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Shenoy" To: K Prateek Nayak Cc: Borislav Petkov , Naveen N Rao , Thomas Gleixner , Ingo Molnar , Dave Hansen , Sean Christopherson , Paolo Bonzini , x86@kernel.org, Sairaj Kodilkar , "H. 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?YaAr5+9CeWZVVT5+wNGLwV35peI53nFSy9C0w0jMhLo04xLanFkgaM5cea0+?= =?us-ascii?Q?nenHaqUou5dkSqHoMVwsvcnDB3dEg2hfjzo8AoYoJ31ftOv6k5RFO7QDQ+kD?= =?us-ascii?Q?rgxITOdBgWN8ek0PShVeJxgCGJfgS67uY47D0m0YUF8eaoM2gxrVMkMKBqRB?= =?us-ascii?Q?VziGcuBobEUd/vvfy0p7tgtL+nOJB8q9C6T7OM09Y63Fn2vUFPgfe0kk3iNp?= =?us-ascii?Q?+pLSttMOqIyhYTwvD4yl1u8+iEyEbfcYct5UKcgkMnXV2Af1MjU4qVuEu0mS?= =?us-ascii?Q?f6OkJaEmGuvO6Oe9mHK/wco72xAcyOmL7EkhjX8Iym76obknXJdYP4Jf+hio?= =?us-ascii?Q?9VT02doQDy3rUMHRzPpO5VLgkuDdmIfsY7EsFDh83LhJBdxYA89U2sgzZpI5?= =?us-ascii?Q?k5u0cUIButA6xWkUnmwiYUZdNJRcEF92Zmc+DYEN5rzsnaIu+Ye/QD5bmQHU?= =?us-ascii?Q?IeLltuKPITmQurF/NjwbAYgKeoRvNYOpKzs65opI3mWc8gjwBKL4EAVdvTsB?= =?us-ascii?Q?ZGYcNrvsH47xp24HhLPSwbu64ajHeyeKOPMqCF0FH88qAH+lWAgNvkaInsB8?= =?us-ascii?Q?5S1DcRObE25bI3ZvV8WYtGHjQ/l3Rzceo82hB4jVVjr1dxsLre2rD6WYUfUM?= =?us-ascii?Q?3RlL+I7PFR/o3q9V7g8r6g6ADqHvvK3D5sjzLpAPv7Bigt+m8w9yvJ3n0AIS?= =?us-ascii?Q?2bDvwEFmtT3HTtE5pJZoc1qV+OtUCIsf2GZwNf29lI0b1LAkBT4YeKfeS6r5?= =?us-ascii?Q?mxdrGkxAIP2Wisnu0FbXlvAzIYXZzsnEx6NFvc5LlQE2tlVrkiCGUmzhUXS1?= =?us-ascii?Q?t+lUqHUeaHP0UWCV+ASz88MMCeo2A4VR1mtNzZkfgDi1gXCA2iBsg3U61NsZ?= =?us-ascii?Q?VV+iLoAUpz6nPjaAgb0XqRtNwYVCGeQNOHGZRjI4BI6tsTHA1U1bjPF+CGg2?= =?us-ascii?Q?0a+iChHqwrLa+kZO+0r1GE4gMjon+1njeYxy39XliA54pUxz3USHtQLX9EuQ?= =?us-ascii?Q?6W+Xb4WxC2xqK+63s0gsgPH+dfXqw6Fo8joRMv9X55wLgUDQ+lK/v9cpi1Kv?= =?us-ascii?Q?YSf1V8jCaetlJS2ss3RncX8xTPtj7DvpZWrNJUj6o5QKQn9Y/vcQfs0Iy2dE?= =?us-ascii?Q?a6UnNrQEGTfyJAYuRCqIFYpeRWSMc3NlQUw41O2oVMdaeo+HP/29ugQ2CkpE?= =?us-ascii?Q?gKtvXiW1PFgpYK5+pKKadBKrTM7g6znUI81GYzxXZe8yzVJdMwkGZsnIEr8Y?= =?us-ascii?Q?sOm4PE9H7J0eul51HAN8Yy/ZKbxDGyWOZappdkrHNLmLr94O/KfddKWSWx0g?= =?us-ascii?Q?gh2LRFgimKcSDDqZhvRQCmg95iqN02Syti255Uq+YriFn2Q2NFEeXgV4R16N?= =?us-ascii?Q?75VxyoLjmY655LzvbKDLANy87LTjKyJOc3COYn42q2hb9vNXYq2rN/qlwp83?= =?us-ascii?Q?f3F4ydewcZP1jU2Asf+s9pC2tbN6xC/eMrBtqUHgmwow73+RjkAEiIDTLqdx?= =?us-ascii?Q?nvsYWICwyyDSOzYgMxwBw0+4xtqewJbtENQUU2i7qdVbI+/sTreVqkzGSYf9?= =?us-ascii?Q?cb2mKQFmhj3d+UL7erXyYAiX+WeyPhC+K1XMBsqV?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 93a43bc9-c437-4a6a-0383-08dddfd0395e X-MS-Exchange-CrossTenant-AuthSource: CY8PR12MB8243.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Aug 2025 09:59:17.2238 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: qX7Y7W/rwSdIo48z7eIsF2xDbpUBASqD0p9axm6t8Qj/t40CgyOoIQNdyHNk4jwCVU34mh4pB/4Z8IJI7n4yqQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB8106 On Wed, Aug 20, 2025 at 02:42:26PM +0530, K Prateek Nayak wrote: > 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 */ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > cpu_parse_topology_ext(); Patch 2 from this patchset, which removes this "if" condition above seems to be the right thing to do. X86_FEATURE_TOPOEXT refers to CPUID 0x80000001.ECX[22] which advertises the support for 0x8000001D.EAX and 0x8000001E.EAX. OTOH, the function cpu_parse_topology_ext() parses the topology via the following CPUIDs in that order * CPUID 0x1f (Intel Only) * CPUID 0x80000026 (AMD only) * CPUID 0xB (Both Intel and AMD) None of these have anything to do with X86_FEATURE_TOPOEXT. So the call to cpu_parse_topology_ext() in parse_topology_amd() doesn't have to be gated by the presence or absence of X86_FEATURE_TOPOEXT. I agree that QEMU needs to sort out what needs to do something better than clearing all the regs of CPUID 0x8000001E on encountering a topology with more than 256 cores. Or at the very least not clear the CPUID 0x8000001E.EAX which has the provision to advertise a valid Extended APIC ID. -- Thanks and Regards gautham.