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Peter Anvin" , Ravi Bangoria , Ananth Narayan , "Sandipan Das" Subject: [PATCH] perf/x86/amd/core: Always use the NMI latency mitigation Date: Mon, 1 Jun 2026 20:28:46 +0530 Message-ID: <29a3c970da289ab8f24282933bdb36545c0403e8.1780325517.git.sandipan.das@amd.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MWH0EPF000A6734:EE_|DM4PR12MB6472:EE_ X-MS-Office365-Filtering-Correlation-Id: 4de75048-b356-47ca-d8bc-08debfee4f9e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700016|82310400026|376014|7416014|5023799004|18002099003|56012099006|11063799006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(1800799024)(36860700016)(82310400026)(376014)(7416014)(5023799004)(18002099003)(56012099006)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: zu9+HlP/EFIY4BBe0nRexC1NETwHXnRu8Y/CtMyAPt7HxDFT1P/w+pXAb7Pttr9d0df6bPzMxpbQttfLjRFUjYZP1DpUCIW5IkQSpifeC0wIiuGNvpwI6XgmlBvWEb300B/K07hLyw6KP0w+9W12pAzM4yE1u6Udr6mTMzTdumrAbDornSJEZrA42AS3Yn2zQDETsaMWv0vZ6/O8VFQFdO8QAF9ZUqt5p+haMBF2/Y6zAElNHeDeaCSOuyYCKF63WErg1leSCXd7uI43mmkvNf/NapyzRZJMIFVsOZvMQ8opwj1RwhFPwpCXT8JJSwzDq0mva6+qUiltxjFTWhaDKQde4qlCkKao27/M1acarL3q8g+p0ILktZ72+gFW8T4jR1crv7Jfyngq+8f8unNVC3wDn7vqbnXdpJybd0a5rF2AN1tGsOr0KIX6Loacm6Lt X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Jun 2026 14:58:59.1028 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 4de75048-b356-47ca-d8bc-08debfee4f9e 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: MWH0EPF000A6734.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6472 Content-Type: text/plain; charset="utf-8" Commit df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to use a timestamp") fixed handling of late-arriving NMIs but limited the mitigation to processors having X86_FEATURE_PERFCTR_CORE. However, it is unclear if processors without this feature are also affected. When Mediated vPMU is enabled on affected hardware, it is also possible to bypass the fix inside KVM guests if X86_FEATURE_PERFCTR_CORE is removed from the guest CPUID (e.g. using "-cpu host,-perfctr-core" with QEMU). Hence, use the mitigation at all times. Fixes: df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to us= e a timestamp") Signed-off-by: Sandipan Das --- arch/x86/events/amd/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c index 6a4dfc9ecabe..6569048a8c1c 100644 --- a/arch/x86/events/amd/core.c +++ b/arch/x86/events/amd/core.c @@ -1414,12 +1414,12 @@ static int __init amd_core_pmu_init(void) u64 even_ctr_mask =3D 0ULL; int i; =20 - if (!boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) - return 0; - /* Avoid calculating the value each time in the NMI handler */ perf_nmi_window =3D msecs_to_jiffies(100); =20 + if (!boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) + return 0; + /* * If core performance counter extensions exists, we must use * MSR_F15H_PERF_CTL/MSR_F15H_PERF_CTR msrs. See also --=20 2.53.0