAR+pQPAl5tJ/qcd46l8I8fjohkkSSupEwUGLMKrH6i6/YNm9KHg08nOaO6+Yl9+udsYR5q5z5eQwlNs/XrJOaQLNoIiFwHzoIg//34AKXcE895/39MW1A== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Received: from IA0PR11MB7185.namprd11.prod.outlook.com (2603:10b6:208:432::20) by PH7PR11MB7145.namprd11.prod.outlook.com (2603:10b6:510:1ec::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6588.31; Wed, 19 Jul 2023 00:05:30 +0000 Received: from IA0PR11MB7185.namprd11.prod.outlook.com ([fe80::468a:4b39:392b:d9a9]) by IA0PR11MB7185.namprd11.prod.outlook.com ([fe80::468a:4b39:392b:d9a9%5]) with mapi id 15.20.6588.031; Wed, 19 Jul 2023 00:05:29 +0000 From: "Kasireddy, Vivek" To: Jason Gunthorpe CC: "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , David Hildenbrand , Mike Kravetz , Hugh Dickins , Peter Xu , Gerd Hoffmann , "Kim, Dongwon" , "Chang, Junxiao" Subject: RE: [RFC v1 1/3] mm/mmu_notifier: Add a new notifier for mapping updates (new pages) Thread-Topic: [RFC v1 1/3] mm/mmu_notifier: Add a new notifier for mapping updates (new pages) Thread-Index: AQHZuVToVshy99YkkE2dGyNcPWpnjq+/qJQAgABz7eA= Date: Wed, 19 Jul 2023 00:05:29 +0000 Message-ID: References: <20230718082858.1570809-1-vivek.kasireddy@intel.com> <20230718082858.1570809-2-vivek.kasireddy@intel.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-publictraffictype: Email x-ms-traffictypediagnostic: IA0PR11MB7185:EE_|PH7PR11MB7145:EE_ x-ms-office365-filtering-correlation-id: f49df3ff-a831-41c2-4cb3-08db87ebdd0e x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 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:IA0PR11MB7185.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(366004)(396003)(376002)(346002)(39860400002)(136003)(451199021)(5660300002)(478600001)(66446008)(66556008)(66476007)(66946007)(54906003)(52536014)(64756008)(15650500001)(4326008)(316002)(6916009)(76116006)(8936002)(55016003)(2906002)(8676002)(41300700001)(71200400001)(26005)(9686003)(7696005)(107886003)(6506007)(38100700002)(33656002)(186003)(82960400001)(83380400001)(122000001)(38070700005)(86362001);DIR:OUT;SFP:1102; x-ms-exchange-antispam-messagedata-chunkcount: 1 x-ms-exchange-antispam-messagedata-0: =?us-ascii?Q?Ze2xOn2Yc3fQwLJuwCLJlZ+xLr53FmpU01oK/TmbygVYsnzIBxDin/sQBITg?= =?us-ascii?Q?62EKEDM8Ru1VDw4tW85mAH05u/sjzY8acN36K+T/9UzEPPOXI2jhugiV2eUN?= =?us-ascii?Q?uTQPhDme1p8/3PbGembI0bVFr2kWx1tVGhRHlqss6N4/xXyzO3H07am+0jh+?= =?us-ascii?Q?H2f4MeY/UCC3RzgVAvExFdbZYTQmSsvbmigHLaKpN7UkqbEI8WQIutRNEgzQ?= =?us-ascii?Q?lVudnhZdXRpfsFVDRHcztFwcVUM7SS148Uo4osexdz5/WWRttOs54LFJDmOu?= =?us-ascii?Q?xlzD8pH85nQ7UT+LvQSCGOj5FN6IYTXkhQnmvrYor9F7PMfBxi8WO01DiJ1V?= =?us-ascii?Q?KCCJlHKLkipd3YsgrdJrfmxhDaxhHsmYJYdip2bWhF7ecuXOfxDIizhgyqOw?= =?us-ascii?Q?2eDdrsl8X/i8bVWJ3iZEKxqjZENL9QrrJeS2U2n56BCWgURsgfVyEN4DbAu2?= =?us-ascii?Q?9AqNDDFDbclULA7zoDW7/ZiAQZkxhMH1p6nW//ymnHiPzo0ka/+Qw92nwACI?= =?us-ascii?Q?2wlqi5oevw/JCrBr0sqTxd0J7iORMwzqkFHIoVUlaOEZNtj4iWxuAaOPCVMF?= =?us-ascii?Q?bK35ycLVPb86zA8DT4jZACcUHqn/rhOVl+6fR4ZnLTE0YSVfta6UWPPZNF80?= =?us-ascii?Q?kQEQ8vWH0RwX8oIZdUYU3kzN07m9+uAHCIp6ggI+BLeC6ABoQrsvGa+LpOt7?= =?us-ascii?Q?e3MBJdjGO2pzXt3XRw0O+AAwb/FcM+Kl1qzEw28MaOP22tvKSnEolkoaAY1S?= =?us-ascii?Q?5lIL0Edqa8MmTn6+S/Dwe0huXSCl09H7ZXqBajC8zMvIhw1KtzNJFSMNXRzw?= =?us-ascii?Q?n1jm00aMteUq/1T1t+gY7unemH7cXdwYbpuL46wxQOlbdRClXcOX4ZVL6bk3?= =?us-ascii?Q?Q3Q948LAjnuLhhwIzOlWSUkDC8k+/GBMeNyhqxulsEKvpP2KuSUacb8UptmD?= =?us-ascii?Q?/QKxGVjwBqG2aHTk3djyCjJkmvIFFiHvRlafpMaX9tAwK0OkVa7ZQqsJTt3r?= =?us-ascii?Q?XVxzprzRiSpvUE8pNClAe1RtuCiWiNwkHlImmmmqmfXeQzbETQzAxLDU5vq7?= =?us-ascii?Q?Sc0Mh8KYx7PP1Q49euq6wl2l/xhAkpI/Jc90wmD5MHbWYMmSiph7Y2T6XStI?= =?us-ascii?Q?aWhYSDP6I3P7xad8C2SNGwzRJKyIaoPhlLnbzhyyWV5o2FNILblwl78WE2zw?