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Wed, 19 May 2021 12:46:49 +0000 Received: from nvdebian.localnet (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 19 May 2021 12:46:45 +0000 From: Alistair Popple To: Peter Xu CC: , , , , , , , , , , , , , , , Christoph Hellwig Subject: Re: [PATCH v8 5/8] mm: Device exclusive memory access Date: Wed, 19 May 2021 22:46:43 +1000 Message-ID: <5737557.YXifvZZQQ8@nvdebian> In-Reply-To: References: <20210407084238.20443-1-apopple@nvidia.com> <2217153.lfGrokb94b@nvdebian> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 4f4ab20d-e196-4841-2c75-08d91ac42b5c X-MS-TrafficTypeDiagnostic: MN2PR12MB3582: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:3276; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid03.nvidia.com;CAT:NONE;SFS:(4636009)(136003)(396003)(39860400002)(376002)(346002)(36840700001)(46966006)(9686003)(316002)(426003)(36906005)(8936002)(8676002)(54906003)(33716001)(26005)(356005)(478600001)(4744005)(16526019)(336012)(5660300002)(82740400003)(9576002)(7416002)(70206006)(83380400001)(36860700001)(86362001)(47076005)(82310400003)(6916009)(7636003)(4326008)(2906002)(70586007)(186003)(39026012);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 May 2021 12:46:49.1889 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4f4ab20d-e196-4841-2c75-08d91ac42b5c X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT063.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB3582 Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=f5pHp0x3; dmarc=pass (policy=none) header.from=nvidia.com; spf=none (imf19.hostedemail.com: domain of apopple@nvidia.com has no SPF policy when checking 40.107.223.42) smtp.mailfrom=apopple@nvidia.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6F8CE90009DE X-Stat-Signature: k1kd3tfd9ahpj6jjh1ntf1f7rtskbfx5 X-HE-Tag: 1621428410-971826 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 Wednesday, 19 May 2021 10:21:08 PM AEST Peter Xu wrote: > External email: Use caution opening links or attachments > > On Wed, May 19, 2021 at 09:35:10PM +1000, Alistair Popple wrote: > > I think the approach you are describing is similar to what > > migrate_vma_collect()/migrate_vma_unamp() does now and I think it could be > > made to work. I ended up going with the GUP+unmap approach in part because > > Christoph suggested it but primarily because it required less code > > especially given we needed to call something to fault the page in/break > > COW anyway (or extend what was there to call handle_mm_fault(), etc.). > > I see, thank. Would you mind add a short paragraph in the commit message > talking about these two solutions and why we choose the GUP way? Sure. - Alistair > -- > Peter Xu