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Wed, 30 Apr 2025 17:54:43 -0700 Date: Wed, 30 Apr 2025 17:54:41 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v2 21/22] iommu/tegra241-cmdqv: Add user-space use support Message-ID: References: Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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: SA2PEPF00001508:EE_|PH7PR12MB6667:EE_ X-MS-Office365-Filtering-Correlation-Id: 3b930f59-710a-474a-22b0-08dd884ac5e6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|7416014|376014|1800799024|30052699003|36860700013; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?jn6dCGp051Z8XcnHtzGRmDo376T+yPyqMZZD0PxCtRwXjmL9eR1UbYxcA2F5?= =?us-ascii?Q?iVVWpk/6GZtwWdKJX5DdPzNx7pdiL1fUKL6MJP8aOS+brnB0RGrfEgpa0mod?= =?us-ascii?Q?rpN1nAR7PtzHaNLalUGaHrnpUzThTVGCycrC7ksJvnEh7gVjF4MqQaFyjq1X?= =?us-ascii?Q?WAxfnRAfr3yGUzapXT9UJeytVyMbOTSHBCYWnqLfgozTrW244pHbp9FjisIU?= =?us-ascii?Q?uxbalxf449cvbBlhtT+uDWcYMxeiaQI+e3kAcEqHaff/SJKn5tXT85NSrCGt?= =?us-ascii?Q?u66MrC8py3DlFiTnBcHrW/szkvYQa+41hEVA7WLI9jggY9JkDuNlphin5iBx?= =?us-ascii?Q?kFBSkVuB1og6S5wlF4u12DZ88Q7JJqAJ7BQj1w9Kb23YWhsDikC/3wNnItFg?= =?us-ascii?Q?Q2otdfpmm3I/30mj6/qcDCCJv4VRjlcHiYBbx3y1+U4jKQWEvruJxnG46fVW?= =?us-ascii?Q?wJsimLrnZpQAh6kiSD2A3ahyfIU6DRijEYBeWGebexJxHcO4FL41CJiEhx7K?= =?us-ascii?Q?7QDXe9WGTvc8gYcaiFHvx1QmD2PbFHGBZbKMEF+q9igOB0qaMDSOq/LPk8qr?= =?us-ascii?Q?Mbp8nbEwAxkHyvWBsSBIHrrLS3lyCN5IPAMYocQ8DLCMNM/UP2hoz3dMw02g?= =?us-ascii?Q?Ps7R32Tlj2Fjl1BG8ikhSUyRTqoLSwrXLSjush8LC3WOn2jLTkOorhDE7TD0?= =?us-ascii?Q?Jjl0yQ7+L8tF2rukNN5n+SkYRVg3NGbyUEyNvm9Ut1UAZzIqxHi2XEIwGLq1?= =?us-ascii?Q?wtmzi1rdJIEp2V15nbl4vUML7vcb7Qmqq50x5TOrDDIVqzVzHN0s7ZFb2XjU?= =?us-ascii?Q?5uFXDRcuo7IAboTJLsOvn0TTQSCkXKpvyUeQcT0GWgEx/MpLoyemGCc7CnzG?= =?us-ascii?Q?pOtHTfQgzmlLV9HHm8yK24Yh2m1n70DWnNgFnw0GK5ywg9ykUkFQ8cehvJPR?= =?us-ascii?Q?99+oJuygiA0xeP35OfARsYJPNM5PnaH3yhlSXBh1N2bJGepuPEyLZxVSmQmX?= =?us-ascii?Q?Jl27KUcdwteaqyhunPF4KKJsmcbX8O+0lGvlOvPYpb7jsqAnb3MytBqVDWSB?= =?us-ascii?Q?RbO3SDYtxd4+QLq3QHGaEk3c6wS8AGZtckTW+2n7aS1fwVnMR2o8JiLWSGkn?= =?us-ascii?Q?rnkcEhpeubWaW/jz7Q7jwmUBijk94swtOKD39eVPatMcaRUFR7SfcI/C2blH?= =?us-ascii?Q?nIi79I22RZIUJQrNIV7luPMpxsLsFrDL5pjbi/0luMhgx0my7BWfHvjiNmlD?= =?us-ascii?Q?f1boTtCDRctZBdQKk6+P9rEXzmiLDwzr4WhYcgmB7QK4vMpMLKFNxbQy0Q0Z?= =?us-ascii?Q?6tqPaAEFzEmIjffNYt3EG7PeRgIVuExgMUJD8Y3ngKVHr1QeUgXXfC/lLv12?= =?us-ascii?Q?LxjYrdnba7SVIa4PM/MHWpz6wPCPeKyy/k1kmJDOGA6pEOaMWXWoIWDf0TlG?= =?us-ascii?Q?Ud2ih5YgSDqKUGcmlkMkkMda4/PLaNY7kn1hV1YeWMR5anaA7DszpP1delu+?= =?us-ascii?Q?xIWLlgOV8NCIjvqWcgirlMAp4qz6mEcQC3X3?= X-Forefront-Antispam-Report: CIP:216.228.118.233;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc7edge2.nvidia.com;CAT:NONE;SFS:(13230040)(82310400026)(7416014)(376014)(1800799024)(30052699003)(36860700013);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 May 2025 00:54:48.4660 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 3b930f59-710a-474a-22b0-08dd884ac5e6 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.233];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SA2PEPF00001508.