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Thu, 4 Sep 2025 09:32:04 +0000 Date: Thu, 4 Sep 2025 17:31:06 +0800 From: Yan Zhao To: "Edgecombe, Rick P" CC: "seanjc@google.com" , "quic_eberman@quicinc.com" , "Li, Xiaoyao" , "Du, Fan" , "Hansen, Dave" , "david@redhat.com" , "thomas.lendacky@amd.com" , "tabba@google.com" , "kvm@vger.kernel.org" , "michael.roth@amd.com" , "binbin.wu@linux.intel.com" , "Weiny, Ira" , "vbabka@suse.cz" , "pbonzini@redhat.com" , "ackerleytng@google.com" , "kas@kernel.org" , "Yamahata, Isaku" , "Peng, Chao P" , "linux-kernel@vger.kernel.org" , "Annapurve, Vishal" , "Miao, Jun" , "zhiquan1.li@intel.com" , "x86@kernel.org" , "pgonda@google.com" Subject: Re: [RFC PATCH v2 02/23] x86/virt/tdx: Add SEAMCALL wrapper tdh_mem_page_demote() Message-ID: Reply-To: Yan Zhao References: <20250807093950.4395-1-yan.y.zhao@intel.com> <20250807094149.4467-1-yan.y.zhao@intel.com> <281ae89b-9fc3-4a9b-87f6-26d2a96cde49@linux.intel.com> <87fe45aae8d0812bd3aec956e407c3cc88234b34.camel@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: SI2PR04CA0007.apcprd04.prod.outlook.com (2603:1096:4:197::19) To DS7PR11MB5966.namprd11.prod.outlook.com (2603:10b6:8:71::6) 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: DS7PR11MB5966:EE_|MN2PR11MB4712:EE_ X-MS-Office365-Filtering-Correlation-Id: 92824a9a-e2e3-486b-5503-08ddeb95e8e5 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?u78Z83TO6uWTaE+AvGYMFjw2ZiV/opQBYE3OWNHUIqvW1kDbHl2Wys5RV+qH?= =?us-ascii?Q?iQHJXJQwR4dPMoy1OuXjkblq3mkZKfohEXuX9A/gimGORhY17shHEX/BoMSc?= =?us-ascii?Q?kEuyqT1qSfltGcXbZX7qFBDzzTP8WSRW+m3XB1brDU2yAw0tuGkLgZLVvqmm?= =?us-ascii?Q?O5HwUREoQNE3yfWIFQStCffestvMcLeMChOdaMGF1Bndstw9Q50NIc5HUtlb?= =?us-ascii?Q?jEEzH/G5rTKvPTCao94vMFN4+6ozMlocWYvEz8HpBjjY0pWo9EAopX4pZ45P?= =?us-ascii?Q?pSkyr2YYlFyeBASGh6wFSDjeT5ZcKy7Khs3T/hHpRZx9Z6mrEjQxAC5FpRjd?= =?us-ascii?Q?nyY3c4XhIoRM8HjV52Y96xQWTw4Mb6Jkw3dd96ruw9J9ZLP0hgZagAnJ9Qoy?= =?us-ascii?Q?WYAVxduJUBnuRGbU3+gRcbGLbaZDf6zQxf9N0tOTI8lwrFzZ7qg5Gjy/3IWw?= =?us-ascii?Q?qnLYNPpydaCspE6EDWyOamjCRkvClEuc1JneaLYdhaB+ZFjmIHzUDP2fb/OA?= =?us-ascii?Q?6oSFCtaNSHm+VNes22QqDdQJGMhtcO0aCLIFcZacIXxpBYHLXTV9H/hTsq/C?= =?us-ascii?Q?vCZL0w6W/el6yJMVQ+adpkS2VloJD6P1ws24INCscWVwtsgSBY3aCaLHGID8?= =?us-ascii?Q?C93mXYHmAfIVamsEtHNs+GMk4xTAlGxTdcLp48GOGVnD0HoNvXP1D5A4hdr4?= =?us-ascii?Q?kVF1hrRFpYggJp1EWTDgugGGCUrdNCdMr1KZ5XPKPbwtLuDtMDf1mpsh+0As?= =?us-ascii?Q?kZgANhau6RMCtAdJ3ucCLuF/duUH79Onf2JuVq24oXwacmVqYbLDFqjDeo0I?= =?us-ascii?Q?JsP+dz3Tp016LSWDX9Kc7VT9h670X0oO9bY1tcS0WPJoqVCoBnI20U0Qk0kI?= =?us-ascii?Q?qADQZtFOGwJil4rQgQPqbZqn57C7mdeqXPtr6ajfsawWs84eH10+MCha0Kh6?= =?us-ascii?Q?xyo8Iz2GLRs/MMkBbfWwWApBXi23BEX/qJiMREtRj4YLmQXNGagyphKzrAVz?= =?us-ascii?Q?Cg4idc40zRVDLWRtDBHFu27Ilq8aXN1/4afb/3YyLqKrrUqJjs0LQ7UktMKm?