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Wysocki" , Viresh Kumar , Borislav Petkov , Jason Andryuk CC: Michael Kelley , Michael Kelley , , References: <20260721-amd-pstate-vm-v3-1-8b59574fb714@rong.moe> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20260721-amd-pstate-vm-v3-1-8b59574fb714@rong.moe> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS2PEPF00003442:EE_|DS5PPFB297DAF97:EE_ X-MS-Office365-Filtering-Correlation-Id: 53e7dcf9-0685-4b0a-f743-08dee6e74084 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|23010399003|82310400026|32650700020|36860700016|6133799003|18002099003|22082099003|56012099006|11063799006|10067099003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(376014)(23010399003)(82310400026)(32650700020)(36860700016)(6133799003)(18002099003)(22082099003)(56012099006)(11063799006)(10067099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: +GK0ekI1Ux5S+Wsznwn8syFQbRXaRuGcTzMXeJ7v68jFyO30wXV6zwucgudOn3Ok04G7+PQejbnKpYGRG4Fdw8ZlAkT/DBs3cy1EKgKZP/TfbY7MF6Kz7vkKigLUYHYThT0JJ2Gp1gWy5UkJMt6IWp9afxnNxEqX21SWn3627lgQnL+X+DJa+1RCIc8ZpdsbBBC0AsyaUKcmSgCjfjnIawA2CFE3isCRJL65Mgye+Jp3G+P7F1EjNIfVRkjt0mbOG0lhdoYUv9Y3cpRFlCyFIP/s/2amPesAHSI3q8POek7OBHSKoRvl1/TRHxOqgptMDVPm7qKQQBk96+OQvu8utNFSsHnqY22zn6OWfxFduYxjxwiAlzc7743mOXHu1a1vRlXjtzi6vIrUUTQ4HCBfB9UEDPj1oZxEAb8qIgItmYFaPQ7oIadNA5roh+FFlKgX X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Jul 2026 05:16:42.6666 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 53e7dcf9-0685-4b0a-f743-08dee6e74084 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: DS2PEPF00003442.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS5PPFB297DAF97 Hello Rong, On 7/21/2026 12:17 AM, Rong Zhang wrote: > When booting a VM that simulates or passes-through a relatively new CPU > model, these warning messages are printed to kmsg: > > amd_pstate: The CPPC feature is supported but currently disabled by the BIOS. > Please enable it if your BIOS has the CPPC option. > amd_pstate: the _CPC object is not present in SBIOS or ACPI disabled > > Technically the check is not wrong and acts as a safetynet that prevents > the driver from being registered incorrectly, but the warning messages > are noisy and incorrect, as the CPPC feature is neither supported in a > VM nor disabled by the VM's BIOS. > > The CPPC feature is disabled by the hypervisor as it makes no sense to > expose them to guests. It creates a paradox that the same kernel both > disables CPPC as a hypervisor (KVM) and warns about it being disabled > as a guest. > > X86_FEATURE_HW_PSTATE indicates if the processor supports frequency > scaling or not. It is disabled on virtualized platforms (namely, KVM and > Hyper-V have been reported to do so) and is always set on physical > platforms that support frequency scaling. > > Check for X86_FEATURE_HW_PSTATE as a prerequisite and bail out early if > it's unsupported. A debug message is also added to help debug driver > loading issues. > > Fixes: cb817ec6673b ("cpufreq: amd-pstate: show CPPC debug message if CPPC is not supported") > Reviewed-by: Michael Kelley > Tested-by: Michael Kelley > Signed-off-by: Rong Zhang Thank you for your patience! Feel free to include: Reviewed-by: K Prateek Nayak Tested-by: K Prateek Nayak -- Thanks and Regards, Prateek