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Thu, 10 Jul 2025 08:00:59 +0000 Message-ID: <292e70ed-aae5-4f52-8f85-80cba7ff301d@intel.com> Date: Thu, 10 Jul 2025 16:00:46 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [tip:sched/core] [sched/smp] 06ddd17521: BUG:using_smp_processor_id()in_preemptible To: Sebastian Andrzej Siewior CC: kernel test robot , Ingo Molnar , , , , , Peter Zijlstra , Dietmar Eggemann , Juri Lelli , "Linus Torvalds" , Mel Gorman , Shrikanth Hegde , Steven Rostedt , Valentin Schneider , "Vincent Guittot" , References: <202507100448.6b88d6f1-lkp@intel.com> <6cf071f3-ff5b-4025-8ce7-2f2cceb03984@intel.com> <20250710062528.T-Obm39T@linutronix.de> Content-Language: en-US From: "Chen, Yu C" In-Reply-To: <20250710062528.T-Obm39T@linutronix.de> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SG2PR06CA0242.apcprd06.prod.outlook.com (2603:1096:4:ac::26) To DM4PR11MB6020.namprd11.prod.outlook.com (2603:10b6:8:61::19) 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: DM4PR11MB6020:EE_|IA1PR11MB6289:EE_ X-MS-Office365-Filtering-Correlation-Id: 0ca5a193-67dc-43f2-20d8-08ddbf87e7c7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|1800799024; 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If you look closely you will see that the call chains > is > vmx_init() -> kvm_is_vmx_supported() -> __kvm_is_vmx_supported() > > There is a migrate_disable() around __kvm_is_vmx_supported(). So why > does this warning trigger then? > migrate_disable() disables the task migration between CPUs by restricting the task's affinity, but it does not disable the preemption on single CPUs IMO. The scope of guard(preempt)() in migrate_disable() is just within the migrate_disable(). debug_smp_processor_id() warns when the preemption is enabled. Thanks, Chenyu