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Peter Anvin" , Maxim Levitsky , , , Matteo Rizzo , References: <20251101000241.3764458-1-jmattson@google.com> <6f749888-28ef-419b-bc0a-5a82b6b58787@amd.com> Content-Language: en-US From: Shivansh Dhiman In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS3PEPF000099E2:EE_|IA1PR12MB6067:EE_ X-MS-Office365-Filtering-Correlation-Id: f0ce7f5a-5e4f-473f-734f-08de1dcb92ec X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|7416014|376014|36860700013|1800799024; X-Microsoft-Antispam-Message-Info: =?utf-8?B?bHVpaXh4V1FrUVIrdlVXaW9tQk1KMGxCTnJoblY1VExuTU01bjgzdHF2b0hl?= =?utf-8?B?Z1haaGxCd283Z0UwbzlVM1NIOTNuZkNzZ0xqRjRMVjlmVDNoMVFGTDZCRHRk?= =?utf-8?B?UHVHM2ovc2xQZ1AwSmxXbHZlSFlrTTFlQkFIWFVGSFhZY0NBa2tIKytSN2lj?= =?utf-8?B?MGloN3h6TGlTOS9hL0pZZjh4NWJEN1Y0Mmk1a1RvaWFCM1Uxc0JHTXJaTEZK?= =?utf-8?B?cVF3QUYyZit2QjJKMVpxTXV6Y2FUMEpGVW4rZmtia0JRTk5RbTlMTmpVZ2d5?= =?utf-8?B?a3N1bkVIeCtWSFIvSHp3TXJLNGEvU0pZR3dMRDZuMGFxNkdFOU5LTm1vREpI?= =?utf-8?B?cXp4SkpZZWdNUnZ4L1hFWEtuL0s1dFE5NHZPMENUMlNYeGNtTWJoR3R3WUZP?= =?utf-8?B?cDVHamF1SzM2amU2eDQzY0lDT3JEZHdxZHlTYmlMTjB4ZlRDTkZ1M3Urc2lN?= =?utf-8?B?UGxwVVo2dzlIWkZmN0JlNGlxanowSFVmYkFpcmVYTmJvMk9zVnl6a2V2QTRm?= =?utf-8?B?VjBIaE1NcHg3MTBuVDNXRUk3MlIrWUd1TzcyWWVlSnRleEtubDdjOGY3dU9D?= =?utf-8?B?dENMWjVueEo2UzBiWGJUUExabjFjY0dFYU5iRXU5ZHVjVmg4SnBaejFuNkRW?= =?utf-8?B?dnFnVy9ieVk4UU9kQk9wMmFxOU10dEtJQUdrUDdLc2xuTVpjQlBhSUtCZ1Fk?= =?utf-8?B?TXVWR25jaXZGeWJwSVgwYmtVTURRc3A4RkNBeVdxWFM1SFR6a3BIM1Q5Mkhs?= =?utf-8?B?TkN6ODBaQWF0cnpyY2FkZFVGdmI2TFU1bDdoejlPY014dUNlZHNQQlZHcUdv?= =?utf-8?B?Vkh0bjlzY2lJa1hsRnNpR2VCKzR6N1hhMzZQWDhDdzg4S3ZObE9pc3lWaTRR?= =?utf-8?B?OWMybEJUemg2YS9hQkp2VFg1dWdzM3Y5N3Z5anJPM1F4bGlNZVM3UFQyQVh5?= =?utf-8?B?Y25nT3VMOVhRYzI2RjJNTDZuNTBKQnFjQkdTTTVCVkZLbTM4R293RUFTNk5a?= =?utf-8?B?bVJEckVyNFp0cmNIZkJsSXFLZGlVSm0zbk5SWDdwYVZvMzhoOGhMY0RsRGtp?= =?utf-8?B?ZHRCTWVWTlVRN3V2REVjMjVieU42UVZVVlVCcHRlbzY1WjBvRVdjU2NjQkFR?= =?utf-8?B?b3I0RVlITVNEdUs3dWlXNi9TVVVuNVRpSll3QlkyTGpNY1A3TjNSbU5KTnBu?= =?utf-8?B?MmoxL0hJQ0YyWGM3UkFnK2twZnF2ZTlHY09iclI4VDl1SWVIUDA2V0xjbnlL?= =?utf-8?B?emMrUkJ5Zy9SdW1aVWExSGljYjhieWlkbzRhR2J2VEhMaGRkVmxhaGVVZnhL?= =?utf-8?B?NytudGJac0JBT0E4djFIRUZzZkFZZmJyajFCSzF3UXB1SVNoQkZLaDI1Skxj?