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mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; Received: from MW4PR11MB6909.namprd11.prod.outlook.com (2603:10b6:303:224::12) by DM4PR11MB6018.namprd11.prod.outlook.com (2603:10b6:8:5e::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9870.27; Fri, 8 May 2026 09:15:31 +0000 Received: from MW4PR11MB6909.namprd11.prod.outlook.com ([fe80::9eab:962:806:3794]) by MW4PR11MB6909.namprd11.prod.outlook.com ([fe80::9eab:962:806:3794%4]) with mapi id 15.20.9846.025; Fri, 8 May 2026 09:15:31 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Date: Fri, 8 May 2026 11:15:27 +0200 Message-ID: Subject: Re: [PATCH v10 1/2] drm/i915/selftests: Prevent userspace mapping invalidation From: Sebastian Brzezinka To: Krzysztof Karas , CC: Andi Shyti , Sebastian Brzezinka , Krzysztof Niemiec , Janusz Krzysztofik X-Mailer: aerc 0.21.0 References: <20260508080214.1979686-1-krzysztof.karas@intel.com> <20260508080214.1979686-2-krzysztof.karas@intel.com> In-Reply-To: <20260508080214.1979686-2-krzysztof.karas@intel.com> X-ClientProxiedBy: DUZPR01CA0013.eurprd01.prod.exchangelabs.com (2603:10a6:10:3c3::6) To MW4PR11MB6909.namprd11.prod.outlook.com (2603:10b6:303:224::12) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW4PR11MB6909:EE_|DM4PR11MB6018:EE_ X-MS-Office365-Filtering-Correlation-Id: 9b6dee2d-e830-4eae-5605-08deace25a3f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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This switches execution to > a kworker, which does not have its own address space in > userspace and must borrow such memory from another process, so > "current->active_mm" is unknown at the start of the test. > > It was observed that mm->mm_users would occasionally be 0 > or drop to 0 during the test due to short delay between > scheduling and executing work in forked process, which reaped > userspace mappings, further leading to failures upon reading > from userland memory. > > Prevent this by adding a PID parameter to a trusted task, so its > mm struct may be used if needed. > > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14204 > Signed-off-by: Krzysztof Karas Reviewed-by: Sebastian Brzezinka --=20 Best regards, Sebastian