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Tue, 4 Nov 2025 09:32:37 +0000 Date: Tue, 4 Nov 2025 17:31:08 +0800 From: Yan Zhao To: Xiaoyao Li CC: Sean Christopherson , Paolo Bonzini , "Kirill A. Shutemov" , , , , , Rick Edgecombe , Hou Wenlong Subject: Re: [PATCH v5 1/4] KVM: TDX: Explicitly set user-return MSRs that *may* be clobbered by the TDX-Module Message-ID: Reply-To: Yan Zhao References: <20251030191528.3380553-1-seanjc@google.com> <20251030191528.3380553-2-seanjc@google.com> <969d1b3a-2a82-4ff1-85c5-705c102f0f8b@intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <969d1b3a-2a82-4ff1-85c5-705c102f0f8b@intel.com> X-ClientProxiedBy: KU0P306CA0095.MYSP306.PROD.OUTLOOK.COM (2603:1096:d10:22::8) 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_|IA1PR11MB7942:EE_ X-MS-Office365-Filtering-Correlation-Id: e1f6f621-7b78-4ab1-f02f-08de1b85175a 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|1800799024|366016|376014; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?t5rLIVrX9u8MOPe2MeVeSTtTLi1xyp9rhAIMK/jwE4hTqM2mw7r5/DwBVZem?= =?us-ascii?Q?5Xo+Kum1P4ivyJGtL7rv3qgn/bwamOLLvNACoAxm4mazZ0Pk9IjaxHmC0OrO?= =?us-ascii?Q?q4Er5i2Wll6wugGe3sfmRNRfuJdKuHxP+VFZvqiaOx+w7d4HKHEGF7FFgwJP?= =?us-ascii?Q?9whWNCDiD74Qi/nSNahmqZCbeFOaEDKjHEZUQF/P5RJ4jDH+Jbc7vAUkAKBh?= =?us-ascii?Q?LsxicvZ4+C9QCJVai9l3+9mp4GG3qukdk7hZUb9C0wZQx8+b+Bwbqd4XHei1?= =?us-ascii?Q?l4qL0BhTkeLe/vRhyvhq2bySFkTjEJl91ZAAcDYEMBL421dmDEhWOeCyOIyz?= =?us-ascii?Q?5N0pl84OWBRF0Y37MEaoO7c+2L2CubFV3j0WqJK7A/81PJK6h2v7dEalytop?= =?us-ascii?Q?3wmWZtdNvaij9iPzxgqbWGbWvLKV9q2g/k47CvVECwB9Ex+pKjqyGrNDhSjB?= =?us-ascii?Q?97HNO/jw5Ihs/wFBNzA5QWKXv9hbHajrftok7qNwqm9yzgZ2ccx73JAujydQ?= =?us-ascii?Q?6qTUDZNMe+yeYFuufJj7LZieCeSRJimnM4jPB5z2vMsKqg4bMiiopEa3kKDk?= =?us-ascii?Q?wsMwiJY49SrK+pxsuSvmcDSgNNvYe4qUupWFtpc/aGmOVRMGDhUb9dhdDIFk?= =?us-ascii?Q?8l4vs98UkuxgFiO8RzfPq3UX/kDgDGFD5MPNerPB8SjzQAT7l5AmyrDqz+FP?= =?us-ascii?Q?wLew2qzS+Fay0U7EWZZiWFRzHsVO1al1n3ghl9iVfBqdky6jk+LTV2jBZdh4?= =?us-ascii?Q?S0lUVXjaUzxVU6MRB1qyt9eL9Ti3UfIdYOMCSRM/eO+r28Eec3jn06YmU9MX?= =?us-ascii?Q?yTQzeldfoZ4htk5YPvb3QPvm1or2UkyDQLm4rknMoBuTLCXuLracU0xDRdxy?= =?us-ascii?Q?ZgSgvthMC64b4fYl3mNsYSfrtlcnRVQ85kHKItOSVhYqa0gpB1TOVfQh2+MG?= =?us-ascii?Q?eqBcntdcUmot6vyaPSdDXXnfc7y1cFCiyvtrBji+gw9lPi7zb2IoHefAVgsh?= =?us-ascii?Q?U1hy2qphJK9SJtwv6b0mdotjeQRJsj23vcR/yrtUJ5A1GgiarC3kyCREnFQ4?= =?us-ascii?Q?iD8CQ5ZfRnhdrT+KieHISGPfMrMIxgfDNbiBCPn2vJRgjQ3G5UrGob/31ZCT?= =?us-ascii?Q?3GqkqOpMSGwkLP+TeJl5cRCbULYua8hQVxpCc5C14feyEFcR2in0jOvDO+dl?= =?us-ascii?Q?98LTGb07TAo5bzzRmSbilxadtgtwXiOBtR59BsP6Q+W+krGUnlNCJqLJas+M?= =?us-ascii?Q?c/TczgYUqDWUJS1CC5gysNAdKqmukrsWWqCcivPKC97ZvW6Ii1EQCmAw5l9X?= =?us-ascii?Q?vFVMoS/PGH3MgrdJxHfPVYz6P+0Cozl/4Z5dC69mG/e0HT/26LwV+znNMenJ?= =?us-ascii?Q?WEsz7bb7WSy98Z81wosL0Q9NEv1+ebKSCBuJ3av3nc9AQeXG8tBQr3iWqmgb?= =?us-ascii?Q?BQ/2DyBIj41QXSbm5OSQSuKZSFCVsCOoQ/hX+rWTFYyV9Z90NCGiyczNhGVf?= =?us-ascii?Q?N54QGbPa5lzQ8CN3r93vAI8WDqSP2U7w9fC9xakdTYAD/D5pUyyH9zRQAMj8?= =?us-ascii?Q?NTxMKYNneb+qg3MkxBzKFeNuGvLunI6WSaI5SFas?= X-MS-Exchange-CrossTenant-Network-Message-Id: e1f6f621-7b78-4ab1-f02f-08de1b85175a X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB5966.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Nov 2025 09:32:37.1919 (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: OG42L3W8bSBsX8br9DQAkAheK1Wkc+WX7p0wJdttH1L+b4gVzs8sTstww4d198ShnSDhfX8ES0BBT0L7z+xIkQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR11MB7942 X-OriginatorOrg: intel.com On Tue, Nov 04, 2025 at 04:40:44PM +0800, Xiaoyao Li wrote: > On 11/4/2025 3:06 PM, Yan Zhao wrote: > > Another nit: > > Remove the tdx_user_return_msr_update_cache() in the comment of __tdx_bringup(). > > > > Or could we just invoke tdx_user_return_msr_update_cache() in > > tdx_prepare_switch_to_guest()? > > No. It lacks the WRMSR operation to update the hardware value, which is the > key of this patch. As [1], I don't think the WRMSR operation to update the hardware value is necessary. The value will be updated to guest value soon any way if tdh_vp_enter() succeeds, or the hardware value remains to be the host value or the default value. But I think invoking tdx_user_return_msr_update_cache() in tdx_prepare_switch_to_guest() is better than in tdx_prepare_switch_to_host(). [1] https://lore.kernel.org/kvm/aQhJol0CvT6bNCJQ@yzhao56-desk.sh.intel.com/