= =?utf-8?B?eTJoRFd3dlJDcHFqWWlqcUhVZjN6YS9GVnFxdnR0UENWbDFvV3A4a1NqYmdU?= =?utf-8?B?T3ZoOWI2ZWl1Um5mdExoRG9ub2JjNXUzaHMvYWIvNGZ6ak1NekVhUnkxSzU5?= =?utf-8?B?YTFIcCtVOTZLaVA3dWFFMGNtSVUvcnc2RlVNY25LWnVlVlJZc2VQK3dralhF?= =?utf-8?B?TVpoKzdhTzl3SzdvK0h5eVVaRUw5WGJTOWVFSkpQZERDRkZvVVdCeVJMNHYx?= =?utf-8?B?dHpKNitoUlI5ZlplYmZUQWdyTUwrOVc5RlA1VDNDa1gvbHg3SEh6ekZKMGdD?= =?utf-8?B?MDMxR3pCeHFCbkNOb1FERVVGTGdPTXFuV0cxK08vek5ZUGsyN3pQZ1BadFlC?= =?utf-8?B?NnBaMVlRZ2YvQi9NVWVZcWl2SkpMTmdwUkJsQVlhcXhOMXdwRlpUeFVtSDV6?= =?utf-8?B?WUkrSDZHcXZ3dkdlSTIvbFlnajF5eElzeWhETXhRU3BlZEczVjJqQXZabDBX?= =?utf-8?B?WUs3RmRVd2RCanhteERmS0tPRzl4QXQ3MHBxcFd0ODVwTU9QeXBqRk50VEgz?= =?utf-8?B?S3RlVm5WaEJwWkU5cTQvdG1XVWoveEZnaS81TG1GUDJIaitzY0h5Y1hkbHp6?= =?utf-8?B?RkxTSEMyRlBwZE1RNWFFaDBtYzZWL2l2THMvYStXdGI5UTQyMWQvTXUwcGFn?= =?utf-8?B?cEZlMGVLM3V3VEZ2elEwdUowWWdCQXdUZkZTM0VVenVSWTVvbDlYalpBb2FF?= =?utf-8?Q?Aq8U=3D?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(82310400026)(7416014)(376014)(36860700013)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Nov 2025 07:02:11.2936 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: f0ce7f5a-5e4f-473f-734f-08de1dcb92ec X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS3PEPF000099E2.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6067 On 06-11-2025 23:30, Jim Mattson wrote: > On Thu, Nov 6, 2025 at 8:09 AM Shivansh Dhiman wrote: >> >> On 01-11-2025 05:32, Jim Mattson wrote: >>> With the VMCB's LBR_VIRTUALIZATION_ENABLE bit set, the CPU will load >>> the DebugCtl MSR from the VMCB's DBGCTL field at VMRUN. To ensure that >>> it does not load a stale cached value, clear the VMCB's LBR clean bit >>> when L1 is running and bit 0 (LBR) of the DBGCTL field is changed from >>> 0 to 1. (Note that this is already handled correctly when L2 is >>> running.) >>> >> Hi Jim, >> I am thinking, is it possible to add a test in KVM Unit Tests that >> covers this? Something where the stale cached value is loaded instead of >> the correct one, without your patch. > > Though permitted by the architectural specification, I don't know if > there is any hardware that caches the DBGCTL field when LBR > virtualization is disabled. Alrighty. Tested-by: Shivansh Dhiman -Shivansh