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=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,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 666A0C43461 for ; Tue, 18 May 2021 19:45:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0DAE8610A2 for ; Tue, 18 May 2021 19:45:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0DAE8610A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8B3328E0041; Tue, 18 May 2021 15:45:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 88AC28E002F; Tue, 18 May 2021 15:45:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6DDFD8E0041; Tue, 18 May 2021 15:45:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0056.hostedemail.com [216.40.44.56]) by kanga.kvack.org (Postfix) with ESMTP id 3A82D8E002F for ; Tue, 18 May 2021 15:45:13 -0400 (EDT) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id D3082841B for ; Tue, 18 May 2021 19:45:12 +0000 (UTC) X-FDA: 78155380464.10.2DE2973 Received: from NAM04-DM6-obe.outbound.protection.outlook.com (mail-dm6nam08on2067.outbound.protection.outlook.com [40.107.102.67]) by imf11.hostedemail.com (Postfix) with ESMTP id 9CD11200025A for ; Tue, 18 May 2021 19:45:09 +0000 (UTC) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=fKQTzvvq0Jr42AObikhwhwbSltkrsz8l6q8RZsZZIANOXlFv76dZK+FfFGYFf+vFA1WyRW0DUXHQpklG4GN4hfpEQSjsAHeya/ngxfYNy9DF4WPnHlTCMML/x+X8Qoddybk+hLkSw0zXvJQRwtMZG6gkOrYu/Q8eBvAgjE7cBiMHVcevasBNVPV4+COm2T58Qyk+xeWPOKPiN8LbXwJ3wJ7JTPD4UOJzjSEi//fvF4CNVircUi6NgFULYUGxP5YPXPw7AIPfP0HGvzBXkRLEC1rgFk2IHhS48ibKz7+4S3Zhe9Fk/0gzNcTH/2AMLlv9ovQjcSBT97XW/mZGI+umAg== 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-SenderADCheck; bh=y05Y2Y1aMidJ5Ltn3J+VAAK8hHnG8kOEs8oVJwOVdCc=; b=VSd/NnQVf2GGjFiYmoT0J/Z/DOZ8AwDTfk2e+2NNI4MXzAZkDs5uCwTGo+PQB06VY2EadE1LPYAgcC/amG3bH6owXfCps/lAlpU/OkoJX2GrkbPb2LpvZDc95BtlBzKoN59RO7HLZ1Sd9+bpaH4d7clKeez3rz2FGHjMcxH3IJLrwba0ggxqPnTqGTvTzaqrBCIm+4uonhtpgXTLMfpxO6/93RE7aBrdOAATNDYNI/d2ia1USRgLBxAyDXCg45J4seMSzX/8TwMbQcqLjBm0DwANJqHA6FcAQ4BFLh37x5MxZ8k15qC/P0yhHwYSbsgA98+9BLCoGx853AylBjUK9w== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=y05Y2Y1aMidJ5Ltn3J+VAAK8hHnG8kOEs8oVJwOVdCc=; b=jhvgOTmcQJlfUPi3rY+h0kodsvjUxx0UsU6gjmo/zVw2xd5uX56ZczITiNJeMzmpWXn3hVuHrCuHyRHTRUCLFUBchE371nDTGX5cXHOB0pEgKRgjLZYi464hhLjHvM01+iAHBrdecluZH6nIrkyuj2DE0xgIeUo27BXD3dpyZNA9LTg7RJ+XumvdvywJUJnkXDZ2VdsZGvydr8D9KykN5A5ENS4p4tOiyI+QxFPrRHP49L+9O348P2b4nVkCLVsYiukIefNT2kJeDFKRhOX6MML4CKUEjEzYlmA3u8PQHAcUD9deFfXx4HGJQ/ME1yydHWTdEyJY+tbyaM01bG7XmA== Received: from DM6PR12MB3834.namprd12.prod.outlook.com (2603:10b6:5:14a::12) by DM6PR12MB3212.namprd12.prod.outlook.com (2603:10b6:5:186::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4129.28; Tue, 18 May 2021 19:45:10 +0000 Received: from DM6PR12MB3834.namprd12.prod.outlook.com ([fe80::ddb4:2cbb:4589:f039]) by DM6PR12MB3834.namprd12.prod.outlook.com ([fe80::ddb4:2cbb:4589:f039%4]) with mapi id 15.20.4129.031; Tue, 18 May 2021 19:45:10 +0000 Date: Tue, 18 May 2021 16:45:09 -0300 From: Jason Gunthorpe To: Peter Xu Cc: Alistair Popple , linux-mm@kvack.org, nouveau@lists.freedesktop.org, bskeggs@redhat.com, akpm@linux-foundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, jhubbard@nvidia.com, rcampbell@nvidia.com, jglisse@redhat.com, hch@infradead.org, daniel@ffwll.ch, willy@infradead.org, bsingharora@gmail.com, Christoph Hellwig Subject: