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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by CY4PEPF0000EE36.mail.protection.outlook.com (10.167.242.42) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8398.14 via Frontend Transport; Wed, 5 Feb 2025 10:14:07 +0000 Received: from [10.136.39.79] (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Wed, 5 Feb 2025 04:14:02 -0600 Message-ID: <0835864f-6dc5-430d-91c0-b5605007d9d2@amd.com> Date: Wed, 5 Feb 2025 15:43:54 +0530 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] sched/topology: Enable topology_span_sane check only for debug builds To: Peter Zijlstra CC: Naman Jain , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , , , Steve Wahl , Saurabh Singh Sengar , , Michael Kelley References: <20250203114738.3109-1-namjain@linux.microsoft.com> <20250205095506.GB7145@noisy.programming.kicks-ass.net> Content-Language: en-US From: K Prateek Nayak In-Reply-To: <20250205095506.GB7145@noisy.programming.kicks-ass.net> Content-Type: text/plain; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Feb 2025 10:14:07.4324 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d954e301-97db-44a1-b6bf-08dd45cdd388 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CY4PEPF0000EE36.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB5594 Hello Peter, Thank you for the background! On 2/5/2025 3:25 PM, Peter Zijlstra wrote: > On Wed, Feb 05, 2025 at 03:18:24PM +0530, K Prateek Nayak wrote: > >> Have there been any reports on an x86 system / VM where >> topology_span_sane() was tripped? > > At the very least Intel SNC 'feature' tripped it at some point. They > figured it made sense to have the LLC span two nodes. > > But I think there were some really dodgy VMs too. > > But yeah, its not been often. But basically dodgy BIOS/VM data can mess > up things badly enough for it to trip. Has it ever happened without tripping the topology_sane() check first on the x86 side? -- Thanks and Regards, Prateek