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Thu, 15 May 2025 13:17:48 -0700 Date: Thu, 15 May 2025 13:17:47 -0700 From: Nicolin Chen To: Jason Gunthorpe CC: , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v4 18/23] iommu/arm-smmu-v3-iommufd: Support implementation-defined hw_info Message-ID: References: <20250515171706.GN382960@nvidia.com> <20250515185629.GS382960@nvidia.com> <20250515192329.GA613512@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20250515192329.GA613512@nvidia.com> X-NV-OnPremToCloud: AnonymousSubmission X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL6PEPF0001AB72:EE_|CY1PR12MB9652:EE_ X-MS-Office365-Filtering-Correlation-Id: a52a667f-6980-45c5-423b-08dd93ed9a12 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|36860700013|1800799024|376014|7416014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?UBdzoBiMglyOU+flK/leK0Ie/Sxekz/gdJ2v0ceiE5+8fs8IMmhQfco7pySH?= =?us-ascii?Q?B8tYyPVLqR5QmH338w0FHDunT7qEt6zEVqYLmSzWsLaUJsjFakbXy5EOar79?= =?us-ascii?Q?pM6D8DOGRWevc5+sLAzRDXxM3KuIWYXPgIZpF/JsGl9jVHQj5x6bG3ruJm/Q?= =?us-ascii?Q?VMIKd7SBNo0qAWrcGg0A30MzrLSFV1NNByhQxNm9/XWb3bJ2z7/mwvvb/Lpu?= =?us-ascii?Q?SMz+k6hBrc6J2yYD/KYNPQhQENlAaojJKj7bfYIFqVZY3lDggOYdvQR72Bng?= =?us-ascii?Q?6yWWG4DQ+xoFHTDfo13pUgYLLDwftxOCJXpXanQ+42tzvdueNCVyNeHpHJXO?= =?us-ascii?Q?xt0yljjPMgaWBLociuFe+W5yeA95Yu0keZSEmd1NijpAqtDqDoQLpBguFhzJ?= =?us-ascii?Q?Kc2tantTlVg+J5o0I2k8p8nWZJzigj9oB8CbkFHEgUBoddA50HEeA5Fhvf62?= =?us-ascii?Q?fly4oBA+r6JM4axjscYb8tQ93JyayxfTj3ZsObSPqQASTnrfoE5DbutEfEme?= =?us-ascii?Q?j/4zfr7VhaaV1savasUSfbJlSB+IlzkCYZdRjfalc5hLHDEStRFjbnwkGl+V?= =?us-ascii?Q?cPl0ehGTlRNyUoRgTWrVQYb5YZlNfepkn3ZLM1FanUDYPW22z9QmwX8mOa4v?= =?us-ascii?Q?D2bkaTH7n7NWVIbG/vsJ7jI81/sqgomCx0PxEAB1xnlIWyizSBDmlWoQjwsm?= =?us-ascii?Q?Veo7ckrLbO59YJRN3zx7FMA2qM0KGVUltLpBCkVt1ScCVSEz9p1jrRBfCV9M?= =?us-ascii?Q?f9YY8EY7wlj1C65949ZOA7yT/PYR28ErAI1S/CkKch70+0Ugn801e+UEyysA?= =?us-ascii?Q?AHw7taKdfdxkefl4JspQZ5rxM9+Z0LEGBqLVhQC2gV09t8lovPIlTx9ekujC?= =?us-ascii?Q?1ICBpxPi1N5i/uwgDGdTEtLM/SBO9UUsaiD5FAQvwZQ5ktv9GDjFQrVZMW2v?= =?us-ascii?Q?/bmFsfljWLsU6lOMXgIWyxoE+QxrMGyaMGXholmYK5EtDhv7UvNZVNiuidrl?= =?us-ascii?Q?lwYqTxrdJq6+r7NW+TbHoWB837kz93BnHvSLrwYUJ5Tyw6d2qsoCKtxyCIhb?= =?us-ascii?Q?30G7WwkO3zwZXyhy39S3MufdB/ddUHhEOA7IJsX5fkqa3nH196xNuJtnCfqm?= =?us-ascii?Q?4+9kLfMG58sr72USbFdio2ZpC6VUnOHtmhBHS3E01FSnXt9SoLRk+S8QRKrV?= =?us-ascii?Q?VemzLMIK0h/EmDHXYplym4uY3gkbvdYOUoucL49zkm4/n9I2URDUOKBtzXnV?= =?us-ascii?Q?KH8kKXTvE4HX1qLSwEgzj+YwtAjf9ilkLPBR3lnQEw/iClfOaP2WVNH26r2o?= =?us-ascii?Q?yGuRLRH8gYFWaEbIgaxQYV5QMX0PGz0A4sr0O7/GdzoCisBzm3/+LPgWGph0?= =?us-ascii?Q?4Z/jrpSWOshkAqHwbzKSLjyFsjlScEIIdaSnW36MLuZh9e2GyF4efKSxN7bp?= =?us-ascii?Q?+PBLdx1xQBqSQGhnrby2Md9tq7CnfoO9eUwd06h44vkqQ4rPgQBZ5DRWcx/N?= =?us-ascii?Q?4gzezpxHyT56YD50ASQg3I33xzeYcenfDQvV?= X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(36860700013)(1800799024)(376014)(7416014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 May 2025 20:18:05.5916 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a52a667f-6980-45c5-423b-08dd93ed9a12 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: BL6PEPF0001AB72.