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Mon, 13 Jan 2025 11:18:52 -0800 Date: Mon, 13 Jan 2025 11:18:51 -0800 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v5 06/14] iommufd: Add IOMMUFD_OBJ_VEVENTQ and IOMMUFD_CMD_VEVENTQ_ALLOC Message-ID: References: <86e78625c48d0c8fb815496dbc57708b98a46ec7.1736237481.git.nicolinc@nvidia.com> <20250110174842.GI396083@nvidia.com> <20250110194950.GI5556@nvidia.com> <20250113191225.GS5556@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250113191225.GS5556@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF00004FBF:EE_|MN2PR12MB4109:EE_ X-MS-Office365-Filtering-Correlation-Id: 484d9825-15fb-4625-36c8-08dd34072350 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700013|7416014|1800799024|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?WdfEqEzohrbPn6H/32PuD+r0eOGBQDXEConVMCq9piUlNL4Wle3qLd5qTdVI?= =?us-ascii?Q?Mz/qSzGioxQ1k4r1YVJ7Sxx/ZnHqk6QGktRfTWhH6kvKeB4XtYsX3O1A9Fio?= =?us-ascii?Q?1vgDpLbanFEVPr9L0pDZ68DFTgCiW06wPrOcPHhR7aeN+oS2gkDTtjO4aLmD?= =?us-ascii?Q?nHzKboFOs0+WU90StAzZvzScYxqu8CaWLXW12h1A43Rr2c8sfBR1/6AQxtah?= =?us-ascii?Q?f5MoXsSFw2YkgTPotdqzgGF9ORRhnIFJHF0Kin0xvrOHNcK46ITUGOmSCwKU?= =?us-ascii?Q?zwS3LgXeOBZfvpy419QLN84D2Wa/agmkgUz4rlMxR3a393/rKrzkoRbhwExD?= =?us-ascii?Q?xhlmj8TlKUiUJ2nsU3I08YeCzTw/YaZg/nhdTPfmDhM8gbc6gOZMwwsyBf5p?= =?us-ascii?Q?KJ1T8bh30k8nevy0v7URcvHuabjCYlwXfFmOhSi36Z141Jo8c/ifsqyGkwMB?= =?us-ascii?Q?ukI34DTpiOUn3EClszjKHJG6hQzr1f3sZHYeViYWaXxtQXDF223GzoFCFVw9?= =?us-ascii?Q?irT98O8N19slTY4sBX8Sjvek8AZPv8xGAOnw4mlkG7SsBIBr9EFkL0OPbhPI?= =?us-ascii?Q?UMeb3FOZbWH/xFR5PnbWko64O3Gue0bDd0i1yGkAfgdpa7NXifq6gvMKHLsf?= =?us-ascii?Q?8Nw3at9lfTAUn9Xd7iWofmog6gLtkruKlblbTfaE3MMU8n3WXEvys6NF/Sqn?= =?us-ascii?Q?iDhPsF7GSjUUzNqluyFzDRWo+k5trIxrbaXYxw/KOnTZAAIYWmUS+jJF6ZZP?= =?us-ascii?Q?U3S4uI8xkUZw3m9b8cL+g8PkcyUx9Mdw9v+sz3yB8CWAXSyWX5Kx2Pg4rg2u?= =?us-ascii?Q?3ttkyBmp9HaqKeqGmbrS4ZqA5HO3PlJb+OcMCfoSlO9Wx1HzfYIAmPj24Qiz?= =?us-ascii?Q?Mhh+LNazN1ms1jzJMJs/+X+1Z4b77LKCK8IHUbcNW6BpOesSoZHaBzgoDnib?= =?us-ascii?Q?WExMfsaWyYxhrxB6UMvXcvaFzqFofY9EDHZ6vwqqUwaA2II6SYEagwYh2ige?= =?us-ascii?Q?MI+UCDzwC71naQ+jFxzRGhONPpimy1OTJonywJadGoUnIBFUMdiPTapFpuy4?= =?us-ascii?Q?yxyFMKu6gRcCPLVXX0EWYY2omZLsteCJja1AWlbBmyAiKGdDE8cayeSN27oP?= =?us-ascii?Q?LGmP24YqTzdPkHigwH1YbYfTZwDVj4c6OY0IA8hYObjZcaokgQ/v+iug/3pF?= =?us-ascii?Q?aCS9vcHKFjXKlIu9RWjSYuM0OpVXF1AFD/ye6BM45YGg7y8oq75e69QMTGk9?= =?us-ascii?Q?Fk+3hHB6ki16MHXCwlbCo5bO28trRi23Ht01RVV7fsrRPmNlOcvQCPUS19Ml?= =?us-ascii?Q?DjwqgX3c6a4sYHMOh6Of3n1mQ4eSwfsP5/S1l7StkQh8yaLyuYtDPTosqByB?= =?us-ascii?Q?x/0NTH9fX4QOnu8qMBoPpyjfr2vVDym7gSMXRhOX4t6tgTKdbhjk2tzPOvsZ?= =?us-ascii?Q?AkoqC7NfOsnDkfvcLOmwrHAu+wOJzTrHMuZW3ikNVo5S9PNhZmK4ZA2ctnTd?= =?us-ascii?Q?2e+a5UuJ11RVGOA=3D?= X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(36860700013)(7416014)(1800799024)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Jan 2025 19:19:01.6478 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 484d9825-15fb-4625-36c8-08dd34072350 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF00004FBF.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR12MB4109 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250113_111906_162167_C7A04614 X-CRM114-Status: GOOD ( 15.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jan 13, 2025 at 03:12:25PM -0400, Jason Gunthorpe wrote: > On Fri, Jan 10, 2025 at 01:58:21PM -0800, Nicolin Chen wrote: > > Hmm, it seems that I haven't got your first narrative straight.. > > > > Would you mind elaborate "copy_to_user() can block while waiting > > on a page fault"? When would this happen? > > copy_to_user() is a sleeping function that sleeps if the user memory > is non-present. So userspace can cause copy_to_user to copy to > anything, including memory that is non-present and will take along > time to page fault in. Eg perhaps by abusing userfaultfd. > > We should not allow userspace to globally DOS the iommu driver this > way. > > So do not hold locks that are also held by the HW event path across > copy_to_user(). I see. Thanks for explaining. I will add a patch fixing the fault read() and change the veventq read() accordingly. Nicolin