= =?us-ascii?Q?gk5bio1YCcCIZEI2w1bkNkCPS6V1xm0OBaOfpa91biltJhbe84kcVnEMM+EG?= =?us-ascii?Q?Exz45X7XT/4xUrf41rJamgs2UOL1CG8oFbIfCpN5V3g+y9hh0QYiTD74xcae?= =?us-ascii?Q?iFfyiu6lxC99oHCLZr0lT6l7lK2r5bIZ38JInKU6LraJ/prXaF6UHvFxVB3e?= =?us-ascii?Q?LVfKw+5veScJLa2BAsYx2TNhtYiYttfLiqFB7vHTIEw+qM5cyHD+9/eUmEUl?= =?us-ascii?Q?cuBL/j+sTh3nJVVy5dEIrJ1+tGuzu77mtGAS7SZg4IIq9WvxJlEqXaIgKIxa?= =?us-ascii?Q?ndvRFX+e8SI6UPT2gb9nWcyLtPvZrU02/IDn/e3cXzKkOlSuk7oW1oq1p9TR?= =?us-ascii?Q?TIdmVjNqc/143h+3DAkfUr3Ppi0TD7NDCs1MrWKD4nBFNMU0iUD9qXWMeHXQ?= =?us-ascii?Q?LOQh/nrZfwEXNshGrnstYKZ3uLuXB5vN01/icoYWWRrNeph4nLsrSU1PyaXO?= =?us-ascii?Q?1//DIopUs/lpsxDusidmU1b6yGgNXG0fJP0EuODz?= X-MS-Exchange-CrossTenant-Network-Message-Id: 92824a9a-e2e3-486b-5503-08ddeb95e8e5 X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Sep 2025 09:32:04.8566 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: v9Q9HN/NprGyDTPAkO+JQRRfLMrYrzZUaO/8+ZD2+eDkRb1vdgkE2dSTKE7qz759XclBNbgFgBR23gWLaRRUgA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR11MB4712 X-OriginatorOrg: intel.com On Wed, Sep 03, 2025 at 01:45:27AM +0800, Edgecombe, Rick P wrote: > On Tue, 2025-09-02 at 10:37 -0700, Sean Christopherson wrote: > > > If there is a flag we could check it, but we did not ask for one here. We > > > already have a situation where there are bug fixes that KVM depends on, with > > > no way to check. > > > > > > I guess the difference here is that if the behavior is missing, KVM has an > > > option to continue with just small pages. But at the same time, huge pages > > > is very likely to succeed in either case. The "feature" is closer to closing > > > a theoretical race. So very much like the many bugs we don't check for. I'm > > > leaning towards lumping it into that category. And we can add "how do we > > > want to check for TDX module bugs" to the arch todo list. But it's probably > > > down the list, if we even want to do anything. > > > > > > What do you think? > > > > Could we taint the kernel and print a scary message if a known-buggy TDX > > module is loaded? > > If we know which TDX modules have bugs, I guess. There may be some bugs that > only affect the guest, where tainting would not be appropriate. Probably would > want to do it at TDX module load time, so that people that don't use TDX don't > get their kernel tainted from an old TDX module in the BIOS. > > What would you want a TDX module interface for this to look like? Like a bitmap > of fixed bugs? KVM keeps a list of bugs it cares about and compares it to the > list provided by TDX module? I think it could work if KVM is ok selecting and > keeping a bitmap of TDX module bugs. Specific to the problem of TDX_INTERRUPTED_RESTARTABLE, could we choose to port this feature to all old TDX modules?