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emacs 28.2 From: Alistair Popple To: "Yu, Fenghua" Cc: Lorenzo Stoakes , Vinod Koul , "Jiang, Dave" , "dmaengine@vger.kernel.org" , "Zhu, Tony" , Andrew Morton , "linux-mm@kvack.org" , Christoph Hellwig , "Shankar, Ravi V" Subject: Re: [PATCH 09/17] mm: export access_remote_vm() symbol Date: Thu, 05 Jan 2023 14:22:28 +1100 In-reply-to: Message-ID: <87tu15u061.fsf@nvidia.com> Content-Type: text/plain X-ClientProxiedBy: SJ0PR03CA0228.namprd03.prod.outlook.com (2603:10b6:a03:39f::23) To BYAPR12MB3176.namprd12.prod.outlook.com (2603:10b6:a03:134::26) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BYAPR12MB3176:EE_|IA0PR12MB7529:EE_ X-MS-Office365-Filtering-Correlation-Id: 4c87e9ab-9b25-4d33-382a-08daeecd638e 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:BYAPR12MB3176.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(4636009)(39860400002)(366004)(396003)(136003)(376002)(346002)(451199015)(66899015)(5660300002)(7416002)(41300700001)(316002)(6916009)(54906003)(2906002)(66476007)(66946007)(8936002)(66556008)(4326008)(8676002)(478600001)(36756003)(6506007)(6666004)(186003)(83380400001)(6512007)(2616005)(6486002)(26005)(86362001)(38100700002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ixXeE+CmQsQv8R+HwqrhAEVUVSBkVwur3vOcTirjUV8HkVAwfwJpks67Z1iu?= =?us-ascii?Q?n5kYyNLBxLu04ZwaDfseDe/ZvV09pl+fxIVehID2o/al0GKrSq7Zcuxm7616?= =?us-ascii?Q?HdLfpYag2Vymh83cUIJeROWTwcWJJfGClHWlp/bKYWBgzWlk9nG2REBAvOzY?= =?us-ascii?Q?oocnUO3vU0zQa33aD7zdWGhcs0tPqcGhKW4BaNi7VMgZ/4lJnHv/FXTR/Urx?= =?us-ascii?Q?2jphynldEpJ4WB+1sTebqnkfhuWAVG8TSXXCPubx4jksfeap58Su+islLZjb?= =?us-ascii?Q?i+qll9KTt3zpvfwvwuCtuJp/WrtrtNnHnQsIGJ2WfzxpBNXhYM7D8DA3XlW7?= =?us-ascii?Q?HcDDX8HjzBA1m5rDkFmSICAl1JS60NOM8QFepau9kvVui3A12Md9p/bzrNDS?= =?us-ascii?Q?vKB8ke8DyydRTiLmN/1Yy7lZKsN62iFqWt4Ggp1IlJS7A6G758N86SJvKT6M?= =?us-ascii?Q?AOfXjI0KsJFxlzooSQWh3WMUhDoaY+B/66+GYXsGkQNpoKF9vXeTdf+lTQjy?= =?us-ascii?Q?L8Wjhl1fdGFkCipj4ySm1eFoO1uLQAw94ATewIY0H35u4JklblCKExmAOMfC?= =?us-ascii?Q?rkSgDVag+1o1eybc8Srjf9uN9oygkJBhvxVZLM3kR6qA8rd+yvTmBR9THDaS?= =?us-ascii?Q?X+cR9oVTDwt4g4TUi+vljnqHaAS8sCRPgHfgPXtecieg3rXudYawba69/aHl?= =?us-ascii?Q?eSPE3PJ3AELGt10XEjd+osuZu9R4Mb+KU8OpblAvtgugryP2rFpQdwtVp5na?= =?us-ascii?Q?zNU7Apz/PyzHgN/UQ5k2WPH1Moc+qj9HeCE/sr4ALoKxc1x7g792XaNFtWip?= =?us-ascii?Q?W0t6h1ns8qEHcNhcf447QFbhiXUe4P2zwTrCbS8E6cFxgqjAQtVfy5214q+W?= =?us-ascii?Q?s4qO9mhW+I/m3rm+N2nLkDlaeqQSrpkSWuoYWZAcUmyoNNLjM1OHF7qXpUvF?