From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4A727C7EE2A for ; Wed, 25 Jun 2025 20:58:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:CC:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Ay+OoYaAjDj9hZe+qVQx/WgvfjaQQCv+QQtBOyngybE=; b=TGXLCPTmdXtqCEPo5Gc4INOK2/ LILBOw8d3L53xO2Wa9UXRQxAiwYo2hy7yah0KDeOSe8NRaztoNYzdFtiYiszTNSWltE+g128qdsi0 BP++d1KUMvFvwzUSGhAE0pg+ZFkRQrYUDW4Ea/cBuU6Rpxh7M4LwWsF1Ydm8XAaBF93tVOHvcA3X2 idZVQ6uGLy/BgxkfCR1dpsFj3balv8l671wL/ND6vEJrAzH2jmae2H9dh6TQHnIJwgPaHHHDvmzzL NWZArenk03r5K5wduU12Fl00MxrDEopVCiK+ILr2MTp95LbY2v2rV6GpLH8/unbN4zN3Anut8ip24 XK2EKZtw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUXCG-00000009vUT-0VuS; Wed, 25 Jun 2025 20:58:20 +0000 Received: from mail-dm6nam10on20621.outbound.protection.outlook.com ([2a01:111:f403:2413::621] helo=NAM10-DM6-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uUU09-00000009Spj-0nLZ for linux-arm-kernel@lists.infradead.org; Wed, 25 Jun 2025 17:33:38 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=iMDQ4KE48BVzvysYtGAeiFuyzPFsp9zbyT7/j5LFxGC9knjA6Xei8TBIAlQ47o2FfPsTqw0uhHQ2gb8M3fcXlz3/HOHo5sNBWizEIonYKor1VIQ2VhUlqKVmLtP+E+akO5xK1tzrfDgUxMBuLCzBTiX+SNLwJHnu0/cWcksyTjMGa8v9fpqxCb5V+p6b/330y3sVkE7sH0t1uH0JkVY2b2nLj0yFuUI7yfKPBB0hsPQlF3vFO+jPPVNeEvp4ANL0o2XvUj3mN1E+kPPSobLI4Kv9TGD1MtILEcBHA1Uc3wPsZq13jcTXtCm4T8WitUC4zYxv2nBEQ3XksXxUW9H0Ug== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=Ay+OoYaAjDj9hZe+qVQx/WgvfjaQQCv+QQtBOyngybE=; b=eTZVt9FRojx02Xtmwyv8CahpQ8guIcYQ7vHeHt0aUoBOtm5z4RmrwQ+RJ2Sts47BYofNL1qBhdN9j2zAAiRl/gP9LQiSvMyk1mRdPCLQROexAoMruGfgGjCu8WvoVHOppsPjo+wUK97EhtlEDtIF+6Xto8ttUPk2jo8saqydAToO6ExhLaYBG+k8PhUF0jCdqUXLGtEFGSbvfFE1l4OTV7AgCQhPxWTn3pYE8gGx0jz34qtHMusKk1tXSEOPjAPvFxk6pnC5Vc9y+b/VLMGfH3Jgi7UaGb1mpM4g0UyJIla66iEsocDjRhoZoxE/LCYJvHA6v5m9T22sJNnLAC7lEg== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 216.228.118.232) smtp.rcpttodomain=intel.com smtp.mailfrom=nvidia.com; dmarc=pass (p=reject sp=reject pct=100) action=none header.from=nvidia.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Ay+OoYaAjDj9hZe+qVQx/WgvfjaQQCv+QQtBOyngybE=; b=rTxzWXXjRjN7JGPzwJGr8aiJ4kjIgVZMSWEUNAh4z3sOBIUp+lmuftlnp6DlLKCc5Gs6DDU04ypPgiLF++vtB6S5fsnpQ+qQXYWSFzEosZSZuJcQPcHwF5HijTJxgvB9iEDKfemYWyA2+/Cfncfvh9NaMbmpXbi8gk0U9n5YRM/yTOFEWJrPXtDN6cOAQr8T5RsBsqZ5xCNXyY51a+lj7QfA+JpZ9QRplMTH9SjcalmI0yroCyG9slqsgHVqD7h7TSIafyubeyBbk72l5AvG5+tJraNBdbLH07q542QpZmmnZbfrXIli1lsDzcI4NhU5bOLgjc57xjTZ1f1bYoXxAQ== Received: from BN1PR13CA0028.namprd13.prod.outlook.com (2603:10b6:408:e2::33) by SJ1PR12MB6243.namprd12.prod.outlook.com (2603:10b6:a03:456::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8835.30; Wed, 25 Jun 2025 17:33:22 +0000 Received: from BL02EPF0001A101.namprd05.prod.outlook.com (2603:10b6:408:e2:cafe::9d) by BN1PR13CA0028.outlook.office365.com (2603:10b6:408:e2::33) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.8880.16 via Frontend Transport; Wed, 25 Jun 2025 17:33:20 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 216.228.118.232) smtp.mailfrom=nvidia.