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Peter Anvin" , "Peter Zijlstra (Intel)" , "Xin Li (Intel)" , Pawan Gupta , , , Mario Limonciello , "Gautham R. Shenoy" , Babu Moger , Suravee Suthikulpanit References: <20250818060435.2452-1-kprateek.nayak@amd.com> <20250819113447.GJaKRhVx6lBPUc6NMz@fat_crate.local> <20250820085935.GBaKWOd5Wk3plH0h1l@fat_crate.local> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20250820085935.GBaKWOd5Wk3plH0h1l@fat_crate.local> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Received-SPF: None (SATLEXMB03.amd.com: kprateek.nayak@amd.com does not designate permitted sender hosts) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF00020E64:EE_|LV9PR12MB9782:EE_ X-MS-Office365-Filtering-Correlation-Id: a609cd54-27b9-4684-155a-08dddfc9b250 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700013|7416014|376014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?QnhLYnJ4c21ub2luUk1xV1dURTh2NE5DelpZMmJMcXBPTzhwRy9SdnhNbEV2?= =?utf-8?B?bWNvYkFPODJkejlob2I0TWM2QkdHbzN3NUV0NE1BT1p3QXZWL0dsVk5pZDVJ?= =?utf-8?B?V2JsWGFLeHdzK0NRZTBJREJJS2hPU0F2RC9IUSttRm5vVGFGY0dDbFZOWVJk?= =?utf-8?B?N2lrMHYvVnI2ZFJmaEg0MjZnUEZJRS95ZTYrVjZSRGFNRXBuMGNaUW9BMXFx?= =?utf-8?B?aWJYaTRJeThuNkl5OWgyTVd6S1FaZlVvZ2pnTFMyS3lwSm4xQ2ZBUWM3WUg3?= =?utf-8?B?L1V6RzY3QXRjSXlVV2haNXlVTC9pRWFhSTdMaW5FeWd0NmRON1ZzWnJ2eXJU?= =?utf-8?B?a2pWc0loLzVCb1UwdklKNDFwUWFEYXZZdHBKM0dOVUN6R2xvbEI2NGg4WXVL?= =?utf-8?B?MmRFVjlDenRaSjJYNkpXRlZtczUxTjZEVGhwanpZaXNTZFZjZU55VXlaUGRo?= =?utf-8?B?WUVnZWMyV0NRWGJrS0pYdGVIZkUybkJGSkREaW13THF3SE1BN0NGYzMxTE1J?= =?utf-8?B?UTJURi8rMFJPVlJrQlVzSmg2NEpncjNGYUplRTZXZm9SbGhkZENQMTlLN0tl?= =?utf-8?B?d20rOTBFdVVTQ0EraUI2WlhNbWswQkZWNjJzWHBBNEFwM0VTMVBQVWFXcjRz?= =?utf-8?B?WWZyendHUUlER2dyQjAwTy8wYkdaczFMNXh0RlZ2Mk5VNGkvNm9VMEtnbkZP?= =?utf-8?B?UjlhVm95V2IycThqKzlpdTlFWGlsTHAxbm1XcU9GSE5YZDZSd0ZhRXhwdEU4?= =?utf-8?B?Q2tRTG5BOXhtUnBVU1ZUVjBHVWFXUnkrVi9VV3hBaVJXNTF3K25qdHZJYk9G?= =?utf-8?B?MkxnSENPcVp2UDNhTkUzUTdHTWcvTFhWeHV0K29IelhmcXQ5ZHZZM1lrc3lT?= =?utf-8?B?Zm9yeHRJcGtFNzdpYkRGN09nNC9ZSkdyRWxYcHhnWGtOTG1rN0RVL1VqYnpq?= =?utf-8?B?N0VrckNUQjFvQ3Q2MFlTcVV0SkkyZTZvak1jbjFNSHpuckx0dkFhdE5SVERh?= =?utf-8?B?U1JnbUQ2dHRUbFYrRng5ek5PdDE0eE9HdnkydmJoNmp4ZEZJUjFBZXdkVGhl?= =?utf-8?B?UDhtNlIrRmV6YjMvamlOcmxwVnNTRkVLdW1OOVdMcUlIOU1BTlVCWDN3d0NS?= =?utf-8?B?ZTVTME5zRDdDU0gxNURSbG9JMWkwRE8vY2UvY2hPVlVHM0FwZXhyZkNldDh4?= =?utf-8?B?dDJHT2l1QlFxZXJhNzdWaXZvTlBNelpKblFtQTBWeW41N215LzNMN2J2L2k0?= =?utf-8?B?L2dseTA4cTh5dGhCU1hKUGdKcW9kMVIyaVJYOUI3RFk1b0Y3OGlwRHBVSGFk?= =?utf-8?B?NTkxQnVKK0ZJVkU5TnVNdmdLVFFCaXdleEx0TTdsb1g3UVp6c29HU1YzZHdE?