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Wed, 23 Jul 2025 11:05:27 -0700 Date: Wed, 23 Jul 2025 11:05:26 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: , , , , , , , Subject: Re: [PATCH v3 2/2] iommu/arm-smmu-v3: Replace vsmmu_size/type with get_viommu_size Message-ID: References: <20250721200444.1740461-1-nicolinc@nvidia.com> <20250721200444.1740461-3-nicolinc@nvidia.com> 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: CO1PEPF000075F2:EE_|LV8PR12MB9263:EE_ X-MS-Office365-Filtering-Correlation-Id: aa1fb73d-a8d6-4592-bb3e-08ddca138d8a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|1800799024|36860700013|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?4Crk56w/cjTpY5MYue3xKYyPH2yHZaL6Jt/jmq5Dp4qSjL2YSwPTVnvJArv8?= =?us-ascii?Q?jh9Jk/74WSEoePNMadhWY00U6gW2eOtLAyXTWyjjjAJXE71f/yHChTONwmJK?= =?us-ascii?Q?/ShkWRYph0fgz0rPHOZ5R5mmZ5KGfiSqDhvKiqmiQUB9xQMBA9Q5/x7urges?= =?us-ascii?Q?QUxnQ9uDUHFnVnoc1jCXVntOwsOCUGS5cIN0dA0uW5EESqtfRMWSHSmbRtpF?= =?us-ascii?Q?HCsJrXweWCzxEuc5n+Hd/llTCwwz5X+efj7EGGfExRZr84aqaX3CCdWbiWX2?= =?us-ascii?Q?78+B0OmL5SQ9YUdAsC74EyCns+evyE1Z0uG+xwazoc/LYifMG7nmAuU3WUwM?= =?us-ascii?Q?ksv9MsNiTUgY6yZfdbkN0dusXjxFJkFQYi7ubtHu5PXmOjdBKTHCfGObr7b7?= =?us-ascii?Q?Bl9FlWq+DnpYRZnl1WJTrGL/Y94KfqZfTWy24OJneunbkyTLztjz7inM6sR7?= =?us-ascii?Q?yjNNErwiL9nuUZEObksOIbALBytoj9yJsDAal0ZoD+ARluauO7kLb6HGU2TH?= =?us-ascii?Q?TROADObuE9zbMOsOV7HH/IFB9FQ1f8V44TCW5rjTtVCM62DghZQHqbhe1OPN?= =?us-ascii?Q?Z4c/NTHDGOmZq8pksXZYs2F97Abb/QZseMyqHILAOrvIuYGWuxqyjKUgj6U7?= =?us-ascii?Q?wJ0rYpSfkBxr6vdI6WWnOvxDb8FP+yem5MW+SCR7w3/hj34ZqNMhCroHIf6d?= =?us-ascii?Q?qY1pXUd8xExygqBBWGBPrwninYqrUA4hI23uzlIuY1ivh/JJhQRBXw495h0U?= =?us-ascii?Q?w55Jm49smYTxgG1v0/zAxrJWoc4h37sgecOQjASAXnZItKjHRqU7XaWMa9HH?= =?us-ascii?Q?KxwEiboK4Y0wqn9wh2gvVQ8XnK4m5lEQsRm3IRi40HZTyoSTp/P8l3g78OFh?= =?us-ascii?Q?bLfMo3uMx0akKESJKukhlSInd2MOd+cypf7hfT5HgoBToXdpC+LBMiILnfbC?= =?us-ascii?Q?NJ6K4ZyD9D4imZIhITSoaD4NTiZ6zOZXWju+GyxURNMqRErh/c3GZJw9zoyd?= =?us-ascii?Q?8dpoCxUvbnI3uOszk2XeJRebsmaMpEQa6xKh/YSkdM32Nlk7YFJa1AerguIa?= =?us-ascii?Q?RrYlrtJDxEcXDFVfQCn5dDEsxn5HypkR99JLnU1bhAgpIZwxxTs9ZDrZ5Hcp?= =?us-ascii?Q?035XdjperptQIAAkyFkMB8gsWh/OpMDqx2+5waezbfVkY5GXd6COcqW5kUbJ?= =?us-ascii?Q?SAkt/JJSFNMkfB/y/U/J9K+49tF7udORLYWiVZ3g9mFduYCpfWsrtgj5IEjW?= =?us-ascii?Q?mV4sHZNYc5VxJmWdSWUko/eqHhRtmxbu6BLfQsVjpZBQWgoPD1Dn/3CCdxE4?= =?us-ascii?Q?R1V9yL+DMrgicXpGJ6mXRvBdgFV1ETwuB673lpzyYBPYK65m37diARZbv0xs?= =?us-ascii?Q?vuKkaKF370p9hnW3Zbac4yYRWVC7hE1U7Wi769xz5W4N+BA+ha/FczH3ddKo?= =?us-ascii?Q?ED8FCn/j5KRAHCXQ3fphBmVge5KJCIdvQg68FZuAvbBj3/8MqtZd9kaOS2Xl?= =?us-ascii?Q?M6ESOCxAV0s57XeJJJuFwqEPPXDVU0uKuHTll2w+oDfJeZhG65M+zeUYvQ?= =?us-ascii?Q?=3D=3D?= 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)(1800799024)(36860700013)(376014);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jul 2025 18:05:48.3272 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: aa1fb73d-a8d6-4592-bb3e-08ddca138d8a 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: CO1PEPF000075F2.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV8PR12MB9263 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250723_110556_032767_48DAFF4A X-CRM114-Status: GOOD ( 18.81 ) 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, Jul 23, 2025 at 01:37:53PM +0000, Pranjal Shrivastava wrote: > On Mon, Jul 21, 2025 at 01:04:44PM -0700, Nicolin Chen wrote: > > @@ -1273,6 +1279,10 @@ tegra241_cmdqv_init_vintf_user(struct arm_vsmmu *vsmmu, > > phys_addr_t page0_base; > > int ret; > > > > + /* Unsupported type was rejected in tegra241_cmdqv_get_vintf_size() */ > > + if (WARN_ON(vsmmu->core.type != IOMMU_VIOMMU_TYPE_TEGRA241_CMDQV)) > > + return -EOPNOTSUPP; > > + > > Nit: I don't think we'd expect a call to this if the vintf_size returned > 0? I see that in iommufd_viommu_alloc_ioctl, we already have a check: It's added in the previous patch where I explained that this is to detect data corruption. When something like that happens, it would be often illogical. > And call ops->viommu_init only when the above isn't met. Thus, > if we still end up calling ops->viommu_init, shouldn't we BUG_ON() it? > I'd rather have the core code handle such things (since the driver is > simply implementing the ops) and BUG_ON() something that's terribly > wrong.. BUG_ON is discouraged following the coding style: https://docs.kernel.org/process/coding-style.html#use-warn-rather-than-bug > I can't see any ops->viommu_init being called elsewhere atm, let me > know if there's a different path that I missed.. I see it as a precaution that should never get triggered. But in case that it happens, I don't want it to proceed further wasting precious HW resource given that this function allocates a VINTF. Nicolin