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Dadhania" Cc: linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, dave.hansen@linux.intel.com, pgonda@google.com, seanjc@google.com, pbonzini@redhat.com, francescolavra.fl@gmail.com References: <20250106124633.1418972-1-nikunj@amd.com> <20250106124633.1418972-6-nikunj@amd.com> <20250107104227.GEZ30FE1kUWP2ArRkD@fat_crate.local> <465c5636-d535-453b-b1ea-4610a0227715@amd.com> <20250107123711.GEZ30f9_OzOcJSF10o@fat_crate.local> From: Tom Lendacky In-Reply-To: <20250107123711.GEZ30f9_OzOcJSF10o@fat_crate.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SN7PR04CA0227.namprd04.prod.outlook.com (2603:10b6:806:127::22) To DM4PR12MB5070.namprd12.prod.outlook.com (2603:10b6:5:389::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR12MB5070:EE_|BY1PR12MB8448:EE_ X-MS-Office365-Filtering-Correlation-Id: 1e92bf36-1713-4004-972f-08dd2f4c92b3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|7416014|376014|1800799024; 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Dadhania wrote: >>>> + case CC_ATTR_GUEST_SNP_SECURE_TSC: >>>> + return (sev_status & MSR_AMD64_SEV_SNP_ENABLED) && >>> >>> This is new here? >> >> Yes, this was suggested by Tom here [1] > > Either of you care to explain why this is needed? > >>>> + (sev_status & MSR_AMD64_SNP_SECURE_TSC); > > I would strongly assume that whatever sets MSR_AMD64_SNP_SECURE_TSC will have > checked/set MSR_AMD64_SEV_SNP_ENABLED already. Yes, but from a readability point of view this makes it perfectly clear that Secure TSC is only for SNP guests. It's not on a fast path, so I don't think it hurts anything by having the extra check. But if you prefer the previous check, I'm ok with that. Thanks, Tom >