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Tue, 14 Apr 2026 22:22:24 +0000 Date: Tue, 14 Apr 2026 15:22:23 -0700 From: "Luck, Tony" To: Borislav Petkov CC: "Zhuo, Qiuxu" , "Li,Rongqing(ACG CCN)" , Nikolay Borisov , "Thomas Gleixner" , Ingo Molnar , Dave Hansen , "x86@kernel.org" , "H . Peter Anvin" , Yazen Ghannam , Avadhut Naik , "linux-kernel@vger.kernel.org" , "linux-edac@vger.kernel.org" Subject: Re: [PATCH] x86/mce: Restore MCA polling interval halving Message-ID: References: <20260210150117.GBaYtIPfsP0Txw7iIc@fat_crate.local> <3748e8c7057a4182bc2a361b44dda51b@baidu.com> <3431b52760444d209f8460059264cc13@baidu.com> <20260306152903.GEaaryvxD9BTT7Fd10@fat_crate.local> <20260316134411.GBabgJK1RFUG3zrTrx@fat_crate.local> <20260406224915.GAadQ4azQ7IRsTjnXD@fat_crate.local> <20260414211803.GFad6vC9LSYxGScTNH@fat_crate.local> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260414211803.GFad6vC9LSYxGScTNH@fat_crate.local> X-ClientProxiedBy: BYAPR05CA0086.namprd05.prod.outlook.com (2603:10b6:a03:e0::27) To SJ1PR11MB6083.namprd11.prod.outlook.com (2603:10b6:a03:48a::9) 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: SJ1PR11MB6083:EE_|SA3PR11MB9485:EE_ X-MS-Office365-Filtering-Correlation-Id: f06fd2e8-3a3e-4343-9f53-08de9a744dc6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|22082099003|18002099003|56012099003; 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But the following code in mce_notify_irq() is now > > never executed, and I didn't see the error log message "Machine check events logged". > > You did disable the CEC, right? > > In any case, let's have a look: > > When we log an MCE, we do: > > mce_log # add it to the genpool and run the works > -> mce_irq_work > -> mce_schedule_work > -> .. > -> mce_gen_pool_process # this'll send it down the notifier chain > -> x86_mce_decoder_chain > -> mce_early_notifier # that guy sees it here and issues the trace record > > Now, mce_notify_irq() would do mce_work_trigger() and issue the printk > - dunno, I guess we still want our printk and probably should add it back > - but the first one - the work triggering - that's mcelog. It is using that > usermode helper gunk, dunno if you guys still need it. > > Because mcelog does register to the decoder chain so it'll get to see the MCE > eventually. So that part is fine. > > The only question is the usermode helper gunk... > > Tony? Ran my own test. RAS_CEC disabled. Booted with mce=no_cmci injected a corrected error every twenty seconds. Added pr_info() to mce_timer_fn() to say which CPUs were doubling or halving interval. Results: I did see some "Machine check events logged" console messages. The debug messages are "interesting". Polling timers on CPUs aren't synchronized, so I got random bursts of debug messages where some CPUs found an error and halved their interval, while others didn't see an error and doubled their interval. The machine check banks for memory corrected errors are socket scoped, so when an error is logged whichever CPU on the socket polls next will find the error. Both mcelog and EDAC were invoked on the mce decode chain and logged errors OK. When I stopped injecting, all the CPUs doubled back up to maximum polling interval. Summary: This is working as well as can be expected given the shared scope of the machine check banks. If Linux were to understand the scope of machine check banks it might designate a single CPU in that scope to do the polling. But Intel doesn't make it easy to derive the scope. In any case, the common case is CMCI enabled. -Tony