= =?us-ascii?Q?yMq74H3ktvLSBikPwL7weDfrqMmJf8FQq3xyV5Yt4SbHec+hvECeTDxv+QnF?= =?us-ascii?Q?oplAl6EfY+jStYJsIE+MFPvEjXvVr/eHo3vDoH9ymM6C3ddKMl5/YVGclBXk?= =?us-ascii?Q?suxMtkb7MGdEAxu27Tx6ls6sY2cE/Se5jQWz+FfrfEotlzOwNSLeRVHMPgGl?= =?us-ascii?Q?WYkJPUSNnebKIZIFG+JgkmsZtLr/FMVolFLlyfm8+pdAgSwRACvK70drx3wj?= =?us-ascii?Q?7hEe/SqJTP7Mudypz/2qGBr59SPBjWo7F1ylwQ69snWlE5fRYdpMAm/aEvWn?= =?us-ascii?Q?CRRxNDykkwB07DEVQf0ndAmho5rVAp4otGsPKT0HSR8Dbj1zgc2uNnxbG7xt?= =?us-ascii?Q?EuS+b/jnUazE+VMgieJoZWYZqkuJ0r4oM/p4QXem?= Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: IA0PR11MB7185.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: f49df3ff-a831-41c2-4cb3-08db87ebdd0e X-MS-Exchange-CrossTenant-originalarrivaltime: 19 Jul 2023 00:05:29.8304 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 7m3PWHLgQRt332vB4iGoyhzZDR1JBf/4Fpt+pacGAjV9sFzHvUGZdbU1cxdopeLTkeNXMxj+NcESWB1RPmVYdpstJ/tFX+UbXikdKhX3aJA= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR11MB7145 X-OriginatorOrg: intel.com X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E2B851C0022 X-Stat-Signature: mosk9nhqr3961c6xjxh3mq7a3heoha94 X-HE-Tag: 1689725135-158923 X-HE-Meta: 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 kyNJhCnY onu/RioJ+jAlgdknDODPUtNB1iez4ffPGyAhn7ZJYjRdzJg0n+MiqiuJmRTIXdvPFuCi0VmD2qVIUsuv86GVibCLcGWH81W74IbYsr7VdHpAeBjcnOYhK6xqx7fyUyke+z0M3WOlukfYp3944+/s1akfNaltV7jYTxub2bLMI5QgKuiF1YqAqAVR4mQ4RZnIhen3nKfzNe6U+ZZGC1urlyxqZRQublM6/o5DUZdxQBw8oZG3HwFiKUiwxBUQe4h9fVzrvtDDhq0t1zN/wjcnaYT4kr5e6tFYegAumPfaPQMxun6nWE1VGREpMZafcZbNnoIztLAhOKMB6LH0co+vy4OxNFjJOoGaVSSSzdWbEITHkwSPgpSAd5VBakJGOIu2uNfUl X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Jason, >=20 > On Tue, Jul 18, 2023 at 01:28:56AM -0700, Vivek Kasireddy wrote: > > Currently, there does not appear to be any mechanism for letting > > drivers or other kernel entities know about updates made in a > > mapping particularly when a new page is faulted in. Providing > > notifications for such situations is really useful when using > > memfds backed by ram-based filesystems such as shmem or hugetlbfs > > that also allow FALLOC_FL_PUNCH_HOLE. >=20 > Huh? You get an invalidate when this happens and the address becomes > non-present. Yes, we do get an invalidate (range) but it is not going to help given my use-case. This is because the invalidate only indicates that the old pages are gone (and not about the availability of new pages). IIUC, after a hole gets punched, it appears the new pages are faulted in only when there are writes made to that region where the hole was punched. So, I think what would really help is to get notified when a new page becomes part of the mapping at a given offset.=20 >=20 > > More specifically, when a hole is punched in a memfd (that is > > backed by shmem or hugetlbfs), a driver can register for > > notifications associated with range invalidations. However, it > > would also be useful to have notifications when new pages are > > faulted in as a result of writes made to the mapping region that > > overlaps with a previously punched hole. >=20 > If there is no change to the PTEs then it is hard to see why this > would be part of a mmu_notifier. IIUC, the PTEs do get changed but only when a new page is faulted in. For shmem, it looks like the PTEs are updated in handle_pte_fault() after shmem_fault() gets called and for hugetlbfs, this seems to happen in hugetlb_fault(). Instead of introducing a new notifier, I did think about reusing (or overloading) .change_pte() but I did not fully understand the impact it would have on KVM, the only user of .change_pte().=20 Thanks, Vivek >=20 > Jason