= =?utf-8?B?WEYvamNNaHd2VEFiSkcyU3Vac2U1UDBiVXZCaTMyWmIwR2ZHcVpaTHJTU2dO?= =?utf-8?B?ekZLd0xXd0tRYmJTTE5zSHhoNE41VUVxYkxvMnY4SCtJTUdudjRXV2d6K1RB?= =?utf-8?B?M1V5bjZTU0dnbTBoZUM3d1o5dnBIQXB0NlJqckJOcWpsS2pGRklPaUQyUmNG?= =?utf-8?B?MERsSTFEWk15SmNINzdXaUlOSVptU0pMYTUxTUl6cnU4czhzeVhlWUVCMTJG?= =?utf-8?B?UGVKWmhnMitJc3BTb2pXV3VmSWlDTkNaWWxqaXhEbFFGY21CQUFjaEFQNmxw?= =?utf-8?B?WjBUbG55N1dQYk9VM1pNRVJTaml4VUdXaUdhOVplQUpqY2JRQTJlRWNUcFQv?= =?utf-8?B?UklzTXYyaGduNUZjcGpHOWVHbEE4dVNDWk15djZIK3hEOHduTzB5ejZCMWtI?= =?utf-8?B?YjRqODB5VUZtd3NmYUw5b2VwMFZ3YVpUam9aUGdTUlVqdG9ieTA2QWc2VGlm?= =?utf-8?B?bzJYMHBvb1RmZUdrSUJabFJEZUQvdno0Wm9lVDROVCtuSkdCUzVGUnd4a0tj?= =?utf-8?B?TVUzZmdiSUR5dm9GMVI3ajdDV3ZUcnlDZksxajBrNTV4S1AvMk9mTThTRU43?= =?utf-8?B?QnJ5TWNJaEVlMGR2aWRWZUQwcHN0dFpSTVVmUzZXYm9VM3FZYTRWK1ZKaFBK?= =?utf-8?Q?eUGnWr?= X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB03.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(82310400026)(36860700013)(7416014)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Aug 2025 09:12:32.9053 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a609cd54-27b9-4684-155a-08dddfc9b250 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=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BL6PEPF00020E64.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV9PR12MB9782 Hello Boris, On 8/20/2025 2:29 PM, Borislav Petkov wrote: > On Wed, Aug 20, 2025 at 01:41:28PM +0530, Naveen N Rao wrote: >> That suggests use of leaf 0xb for the initial x2APIC ID especially >> during early init. I'm not sure why leaf 0x8000001e was preferred over >> leaf 0xb in commit c749ce393b8f ("x86/cpu: Use common topology code for >> AMD") though. > > Well, I see parse_topology_amd() calling cpu_parse_topology_ext() if you have > TOPOEXT - which all AMD hw does - which then does cpu_parse_topology_ext() and > that one tries 0x80000026 and then falls back to 0xb and *only* *then* to > 0x8000001e. > > So, it looks like it DTRT to me... But parse_8000_001e() then unconditionally overwrites the "initial_apicid" with the value in 0x8000001E EAX despite it being populated from cpu_parse_topology_ext(). The flow is as follows: parse_topology_amd() if (X86_FEATURE_TOPOEXT) /* True */ has_topoext = cpu_parse_topology_ext(); /* Populates "initial_apicid", returns True */ /* parse_8000_0008() is never called since has_topoext is true */ parse_8000_001e() if (!X86_FEATURE_TOPOEXT) /* False */ return; /* Proceeds here */ cpuid_leaf(0x8000001e, &leaf); tscan->c->topo.initial_apicid = leaf.ext_apic_id; /*** Overwritten here ***/ -- Thanks and Regards, Prateek