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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by CO1PEPF00012E62.mail.protection.outlook.com (10.167.249.71) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.181.6 via Frontend Transport; Wed, 8 Jul 2026 04:55:00 +0000 Received: from satlexmb10.amd.com (10.181.42.219) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.41; Tue, 7 Jul 2026 23:55:00 -0500 Received: from satlexmb08.amd.com (10.181.42.217) by satlexmb10.amd.com (10.181.42.219) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.41; Tue, 7 Jul 2026 23:54:59 -0500 Received: from [10.252.210.85] (10.180.168.240) by satlexmb08.amd.com (10.181.42.217) with Microsoft SMTP Server id 15.2.2562.41 via Frontend Transport; Tue, 7 Jul 2026 23:54:49 -0500 Message-ID: <42708d69-42ff-48ec-bd54-0e683c440ae8@amd.com> Date: Wed, 8 Jul 2026 10:24:43 +0530 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 06/51] x86/sev: Don't override CPU frequency calibration for SNP's Secure TSC To: Sean Christopherson , Jonathan Corbet , Paolo Bonzini , Thomas Gleixner , "Ingo Molnar" , Borislav Petkov , Dave Hansen , , Kiryl Shutsemau , Rick Edgecombe , "K. Y. Srinivasan" , Haiyang Zhang , "Wei Liu" , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , "Andy Lutomirski" , Peter Zijlstra , Juergen Gross , Daniel Lezcano , John Stultz CC: Shuah Khan , "H. Peter Anvin" , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , , , , , , , , Tom Lendacky , David Woodhouse , David Woodhouse , Michael Kelley , Thomas Gleixner References: <20260701193212.749551-1-seanjc@google.com> <20260701193212.749551-7-seanjc@google.com> Content-Language: en-US From: "Nikunj A. Dadhania" In-Reply-To: <20260701193212.749551-7-seanjc@google.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF00012E62:EE_|DM4PR12MB6135:EE_ X-MS-Office365-Filtering-Correlation-Id: 162212d4-dfcb-4a25-3888-08dedcad1125 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|32650700020|23010399003|7416014|82310400026|376014|36860700016|6133799003|921020|3023799007|18002099003|22082099003|4143699003|11063799006|56012099006; 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)(32650700020)(23010399003)(7416014)(82310400026)(376014)(36860700016)(6133799003)(921020)(3023799007)(18002099003)(22082099003)(4143699003)(11063799006)(56012099006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: k/vu6e0T2XlctZLtJdyr6MexpXA2QcnV3xEzcFHJPOr/EVdlmu5jyyjU3hTpkaj5sh8Q2y3b/oi2T6yg5BS4I2gkl3iwOY4W8YI0JYQn4qaUozlGtxruJH8ND67IXFH5zEGYOYaV/0OXdww5VFZi13//IA5WtOyUwh16xmnxbaWAEukUp8EMHCFs/m2RgKsJ02i5bbFAOJLM3+63L9EcgZBkAwu92lj4C3kZfQh3fSf2EYP4LTnxGc6551h1t5bca8bJI7bILyDm8jjXR3zGD7CVA5v4AF2ZpRuiFHauy3oxqkmM2IaFsrtWN/Gkal6K/iafbEZoOVceprE2xzZiQ0ePte4wrSzkYgnG5cHDAtbS8ilBBRfKoJ6rfSUH3DkVcnHHqNZNReQnzrp4rohh+VZI4K75igXJuV9+fqIV5LaVkRY69kxkt1NWz8UA5DQz X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jul 2026 04:55:00.6860 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 162212d4-dfcb-4a25-3888-08dedcad1125 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: CO1PEPF00012E62.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6135 On 7/2/2026 1:01 AM, Sean Christopherson wrote: > Don't override the kernel's CPU frequency calibration routine when > registering SNP's Secure TSC calibration routine. SNP (the architecture) > provides zero guarantees that the CPU runs at the same frequency as the > TSC. The justification for clobbering the CPU routine was: > > Since the difference between CPU base and TSC frequency does not apply > in this case, the same callback is being used. > > but that's simply not true. E.g. if APERF/MPERF is exposed to the VM, then > the CPU frequency absolutely does matter. > > While relying on heuristics and/or the untrusted hypervisor to provide the > CPU frequency isn't ideal, it's at least not outright wrong. > > Fixes: 73bbf3b0fbba ("x86/tsc: Init the TSC for Secure TSC guests") > Cc: Nikunj A Dadhania > Cc: Tom Lendacky > Signed-off-by: Sean Christopherson Reviewed-by: Nikunj A Dadhania > --- > arch/x86/coco/sev/core.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c > index ed0ac52a765e..665de1aea0ee 100644 > --- a/arch/x86/coco/sev/core.c > +++ b/arch/x86/coco/sev/core.c > @@ -2046,7 +2046,6 @@ void __init snp_secure_tsc_init(void) > > snp_tsc_freq_khz = SNP_SCALE_TSC_FREQ(tsc_freq_mhz * 1000, secrets->tsc_factor); > > - x86_platform.calibrate_cpu = securetsc_get_tsc_khz; > x86_platform.calibrate_tsc = securetsc_get_tsc_khz; > > early_memunmap(mem, PAGE_SIZE);