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 A73D1C43219 for ; Thu, 29 Sep 2022 18:40:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1D0F58D0002; Thu, 29 Sep 2022 14:40:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 180D58D0001; Thu, 29 Sep 2022 14:40:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 047E08D0002; Thu, 29 Sep 2022 14:40:41 -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 E93268D0001 for ; Thu, 29 Sep 2022 14:40:40 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 72A4C80495 for ; Thu, 29 Sep 2022 18:40:40 +0000 (UTC) X-FDA: 79965989040.07.F16A6A3 Received: from na01-obe.outbound.protection.outlook.com (mail-centralusazon11013012.outbound.protection.outlook.com [52.101.64.12]) by imf10.hostedemail.com (Postfix) with ESMTP id 026AFC000C for ; Thu, 29 Sep 2022 18:40:39 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=iK7uu1aQ/FIJpbhuv2Nl/dtOoA/vf1fpi2n9TmRQQ5R/HgQ1AYZGfqqHgvJyhxz1Hmn00H6V1slpxksq8bofa39mGP+L66MB++QHmromqxxvLzva861354mxmwTubS7xMKaftQOWpYGlMQe8pYhamRvUNtujyymNFOyTRXIwASi1t7KUzBH/6WW9bZn+vWXusKTMESFJEBiGxMrYhWCVz6OluGVpwV9YTRLZamDXCUXD9tjNcahsofXgGBnorDkPV/ILp5cD/V6pfK68lcKch5RpczZUN0IFiZOVUUMoO8X//saAIICFxGR9noLt32oCDqewMvP5qVekIqm1OQ9LLQ== 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=lD8oE+u64k78vjM/TOju7+2Rdwyk5rFW1bPyqA2iduY=; b=nqBOS53LIGA4DRuhTwSGgixIrx6Y3/HOrdWLgORnd8UK5j7LcFqaP3PcB2SLKgNgxJCor8lxRG8rBJQapQNaSd9ujDcL2QJbVnfbTVWz56MqI0TpW8lDLPPPt1MhwJAMOdQhiJAGrhShcQkTwydWJPlhmI60BD0FMxjYz1XNLf95CG5Y95MFpY9uHMfl7YJJBF+f4CgxpRy8zjI1h+TWZvAhTSpY023QpJvl2zEDfGiBlL5x+dKVBq34yxQNiogFy2soDWB5o3Bng3wSMkN2iM07P2vdxwtCyZ01mH9pjk61/DsOGesfK/q8cEdIz4PG/tz8b7Y/GU45UYMMcsmcAw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=vmware.com; dmarc=pass action=none header.from=vmware.com; dkim=pass header.d=vmware.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vmware.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=lD8oE+u64k78vjM/TOju7+2Rdwyk5rFW1bPyqA2iduY=; b=sbhgHeFsUrO7Dle2ebQ4FHiVdwKPq1Bq8K6kxlNWSAlrY61pWFx3EmtSYFtwaDlkZAIViDcmqPoO9IQ0Zr0QvfxNa96FjMOxgje1f+6m2MkSrtqVuimM+PKhYmG8aGjASGC/2RD8lIUVBnhD/e0xFoSI5yEnAUc+2r5MKrjsSB0= Received: from BY3PR05MB8531.namprd05.prod.outlook.com (2603:10b6:a03:3ce::6) by BYAPR05MB4582.namprd05.prod.outlook.com (2603:10b6:a02:f2::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5676.13; Thu, 29 Sep 2022 18:40:36 +0000 Received: from BY3PR05MB8531.namprd05.prod.outlook.com ([fe80::942c:7d1b:6b3d:85b6]) by BY3PR05MB8531.namprd05.prod.outlook.com ([fe80::942c:7d1b:6b3d:85b6%5]) with mapi id 15.20.5676.020; Thu, 29 Sep 2022 18:40:36 +0000 From: Nadav Amit To: Chih-En Lin CC: David Hildenbrand , Andrew Morton , Qi Zheng , Matthew Wilcox , Christophe Leroy , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Luis Chamberlain , Kees Cook , Iurii Zaikin , Vlastimil Babka , William Kucharski , "Kirill A . Shutemov" , Peter Xu , Suren Baghdasaryan , Arnd Bergmann , Tong Tiangen , Pasha Tatashin , Li kunyu , Anshuman Khandual , Minchan Kim , Yang Shi , Song Liu , Miaohe Lin , Thomas Gleixner , Sebastian Andrzej Siewior , Andy Lutomirski , Fenghua Yu , Dinglan Peng , Pedro Fonseca , Jim Huang , Huichun Feng Subject: Re: [RFC PATCH v2 9/9] mm: Introduce Copy-On-Write PTE table Thread-Topic: [RFC PATCH v2 9/9] mm: Introduce Copy-On-Write PTE table Thread-Index: AQHY0o4wEIMbrk5BdEK3BIHQI3SfK63zm3IAgAAVHoCAATBzgIABi4GAgAA/C4CAABIqAIAAAxgA Date: Thu, 29 Sep 2022 18:40:36 +0000 Message-ID: References: <20220927162957.270460-1-shiyn.lin@gmail.com> <20220927162957.270460-10-shiyn.lin@gmail.com> <3D21021E-490F-4FE0-9C75-BB3A46A66A26@vmware.com> <39c5ef18-1138-c879-2c6d-c013c79fa335@redhat.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3696.120.41.1.1) x-ms-publictraffictype: Email x-ms-traffictypediagnostic: BY3PR05MB8531:EE_|BYAPR05MB4582:EE_ x-ms-office365-filtering-correlation-id: 0c1337da-af4d-4de8-b01f-08daa24a19a5 x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; 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dkim=pass header.d=vmware.com header.s=selector2 header.b=sbhgHeFs; spf=pass (imf10.hostedemail.com: domain of namit@vmware.com designates 52.101.64.12 as permitted sender) smtp.mailfrom=namit@vmware.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); dmarc=pass (policy=quarantine) header.from=vmware.com X-Stat-Signature: uqry5wame6hdwf98ffks4kxu8b8fpipx X-Rspamd-Queue-Id: 026AFC000C X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1664476839-775731 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: On Sep 29, 2022, at 11:29 AM, Chih-En Lin wrote: > That case could be caught in copy_pte_range(): in case we'd have to alloc= ate >> a page via page_copy_prealloc(), we'd have to fall back to the ordinary >> "separate page table for the child" way of doing things. >>=20 >> But that looks doable to me. >=20 > Sounds good. :) Chih-En, I admit I did not fully read the entire correspondence and got dee= p into all the details. I would note, however, that there are several additional components that I did not see (and perhaps missed) in your patches. Basically, there are many page-table manipulations that are done not through the page-fault handler o= r reclamation mechanisms. I did not see any of them being addressed. So if/when you send a new version, please have a look at mprotect(), madvise(), soft-dirty, userfaultfd and THP. In these cases, I presume, you would have to COW-break (aka COW-unshare) the page-tables.