= =?us-ascii?Q?mxtjX7P31Z6GnLQwFxfA1vScLkxPHW0vI60lV9cS/XuLKFcLUaBnfUBvpHqz?= =?us-ascii?Q?wLqkBQzkUQD6l0KIeI04cqPiWkCwetmqMAkwDiWkKIsf3uUSDlccYYWUiKnl?= =?us-ascii?Q?olgdD3vvgYu1BhitUCCKRZbiKqyDoxgBO2X+OSVfFd7XKRn0DL2POJ7NtZ60?= =?us-ascii?Q?ldb5Ux2xfwKxIO/aSH200cHHm1JZ819m6YAchmG7cPVIJHPdiOIUExhPSY99?= =?us-ascii?Q?Y7uXS1bIrE2Jc9ASkWVDi+aiaEAQtrShi4y2tZKrxcobEf0dKiuQuevqXBYR?= =?us-ascii?Q?XgyYM5Qa6HZpV5QfsC0LC1FaeuL1Mgl+QVSGVxpKZDdeV7/tApQXmPgyLnnA?= =?us-ascii?Q?oI3P0uBsS4xmRbYwAlzoYOgPLpGbTrAyytC8FlJ73Fst2Twepa5NZrVxCcIT?= =?us-ascii?Q?IkGxCgOsEqPHf6bapseR8KBzJ7gt8FHfWHtmfUN9CMYzvwbDLGiRZvlu6yNu?= =?us-ascii?Q?qIIsdUhFBdeK+FtJb6ssNDRyTxRZXt+k73tDPn/sHZU81pDeLBouF+3Pirf3?= =?us-ascii?Q?emEPCUQjqkNjC9jnLqrc6JZk4sZNLkxAqEiygcBCazZB7ADzbTwTiMV9MZ0B?= =?us-ascii?Q?31jq/AgjlSDorMeJg5yNYZkFBdrolNHK6pie47iS?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4c87e9ab-9b25-4d33-382a-08daeecd638e X-MS-Exchange-CrossTenant-AuthSource: BYAPR12MB3176.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Jan 2023 03:31:53.3880 (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: hlcUlrMOOAvKTa4EXFHghAWFr//KwUpUZ3JpZJskzf49hzlvNesevP9Y2EMCQ7VdSxvJ8w0G/jAv6skzZQ6BUg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7529 Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org "Yu, Fenghua" writes: > Hi, Alistair, >> Alistair Popple writes: >> Lorenzo Stoakes writes: >> > My concern is exposing something highly delicate _which accesses >> > remote mas a public API with implicit assumptions whose one and only >> > (core kernel) user treats with enormous caution. Even if this iommu >> > code were to use it correctly, we'd end up with an interface which could be >> subject to real risks which other drivers may misuse. >> >> Ok, although I think making this an iommu specific wrapper taking a PASID >> rather than mm_struct would make the API more specific and less likely to be >> misused as the mm_count/users lifetime issues could be dealt with inside the >> core IOMMU code. > > The iommu specific wrapper still needs to call access_remote_vm() which is > in generic mm. We cannot avoid to export access_remote_vm(), right? The wrapper still needs to call access_remote_vm(), but that doesn't imply access_remote_vm() needs to be exported. I think the logical place to put the wrapper would be in iommu-sva.c which isn't built as a module, so you would only have to EXPORT_SYMBOL_GPL the wrapper and not access_remote_vm(). > Are you saying the iommu specific wrapper doesn't need to the mm code? > > Thanks. > > -Fenghua