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Thu, 26 Feb 2026 19:42:03 +0000 Date: Thu, 26 Feb 2026 11:42:02 -0800 From: "Luck, Tony" To: Peter Zijlstra CC: , , , , , , , , , , , , , Subject: Re: [RFC][PATCH 6/6] x86/resctrl: Fix SNC detection Message-ID: References: <20260226104909.675623579@infradead.org> <20260226105052.852170114@infradead.org> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260226105052.852170114@infradead.org> X-ClientProxiedBy: BYAPR05CA0058.namprd05.prod.outlook.com (2603:10b6:a03:74::35) 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_|DM3PPF3E6742BA8:EE_ X-MS-Office365-Filtering-Correlation-Id: 7657f0a5-8d94-44d9-d80a-08de756f1dc7 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|376014|7416014|1800799024|366016|7053199007; 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> } > > -/* CPU models that support MSR_RMID_SNC_CONFIG */ > -static const struct x86_cpu_id snc_cpu_ids[] __initconst = { > - X86_MATCH_VFM(INTEL_ICELAKE_X, 0), > - X86_MATCH_VFM(INTEL_SAPPHIRERAPIDS_X, 0), > - X86_MATCH_VFM(INTEL_EMERALDRAPIDS_X, 0), > - X86_MATCH_VFM(INTEL_GRANITERAPIDS_X, 0), > - X86_MATCH_VFM(INTEL_ATOM_CRESTMONT_X, 0), > - X86_MATCH_VFM(INTEL_ATOM_DARKMONT_X, 0), > - {} > -}; It isn't safe to drop this and the x86_match_cpu() check. These are the CPUs that implement SNC and MSR_RMID_SNC_CONFIG. So if you set __num_nodes_per_package > 1 on an older CoD system Linux will think this is SNC and poke this MSR (and get #GP). -Tony