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Mon, 20 Jul 2026 10:03:58 +0000 Date: Mon, 20 Jul 2026 18:03:44 +0800 From: Chao Gao To: Jim Mattson CC: Sean Christopherson , Reinette Chatre , , , , , , , , , , , , Yosry Ahmed Subject: Re: VMX Preemption Timer appears to be buggy on SKX, CLX, and ICX Message-ID: References: Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: SI1PR02CA0052.apcprd02.prod.outlook.com (2603:1096:4:1f5::20) To CH2PR11MB4456.namprd11.prod.outlook.com (2603:10b6:610:48::22) Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BY5PR11MB4450:EE_|CO1PR11MB5073:EE_ X-MS-Office365-Filtering-Correlation-Id: 5f97cea9-b083-4d14-4699-08dee64635fe X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016|23010399003|18002099003|22082099003|10067099003|4143699003|56012099006|11063799006; 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It sounds like you are >> >saying that the exponent may depend on IA32_VMX_MISC[4:0]. >> >> Let me double-check this with the internal team and get back to you. > >Have you discovered anything? I just got the final answer: 2^25*M/N is the max value of VMX preemption timer for _all_ affected processors. Our expectation is that for processors that have different value it will have the issue fixed (VMX preemption timer will implement full 32-bit). Use of 2^25*M/N will still be fine. where M is CPUID.15H:EBX[31:0] and N is CPUID.15H:EAX[31:0].