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB6667 On Wed, Apr 30, 2025 at 03:39:22PM -0700, Nicolin Chen wrote: > On Wed, Apr 30, 2025 at 09:59:13PM +0000, Pranjal Shrivastava wrote: > > > enum iommu_viommu_type { > > > IOMMU_VIOMMU_TYPE_DEFAULT = 0, > > > IOMMU_VIOMMU_TYPE_ARM_SMMUV3 = 1, > > > + IOMMU_VIOMMU_TYPE_TEGRA241_CMDQV = 2, > > > +}; > > > > This is a little confusing.. I understand that we need a new viommu type > > to copy the new struct iommu_viommu_tegra241_cmdqv b/w the user & kernel > > > > But, in a previous patch (Add vsmmu_alloc impl op), we add a check to > > fallback to the standard type SMMUv3, if the impl_ops->vsmmu_alloc > > returns -EOPNOTSUPP: > > > > if (master->smmu->impl_ops && master->smmu->impl_ops->vsmmu_alloc) > > vsmmu = master->smmu->impl_ops->vsmmu_alloc( > > master->smmu, s2_parent, ictx, viommu_type, user_data); > > if (PTR_ERR(vsmmu) == -EOPNOTSUPP) { > > if (viommu_type != IOMMU_VIOMMU_TYPE_ARM_SMMUV3) > > return ERR_PTR(-EOPNOTSUPP); > > /* Fallback to standard SMMUv3 type if viommu_type matches */ > > vsmmu = iommufd_viommu_alloc(ictx, struct arm_vsmmu, core, > > &arm_vsmmu_ops); > > > > Now, if we'll ALWAYS try to allocate an impl-specified vsmmu first, even > > when the viommu_type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3, we are anyways > > going to return back from the impl_ops->vsmmu_alloc with -EOPNOTSUPP. > > That's not necessarily true. An impl_ops->vsmmu_alloc can support > IOMMU_VIOMMU_TYPE_ARM_SMMUV3 potentially, e.g. an impl could just > toggle a few special bits in a register and return a valid vsmmu > pointer. > > It doesn't work like this with VCMDQ as it supports its own type, > but for the long run I think we should pass in the standard type > to impl_ops->vsmmu_alloc too. > > > Then we'll again check if the retval was -EOPNOTSUPP and re-check the > > viommu_type requested.. which seems a little counter intuitive. > > It's just prioritizing the impl_ops->vsmmu_alloc. Similar to the > probe, if VCMDQ is missing or encountering some initialization > problem, give it a chance to fallback to the standard SMMU. I changed to this and it should be clear now: + /* Prioritize the impl that may support IOMMU_VIOMMU_TYPE_ARM_SMMUV3 */ + if (master->smmu->impl_ops && master->smmu->impl_ops->vsmmu_alloc) + vsmmu = master->smmu->impl_ops->vsmmu_alloc( + master->smmu, s2_parent, ictx, viommu_type, user_data); + if (PTR_ERR(vsmmu) == -EOPNOTSUPP) { + /* Otherwise, allocate an IOMMU_VIOMMU_TYPE_ARM_SMMUV3 here */ + if (viommu_type == IOMMU_VIOMMU_TYPE_ARM_SMMUV3) + vsmmu = iommufd_viommu_alloc(ictx, struct arm_vsmmu, + core, &arm_vsmmu_ops); Thanks Nicolin