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=nvidia.com; Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates 216.228.118.232 as permitted sender) receiver=protection.outlook.com; client-ip=216.228.118.232; helo=mail.nvidia.com; pr=C Received: from mail.nvidia.com (216.228.118.232) by BL02EPF0001A101.mail.protection.outlook.com (10.167.241.132) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8880.14 via Frontend Transport; Wed, 25 Jun 2025 17:33:20 +0000 Received: from drhqmail202.nvidia.com (10.126.190.181) by mail.nvidia.com (10.127.129.5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.4; Wed, 25 Jun 2025 10:33:12 -0700 Received: from drhqmail201.nvidia.com (10.126.190.180) by drhqmail202.nvidia.com (10.126.190.181) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14; Wed, 25 Jun 2025 10:33:11 -0700 Received: from Asurada-Nvidia (10.127.8.13) by mail.nvidia.com (10.126.190.180) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.14 via Frontend Transport; Wed, 25 Jun 2025 10:33:10 -0700 Date: Wed, 25 Jun 2025 10:33:09 -0700 From: Nicolin Chen To: "Tian, Kevin" CC: "jgg@nvidia.com" , "corbet@lwn.net" , "will@kernel.org" , "bagasdotme@gmail.com" , "robin.murphy@arm.com" , "joro@8bytes.org" , "thierry.reding@gmail.com" , "vdumpa@nvidia.com" , "jonathanh@nvidia.com" , "shuah@kernel.org" , "jsnitsel@redhat.com" , "nathan@kernel.org" , "peterz@infradead.org" , "Liu, Yi L" , "mshavit@google.com" , "praan@google.com" , "zhangzekun11@huawei.com" , "iommu@lists.linux.dev" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-tegra@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "patches@lists.linux.dev" , "mochs@nvidia.com" , "alok.a.tiwari@oracle.com" , "vasant.hegde@amd.com" , "dwmw2@infradead.org" , "baolu.lu@linux.intel.com" Subject: Re: [PATCH v6 06/25] iommufd/access: Allow access->ops to be NULL for internal use Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL02EPF0001A101:EE_|SJ1PR12MB6243:EE_ X-MS-Office365-Filtering-Correlation-Id: fc3bf00f-a8b4-4a94-0640-08ddb40e60de X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|36860700013|82310400026|1800799024; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?Xvg1vGQEWv8PvdcMD90bZq63guzx/PT0227WMo3s95vpbBnYMD7wWDttUk3s?= =?us-ascii?Q?hR8OkpB4LqXQMNOWInvqk2Yiun2rcOvaiwNPjccu+4souQFxWF7OBKLm9LXS?= =?us-ascii?Q?TydMm4fsxX2+WZKQ8pWkgqnBrv2qa2xWUQmBEYPS9Yw+gEtmhkiP/Laho6Ab?= =?us-ascii?Q?QqpNBcrG2OQbSKe1a8lPu5ojWckUWiqGy3Yt3kpXlPQLyES9JTPBbPMhjq22?= =?us-ascii?Q?vr0nPnbiySSVwckzBfg67QIabIjrJnD6/m0aBFkOlH8ZJzNd1ioEp1f9N1Cy?= =?us-ascii?Q?KF9z4Ir1wTu6gqLosOcfn2QaC0Ejx24U5nMNkpNToO4pIDi4hFgBxUgHyW4Q?= =?us-ascii?Q?aGH5sMZlqT2gDE0eNR6XD2P57uWZQEX3/8RnOcwndhD/b8XVKfIydPAFpKOH?= =?us-ascii?Q?WEoq47RN6kKMOb+Fqeej3Hcjs+9G40hfo8gBaoFGlkGNj+8vRSolV6YyfObm?= =?us-ascii?Q?Zy59muMV0o+Xzz4DU5CawYWXfthMQinUEF/IFA40e+R4cuCx6DO/s9+2NpKU?= =?us-ascii?Q?5IERosOTsoqMECDG/LGfYmXOeuKLeq9rjb6wgqjdQEObHCJ/9TcZGz3j1oFU?= =?us-ascii?Q?obWTD66Ehee32h8N8IcJd5fjWFhNtH528vSs+t6RCvIIkHIaxjJYk6pEHXmA?= =?us-ascii?Q?aCD/5AzYYRwCUsHRFioTQy8tE6dsOzQ4bkDA7WOdUg2BBKw4n5MNIJchAHmU?= =?us-ascii?Q?IZQEIfuTFY2ODXSxfEQkr/Lr4nCaJ+t8R5ZBMspb+JlvQgWC/YoXAfvo5tp/?= =?us-ascii?Q?ZCHNAOR6u/bqdBkSpTBx3J4Dmc68dccxatRWZmv1UWNCn2iEQ8kKzXfVY3EV?