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Tue, 18 Aug 2026 00:51:28 +0000 Message-ID: Date: Mon, 17 Aug 2026 17:51:27 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 04/17] x86/resctrl: Honor rdt=perf option to force enable AET perf events To: Tony Luck , Fenghua Yu , "Maciej Wieczor-Retman" , Peter Newman , James Morse , Babu Moger , Drew Fustini , Dave Martin , Chen Yu , David E Box , CC: Christoph Hellwig , , References: <20260729172752.11561-1-tony.luck@intel.com> <20260729172752.11561-5-tony.luck@intel.com> Content-Language: en-US From: Reinette Chatre In-Reply-To: <20260729172752.11561-5-tony.luck@intel.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4P222CA0008.NAMP222.PROD.OUTLOOK.COM (2603:10b6:303:114::13) To SJ2PR11MB8370.namprd11.prod.outlook.com (2603:10b6:a03:540::20) 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: SJ2PR11MB8370:EE_|SA7PR11MB9544:EE_ X-MS-Office365-Filtering-Correlation-Id: 6dcab3f3-3b8f-487a-ea0a-08defcc2d686 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024|7416014|23010399003|921020|6133799003|18002099003|22082099003|4143699003|11063799006|56012099006|10067099003|3023799007; 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The > "rdt=" kernel command line option lets the user override ("force_on") when > a feature is disabled in such case. Users may also disable ("force_off") > individual supported resctrl features they do not need. > > Linux enumerates AET once on first mount and skips this enumeration if > the associated event group is supported but disabled. Since AET is only > enumerated once, this check is guaranteed to only consider disabling via > the rdt= kernel parameter. > > However, when transitioning to enumerate AET on every mount, it is no longer > correct to skip enumeration simply because an event group is marked as > disabled. It is then possible for resctrl to have force-disabled the event > group during an earlier enumeration due to insufficient RMIDs, which would > improperly cause the kernel to ignore a user's explicit rdt= override on > subsequent mounts. > > Ensure the user's command line choices take precedence over system-level limits. > > Signed-off-by: Tony Luck > --- Reviewed-by: Reinette Chatre Reinette