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Wed, 2 Sep 2026 08:13:47 -0700 Received: from nvidia.com (10.127.8.9) by mail.nvidia.com (10.129.68.6) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.46 via Frontend Transport; Wed, 2 Sep 2026 08:13:46 -0700 Date: Wed, 2 Sep 2026 08:13:44 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: , Joerg Roedel , Will Deacon , Jason Gunthorpe , Kevin Tian , Samiullah Khawaja , Peter Shier Subject: Re: [PATCH] iommu: Honor iommufd uapi for zero entry_num args Message-ID: References: <20260902124333.2461949-1-praan@google.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260902124333.2461949-1-praan@google.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B36D:EE_|MN0PR12MB6150:EE_ X-MS-Office365-Filtering-Correlation-Id: 21857b00-fc30-4562-234c-08df0904dae4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|36860700016|23010399003|82310400026|10067099003|56012099006|11063799006|13003099007|18002099003|22082099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: yzTDU9TdCWawJ43DAE6FXbaa2/q+1auU9iqSJ+jExfzxU719JW4NFwpFB7u8QavR6NkqAOJ1DVrRaulKAG+pqr6+yteNuPW/br02rloTO5zDGhRtIzmcssJqUqz3hVGxxoLcQwLW1bcZCSzkppPWxVE8e/rT941IZYcSLycGdQPnP14giP31w/MwJMTMk3DTJB6XSo/gYQLr3pd06rhvaGlH7eun5uq7behX3SYKnaeUbyO/l5Sqtl0uke/WxZKf5vVTDMCewjTbI9a89sJKFi+UAuNCW/94vm/N8goKRyRZ6X/IoEYZGlHfmKGjM33XxEG/yKv9Uu2X/Lrip8bSl0PIvLw3y8CN1xhe0kUgAvBeEIznBRhCKqSgZohW0yamFdb+j2TKD+OviypJ+eAYImv00BMn0MPYaIw7UaFw5kQWBCMIOkToBx99kDZtST/e X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Sep 2026 15:14:16.5022 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 21857b00-fc30-4562-234c-08df0904dae4 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B36D.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB6150 On Wed, Sep 02, 2026 at 12:43:33PM +0000, Pranjal Shrivastava wrote: > The IOMMU_HWPT_INVALIDATE ioctl uAPI explicitly allows an empty > invalidation request array by setting entry_num == 0. The uAPI > documentation in include/uapi/linux/iommufd.h mentions: > > " An empty invalidation request array by setting @entry_num==0 > is allowed, and @entry_len and @data_uptr would be ignored in > this case." > > While the core iommufd_hwpt_invalidate() handler honors this by > skipping its bounds checks, the generic array copy helper > iommu_copy_struct_from_full_user_array() incorrectly rejects it > by returning -EINVAL, breaking the uAPI. > > Fix this by returning 0 instead of -EINVAL when entry_num is 0. I think the caller of this API should be aware of that and check the entry_num. I have submitted an SMMU patch doing so: https://lore.kernel.org/linux-iommu/5223275dbc8ef00af233f3fee01efa09e45f26b5.1788127877.git.nicolinc@nvidia.com/ Not very sure this API should be changed though.. Nicolin