Re: [PATCH v8 5/8] mm: Device exclusive memory access Message-ID: <20210518194509.GF1002214@nvidia.com> References: <20210407084238.20443-1-apopple@nvidia.com> <20210407084238.20443-6-apopple@nvidia.com> <47694715.suB6H4Uo8R@nvdebian> <20210518173334.GE1002214@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Originating-IP: [47.55.113.94] X-ClientProxiedBy: BL0PR03CA0018.namprd03.prod.outlook.com (2603:10b6:208:2d::31) To DM6PR12MB3834.namprd12.prod.outlook.com (2603:10b6:5:14a::12) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (47.55.113.94) by BL0PR03CA0018.namprd03.prod.outlook.com (2603:10b6:208:2d::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4129.25 via Frontend Transport; Tue, 18 May 2021 19:45:10 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1lj5eP-00AQvg-Cm; Tue, 18 May 2021 16:45:09 -0300 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 405f46c4-5a36-4831-4ba2-08d91a35727c X-MS-TrafficTypeDiagnostic: DM6PR12MB3212: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:6790; 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:DM6PR12MB3834.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(39860400002)(366004)(346002)(396003)(136003)(376002)(5660300002)(86362001)(426003)(2616005)(4326008)(4744005)(33656002)(38100700002)(1076003)(186003)(8676002)(9786002)(8936002)(9746002)(66476007)(66946007)(316002)(54906003)(2906002)(478600001)(7416002)(66556008)(36756003)(6916009)(26005);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: 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 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 405f46c4-5a36-4831-4ba2-08d91a35727c X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB3834.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 May 2021 19:45:10.8541 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: PlKj/0ol5HPuVdPinr9uw+4RrA+jlPJ/GU4TYo/OSuWrUqTK53QZM9mP5Ceahvqz X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB3212 X-Rspamd-Queue-Id: 9CD11200025A Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=jhvgOTmc; spf=none (imf11.hostedemail.com: domain of jgg@nvidia.com has no SPF policy when checking 40.107.102.67) smtp.mailfrom=jgg@nvidia.com; dmarc=pass (policy=none) header.from=nvidia.com X-Rspamd-Server: rspam04 X-Stat-Signature: 1mxgttg53edkfdehw7r77obrfwg9nymq X-HE-Tag: 1621367109-608627 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 Tue, May 18, 2021 at 02:01:36PM -0400, Peter Xu wrote: > > > Indeed it'll be odd for a COW page since for COW page then it means after > > > parent/child writting to the page it'll clone into two, then it's a mistery on > > > which one will be the one that "exclusived owned" by the device.. > > > > For COW pages it is like every other fork case.. We can't reliably > > write-protect the device_exclusive page during fork so we must copy it > > at fork time. > > > > Thus three reasonable choices: > > - Copy to a new CPU page > > - Migrate back to a CPU page and write protect it > > - Copy to a new device exclusive page > > IMHO the ownership question would really help us to answer this one.. I'm confused about what device ownership you are talking about It is just a page and it is tied to some specific pgmap? If the thing providing the migration stuff goes away then all device_exclusive pages should revert back to CPU pages and destroy the pgmap? Jason