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Wysocki" , Viresh Kumar References: <20260716-amd-pstate-vm-v1-1-2ac97d3cf6e7@rong.moe> <0c55d331-bf98-4e6e-9de5-35803ead3c0a@amd.com> <20260715180454.GAalfLxn3Wyu-fRjoT@fat_crate.local> <61a141cd-c72a-4ee5-8273-ee721aa13f68@amd.com> From: Mario Limonciello In-Reply-To: <61a141cd-c72a-4ee5-8273-ee721aa13f68@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: BN0PR07CA0027.namprd07.prod.outlook.com (2603:10b6:408:141::29) To PH8PR12MB6914.namprd12.prod.outlook.com (2603:10b6:510:1cb::21) Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR12MB6914:EE_|SA0PR12MB4494:EE_ X-MS-Office365-Filtering-Correlation-Id: 08809f7f-9adc-4d7c-f14f-08dee2b34584 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|376014|1800799024|366016|11063799006|10067099003|6133799003|22082099003|18002099003|4143699003|56012099006; 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I meant CPU model. >> >> I usually boot a KVM with `qemu-system-x86_64 -accel kvm -cpu host >> ' to test various patches. These messages is a bit >> disturbing to me as they are KERN_WARNING messages. >> >> FYI, my device is Zen 5 based and always triggers both messages. >> >> I can also reproduce both messages with `-cpu EPYC-Genoa' and `-cpu >> EPYC-Turin'. It's just due to how amd_cppc_supported() is implemented. >> >>> but we won't patch the upstream kernel just because it >>> dumped an error message in the guest. >> >> Well, the reason why I decided to send this is not only about how noisy >> it is, but also about the correctness. >> >> The first messages says: >> >>     The CPPC feature is supported but currently disabled by the BIOS. >>     Please enable it if your BIOS has the CPPC option. >> >> The CPPC feature is neither supported in a KVM nor disabled by the VM's >> BIOS. >> >> IIUC, it's disabled by kvm_cpu_cap_init(CPUID_8000_0008_EBX, ...), so >> the upstream kernel both disables it as a hypervisor and warns about it >> as a guest. What a paradox! >> >> At least the first message is nonsense in this case and the paradox >> should really be fixed. If you prefer preserving the second message >> ("the _CPC object is not present in SBIOS or ACPI disabled") as an >> informative hint anyway, how about moving the virtualization check into >> amd_cppc_supported() to only mute the first one? ;-) > > I think changing amd_cppc_supported() to return false for > X86_FEATURE_HYPERVISOR makes sense and can remove the message.  The > heuristic there doesn't seem relevant when virtualized. > > With Xen, the Xen hypervisor itself controls CPPC.  dom0 > (xen_initial_domain()) doesn't need the amd-pstate driver. > > Regards, > Jason OK, Rong - please send an updated patch.