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY1PR12MB9652 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250515_131812_660287_F212BFCF X-CRM114-Status: GOOD ( 26.55 ) 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 Thu, May 15, 2025 at 04:23:29PM -0300, Jason Gunthorpe wrote: > On Thu, May 15, 2025 at 12:21:17PM -0700, Nicolin Chen wrote: > > On Thu, May 15, 2025 at 03:56:29PM -0300, Jason Gunthorpe wrote: > > > On Thu, May 15, 2025 at 11:52:05AM -0700, Nicolin Chen wrote: > > > > On Thu, May 15, 2025 at 02:17:06PM -0300, Jason Gunthorpe wrote: > > > > > On Thu, May 08, 2025 at 08:02:39PM -0700, Nicolin Chen wrote: > > > > Should the first call return out_data_type=CMDQV while returning > > > > the arm_smmu_v3 hw_info data? Otherwise, VMM wouldn't know what > > > > to set in the input sub_data_type of the 2nd ioctl? > > > > > > No, either set a flag in the smmu_v3 hw_info, as you were doing here, > > > or just have the vmm probe it. Given the VMM is likely to be told to > > > run in vCMDQ mode on the command line try-and-fail doesn't sound so > > > bad. > > > > > > And I guess we don't need a "sub type" just a "requested type" where 0 > > > means return the best one and non-zero means return a specific one or > > > fail with EOPNOTSUPP. > > > > OK. I think this would work: > > hw_info (req_type=0) => out_data_type=SMMU_V3, flags=HAS_CMDQV > > hw_info (req_type=CMDQV) => out_data_type=CMDQV, flags=0 > > Yeah > > > Or, would it be simpler by having a sub_data_uptr: > > hw_info => out_data_type=SMMU_V3, sub_data_type=CMDQV, > > data_uptr=iommu_hw_info_arm_smmuv3, > > sub_data_uptr=iommu_hw_info_tegra241_cmdqv > > ? > > I think the former is simpler to code, you can just add the req_type > to the signatures and if the driver comes back with a type != req_type > the core code will return EOPNOTSUPP OK. Maybe just turn the out_data_type to be bidirectional? Then we would only need to update the docs: /** * enum iommu_hw_info_type - IOMMU Hardware Info Types - * @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not report hardware - * info + * @IOMMU_HW_INFO_TYPE_NONE: (for output) used by the drivers that do not report + * hardware info + * @IOMMU_HW_INFO_TYPE_DEFAULT: (for input) Used to request the default type * @IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type * @IOMMU_HW_INFO_TYPE_ARM_SMMUV3: ARM SMMUv3 iommu info type + * @IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV: Subtype of ARM SMMUv3 for Tegra241 CMDQV */ enum iommu_hw_info_type { IOMMU_HW_INFO_TYPE_NONE = 0, + IOMMU_HW_INFO_TYPE_DEFAULT = 0, IOMMU_HW_INFO_TYPE_INTEL_VTD = 1, IOMMU_HW_INFO_TYPE_ARM_SMMUV3 = 2, + IOMMU_HW_INFO_TYPE_TEGRA241_CMDQV =3, }; - * @out_data_type: Output the iommu hardware info type as defined in the enum - * iommu_hw_info_type. + * @data_type: Bidirectional property. + * Input the requested iommu hardware info type as defined in the + * enum iommu_hw_info_type. Requesting IOMMU_HW_INFO_TYPE_DEFAULT + * lets kernel pick the default type to output, otherwise kernel + * will validate the input type and may reject with -EOPNOTSUPP. + * Output the supported iommu hardware info type as defined in the + * same enum iommu_hw_info_type And similarly in the iommu API kdoc too. > Finally we end up with only one ioctl enum number space for the > types, which seems appealing. Yea. Avoiding a sub enum is nicer. Thanks Nicolin