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Thu, 13 Feb 2025 12:56:20 +0000 Received: from CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732]) by CH3PR12MB8659.namprd12.prod.outlook.com ([fe80::6eb6:7d37:7b4b:1732%6]) with mapi id 15.20.8445.013; Thu, 13 Feb 2025 12:56:20 +0000 Date: Thu, 13 Feb 2025 08:56:18 -0400 From: Jason Gunthorpe To: Yi Liu Cc: Baolu Lu , joro@8bytes.org, kevin.tian@intel.com, eric.auger@redhat.com, nicolinc@nvidia.com, chao.p.peng@linux.intel.com, iommu@lists.linux.dev, vasant.hegde@amd.com, will@kernel.org, Suravee Suthikulpanit , Robin Murphy Subject: Re: [PATCH v6 09/14] iommu/vt-d: Add IOMMU_HWPT_ALLOC_PASID support Message-ID: <20250213125618.GX3754072@nvidia.com> References: <20241219132746.16193-1-yi.l.liu@intel.com> <20241219132746.16193-10-yi.l.liu@intel.com> <38e26d9f-0727-4b15-8e1d-03d262c15c8c@linux.intel.com> <5c5180cb-9bbe-4fa7-b109-5dad2ca9516a@linux.intel.com> <20250212125930.GQ3754072@nvidia.com> <2399c639-b9dc-4c7c-bac8-3776cf6a88f5@intel.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?T78M8bR3tXCslbI32mNopys0E1byqLbSGNPt6VDCOpdTYnNkjJSSYlpgXiZg?= =?us-ascii?Q?BIo1Ni7x/XdvGwvzcKMPKKy4Wfi0MgyUKuP6psKzSfF4yet24frqXqA4a5EJ?= =?us-ascii?Q?ZNmPsJtX8TKTcRlGYrP8x+DEDiV7Z9HeaM6wdaJcq0SNeytzPjoxQ0tuDsmR?= =?us-ascii?Q?7vUn5+wqQi2tVXWH24l63O7vlWr+Za6LY3FnDv/jmUmn7m882NFpKv9LYr3x?= =?us-ascii?Q?54XfmxsVzC+TmF79dxVfkgxZtmE3h9tZGrSfgU45pGPfoxCcFQWEdvxOjUXf?= =?us-ascii?Q?X77ourrnw3V8B+KgAdTmeZrMtmP8rTM1rt9IEWaxLOksM7vpsVDQq/qc/mHE?= =?us-ascii?Q?olbg4sRtay51c0wUL+xDJbluTzJ49oWIxr1KxBWCwiRYN5t9i+9yEzGiHK9Z?= =?us-ascii?Q?QFizVyzhHZhobizF8kroMeXeW0M+3lF2WS6O+UkYiAw9pW1nhlbE4AgRfhnP?= =?us-ascii?Q?EhLZdP9BqHPxCpBj4LKUllYXxZkntI7Q40rTZispvmZUm7IFbAVszfseLChg?= =?us-ascii?Q?nUM4oiUFFbmC6xOsAl49TZJDt+/gneDHQU7GkeKsv5mUtVeqY2lkzCmA8ydJ?= =?us-ascii?Q?NVXvyBq++RV2VMhk+h5s6HlRS7nexzwV8D3xBYRn/aBS2S77QDJsrkLKyJSB?= =?us-ascii?Q?NYb9a6E4Uzvj/FYI8dW0JvW4y+Q6pNU6UdBupgHJRwzOqB1Cs+vWuiy5ioRT?= =?us-ascii?Q?k7diTL7tmu46iRnH8Z8BUPafyR5ue/xKjoGgC5lKEuqCrPtxEy/VSH9iFWe5?= =?us-ascii?Q?+CaoJQqOfI5wLwrvzYwxmLhm1Khf/gKj6ZRBZbYlPGaAfCntWgSvGlV3yXU7?= =?us-ascii?Q?bBy+P3fi2an6+3p398GalCOQQfFGlVZdCaXp5GRM2dDZ9fdyurMNmJuaxYY5?= =?us-ascii?Q?wUiOgMkq1kIY9+oFcLgFs2j7F302vg+aePe+x9qNY6qoQmgrs4mqNiZD6wQ8?= =?us-ascii?Q?oT3kDtRfs4FUHHzYys7dOxQFhLBBxCck9HhtMFgjAKe2gxI5ErGoQ2/ox1++?= =?us-ascii?Q?trIIaQJv9AFophecXZq2JElNGbuZWYFqc0dFR2UCU2jknB8mga5g6yslRFAl?= =?us-ascii?Q?0Ynk2guNWgWPdr+CmAfp6kR27REJMclIMZ5+JwlyjagugU6eZtD4vCHMUuQi?= =?us-ascii?Q?cLPPncG4v47K5aCxkr19jpILbzlYI3mvwbD6mZtqVvUAcrcQscrI2nnO/lTU?= =?us-ascii?Q?z1YJWnzQojCAFrJtNIgwunuKwXq9UkmjRg4jOM6CuIsafpWfXmcZ+nXFAtBS?= =?us-ascii?Q?Q76uZcLD4B2ulu00vCcTLNdu0zfISIEcysTgV12PsafT3B9I8OXsvUW/+qyu?= =?us-ascii?Q?lerkYN2KlDfz2v6hEja8KgVyb6ezrccEw56I17/9hjt0Q4d+N/pJTeGfyY3X?= =?us-ascii?Q?cSZHLFYsKbYToVr5zvjqzXcL97XNMpS/H39bWpwnl7KjLgpNaWbYJ3MVhhUp?= =?us-ascii?Q?t1aUnPdvj7l4mSVfHKArLfpdk6P+fHGPfF0W8rB3UNQehZLO0OO8xYJEJFeI?= =?us-ascii?Q?R9w/L74gYtCZnFzH5YY4R/mCqHN+FtDoSCdwj60bQPVoHiGSfuA23TciXA2J?= =?us-ascii?Q?nQG7d8LxVcFbsxCjZl4=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 64c774c9-8f75-4104-357b-08dd4c2dcfbe X-MS-Exchange-CrossTenant-AuthSource: CH3PR12MB8659.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Feb 2025 12:56:20.0921 (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: MWtC+kf/5mAS2S4dOHjuyMiHWaONdJeQXuL36+j/zdVbzu7eoJKbIFQQOlOTakaS X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB8801 On Thu, Feb 13, 2025 at 05:34:52PM +0800, Yi Liu wrote: > yes, as iommufd always pin and map user pages for the paging domain, so > I don't think there will be any PRIs on S2 due to non-present pages. That isn't strictly true, a misbehaving guest could deliberately setup a S1 that points to a non-present S2. Ideally this would cause no PRI into the guest and the VMM would fault the device. > However, PRIs on S2 might occur due to insufficient permissions, > potentially caused by userspace. Nonetheless, I am skeptical about the > existence of such use cases. What do you think about it? I suspect it is "OK", we already have to be safe against a misbehaving guest creating a PRI storm, if a misbehaving guest does it via pointing to the wrong S2 or just not updating the S1 doesn't seem to make much difference.. IMHO it is desirable for the HW to provide a way to disambiguate the PRI. Jason