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Shutemov" , "x86@kernel.org" , "Tian, Kevin" , Pei Li , David Wang <00107082@163.com>, Bert Karwatzki , Sergey Senozhatsky Subject: Re: [PATCH] mm/x86/pat: Only untrack the pfn range if unmap region Message-ID: <20240723214412.GQ3371438@nvidia.com> References: <1a0884cb-39ed-455e-a505-7c1b2a0e5225@redhat.com> <56c982c4-9863-4134-b088-8dfb4b94c531@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: MN0P220CA0027.NAMP220.PROD.OUTLOOK.COM (2603:10b6:208:52e::8) To DM6PR12MB3849.namprd12.prod.outlook.com (2603:10b6:5:1c7::26) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM6PR12MB3849:EE_|CY8PR12MB7243:EE_ X-MS-Office365-Filtering-Correlation-Id: c53d8bcc-7d10-489e-a662-08dcab609826 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?5nZ/Hezrc9xTbhVAODeo44yejrWJFxSBlzuZgoaQZOM7nXqQJmtdgcqSSFhS?= =?us-ascii?Q?JV5YcytWGsT4KmFFGUOYdBeGdoK3auwIkgZDAWBgey2TxvFRRsU55jrKJMVP?= =?us-ascii?Q?mZ7xFj5pUiQRkA1YEHIEU4TQCY0re8b4ucc0HKFbtTA8oBbNKQMbV0Re9i78?= =?us-ascii?Q?f5+nJ3i2EFcChKxuTwHb4rqSaKQphKCqj79COZYTXkAU7DtMqAbb7bL4jxaT?= =?us-ascii?Q?DLUkUKPrSKWZiHfpkTTt9OEqW5JCNl9AYKOLNrJUrt8VMlkCTyxYZWbCEczo?= =?us-ascii?Q?xgVT9vnaNJN4kLQR3/PHv4l0b5w+7JzwhT4WzciRnfDB+6RkP3kBpkAWW19q?= =?us-ascii?Q?zmuGBex1iz0nC74dCR3Xv1Qe2BSXo8VX6EU8NF4a8vGbxFJdzY3dPlqDlQjt?= =?us-ascii?Q?69eZ5+SIJgBU8i3pGK/IzITIsQvSQ/vAmN5gxYRRuegZaIHyYokNK1gHvCID?= =?us-ascii?Q?j5tF9Vh4OZBVNPheZ4uaZnOhLhpv4Er7jwxzNLBdy9GY0lZHwHS74ynAW4SJ?= =?us-ascii?Q?hKGawtqvbNc/s7PjfQjBYJIwnqYzHkLKQ/7Ytj3BlxXcLkiv6IQbKBtKzi17?= =?us-ascii?Q?gbKdA8/XrNWmxf5oUAJrYCXS5ZzUR3QQVHtXhejrYBvd19J3Z60jVl//FbXp?= =?us-ascii?Q?xltwdesE2qxsZgnfDBNwt9Qy7ncyKekD03iSoMVfR/QaBX63tgGy/cFwJbKj?= =?us-ascii?Q?fwtQ9O/YrWgpvPp1m21hEpX6FwsIFd54488MnUgm39X79tq2Lrm9zzsMF+It?= =?us-ascii?Q?iBJ1p5o6XdmDScCh5f1szeoYmUkTAKO9V9Dp8PpXmAFGLs7SojHjvmcUWb1r?= =?us-ascii?Q?gFAD8jlZN+pt/jTAxWnOHCVSrRrplr/7HY9MQqx+yNObYWx3erzTqiXLmAQO?= =?us-ascii?Q?RctuaJzvlIk5KpHX21NY0XSyk95xAlSoQ9OQIOEEdkocYy+J/Abrtd+gk32V?= =?us-ascii?Q?yF0lGJvzG+1bBIvWg80kcwZ7JBMMtBc1b504LKF0sSW7SH9sSalo+vn/POMV?= =?us-ascii?Q?z/uUuDnV6XTRrEJNIkA6gW/UuTsJKTVHbWDSlPrV4Kuoc58UP7dLSXrDQPaM?= =?us-ascii?Q?ozWAa/LcErrK4n6uXvTDPwPygb4VgrEBtScSSygv2m4pB7co4KPf6oHYOlKI?= =?us-ascii?Q?+rMMBQMgpbGgqJO3iLXtEmVPXjrM9dl037yjKmEntei2GrEIaBlznhyRUzHP?= =?us-ascii?Q?nbkey4AkFbjVInLslenNs8OgqkBxPe24cIJHeOYj8Adshl3ae63H/8uCuA8Z?= =?us-ascii?Q?po8y4C5g3s/XQgiASkGthgi9zyNtK5dKfKBLRCYLSVQ+/aU6LAYtaCiK4VMb?= =?us-ascii?Q?3YzcT0eqE5oywq1LNtZdhNDlnLxU+z3l+pzzuTuXQufXV0iCXLp9kUTZPW2w?= =?us-ascii?Q?9Jy47lHs5RBmzY0Fq0opEj4W4hghMOIZKWXK0OdQ2uTpgbDpaVnfM4Kj004d?= =?us-ascii?Q?veCUu5uER0zvOJWfM2hs799J/NbHv3PDEB0OPjlrRFIkQ8LBEB+mIwNz0htw?= =?us-ascii?Q?7exdsGYSxvHZWX5h+pwW63eUN1x90EZixckqHyN7ChfSzkXfQKBZDAgcoAaH?= =?us-ascii?Q?Xb2jh+8Q9V4do0NsAeY/8v013MZedfKYWVYbYFRU?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: c53d8bcc-7d10-489e-a662-08dcab609826 X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB3849.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jul 2024 21:44:13.8968 (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: HacAJcjUzaMVwLQFHkNL/7DBHTfOQcyc4MJbwJFOmWpCOpLLUG58QTFsKkAwQlH4 X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7243 On Tue, Jul 23, 2024 at 11:36:51PM +0200, David Hildenbrand wrote: > I wonder if we could just let relevant users do the PAT handling manually: > I'm also not sure how many remap_pfn_range users end up triggering VM_PAT > code although they don't really have to (just because they happen to cover a > full VMA)? > > One nasty thing is fork(), I was wondering if relevant users really rely on > that or if we could force these VMAs to simply not get copied during fork. > During fork() we have to "duplicate" the reservation ... I admit I barely understand what x86 uses this PAT stuff for - allowing WC mappings is part of it? If yes, then RDMA would expect WC PFN MAP VMAs to copy their WCness during fork.. Jason