= =?us-ascii?Q?PemV+MXX6iJgPNVWmpxqWKs9QRMnqqcPlT6kJMg2dFjR4INhz3KasuTFn0Kq?= =?us-ascii?Q?O5YztEuICZi0irg/VPxCxiUkXFojCZ9H/h+UKG2ssA1ERQencrV140AfMkd8?= =?us-ascii?Q?RWCOfXqJaMd72GVIVXWYiyDq2OT06kC/+I2PwG/a6mmZuo4/etLN4g2qPSJO?= =?us-ascii?Q?G+bXQrK5uXnPzCXY84wwciWzXyDcRWttERukutzfSkVzmbD4+R95THBX2Wdg?= =?us-ascii?Q?IeIR1Ez2e+GRKIEsJiVCtf09WFkUTVFVEhiHDzPLUjHWoxvuu390jHkKchy4?= =?us-ascii?Q?vYFPRuYn3zGC6X5Ye/5p3qmGOBp1KFiFhe42w57/6niu/ScHt4u7mVXRdo1u?= =?us-ascii?Q?g0gJ+JjlJ+68sF9pVEVYuEvo2fbUhySjZaxnsLSfz3J7NN3ZFaLJPsYNuKuI?= =?us-ascii?Q?R2k97t1BnXwFygweJJWicBxNrFTBuF4T4+zqc2YqTZ6L9N1IzHzxSVEfJhVb?= =?us-ascii?Q?IRbDgDduU1934Sa7dfwFaaxiSlCcpnbP2RV/IUSphWRUQ8SfZKb2/oCp2PTV?= =?us-ascii?Q?fKTT5rlpGioJakzgpQdSdbzUC3xWphZOrvdOSGJ6GidJl1Pe2ChPjzKAVzd/?= =?us-ascii?Q?gvnI6DMa+puyK4b/6hj7xvyjMVIZPF9xCqhbcn6aM/9nJ0aUHJehjBvhQAYs?= =?us-ascii?Q?QjOCg0MlNZ4qA0zWLoOsDM65oXCeJB48jDsj?= X-Forefront-Antispam-Report: CIP:216.228.118.232;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge1.nvidia.com;CAT:NONE;SFS:(13230040)(376014)(7416014)(36860700013)(82310400026)(1800799024);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Jun 2025 17:33:20.2388 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: fc3bf00f-a8b4-4a94-0640-08ddb40e60de X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BL02EPF0001A101.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ1PR12MB6243 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250625_103337_224415_F1295B24 X-CRM114-Status: GOOD ( 21.87 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 25, 2025 at 09:37:18AM -0700, Nicolin Chen wrote: > On Wed, Jun 25, 2025 at 03:38:19AM +0000, Tian, Kevin wrote: > > > From: Nicolin Chen > > > Sent: Saturday, June 14, 2025 3:15 PM > > > > > > +int iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long > > > iova, > > > + unsigned long length) > > > { > > > struct iommufd_ioas *ioas = > > > container_of(iopt, struct iommufd_ioas, iopt); > > > struct iommufd_access *access; > > > unsigned long index; > > > + int ret = 0; > > > > > > xa_lock(&ioas->iopt.access_list); > > > xa_for_each(&ioas->iopt.access_list, index, access) { > > > + if (!access->ops || !access->ops->unmap) { > > > + ret = -EBUSY; > > > + goto unlock; > > > + } > > > > then accesses before this one have been notified to unpin the area > > while accesses afterwards are left unnotified. > > > > in the end the unmap fails but with some side-effect incurred. > > > > I'm not sure whether this intermediate state may lead to any undesired > > effect later. Just raise it in case you or Jason already thought about it. > > That's a good point. When an access blocks the unmap, there is no > unmap happening so no point in notifying devices for ops->unmap. > > And, when the function is re-entered, there could be a duplicated > ops->unmap call for those devices that are already notified once? > > So, if we play safe, there can be a standalone xa_for_each to dig > for !access->ops->unmap. And it could be a bit cleaner to add an > iommufd_access_has_internal_use() to be called under those rwsems. Correct: it has to be under the xa_lock. So, this pre-check needs to be done in this function. Thanks Nicolin