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Wysocki" , Robin Murphy , Will Deacon , Lu Baolu , Marek Szyprowski , Chen-Yu Tsai Subject: Re: [PATCH 3/3] iommu: Do not attempt to re-lock the iommu device when probing Message-ID: References: <0-v1-8612b9ef48da+333-iommu_group_locking2_jgg@nvidia.com> <3-v1-8612b9ef48da+333-iommu_group_locking2_jgg@nvidia.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: BLAPR03CA0157.namprd03.prod.outlook.com (2603:10b6:208:32f::27) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|IA1PR12MB6433:EE_ X-MS-Office365-Filtering-Correlation-Id: 749aea48-7c5c-403c-de5c-08db98d2617e X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV2PR12MB5869.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(4636009)(396003)(346002)(366004)(136003)(39860400002)(376002)(1800799006)(451199021)(186006)(478600001)(38100700002)(54906003)(2616005)(86362001)(6512007)(6506007)(26005)(36756003)(6486002)(66476007)(66946007)(2906002)(6916009)(4326008)(7416002)(316002)(8676002)(8936002)(66556008)(5660300002)(41300700001)(83380400001)(67856001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?TP4iG4K2OZ77vNcN1HFCsmIoKEq8I5N+IEFPzIfMn5YQaeubbpw1aIlDdaYG?= =?us-ascii?Q?/iN1FErRUQk4u7dPWoNz7RbUWfFIFx/8AzIIl9L6HCRAYKl9baV2XioDNyUk?= =?us-ascii?Q?yDxkd462MVeQYWaM+4iKEo16Y3ZUX0K+VETi0mie8oC2zBneFU/4PY1sOgdo?= =?us-ascii?Q?IdhxBJvrPA4WRIhyaNytwXuQjeRHI9AOE6eVSMnl5cCmbTOhCiNEBx0mG7SO?= =?us-ascii?Q?ShcViP/T8oUmFgwNThrnCMA6RUXeLSpj9Jf9kvCAzyWQt/sb9k9SWklaoHfw?= =?us-ascii?Q?0Wo2kTBIbIXKh2qJlOTnstqiTXwmjkfMsrV5IdfqYo1yA4WR8vQ1sKyHBHyc?= =?us-ascii?Q?aqshyQd/D9GVksD12IoIZYRYG/Qyj7HC9pRIMns7Q3FO2Gt1Egl30+3/FKZn?= =?us-ascii?Q?7Y9Pc43OFH+Eumk23AlcZX+j720zadh+2iGM8De5MDMPBMHSBGqKT4SIoIun?= =?us-ascii?Q?OFpru6FA626CjCYqz4PWmnitdFi1yzsTinHYdeaIF1ZQ7ubOWLcoOC8TxJmu?= =?us-ascii?Q?L8sZHsGazXgXVZE5kgVReqmicTKkuyDQp6orVre/52EqZtF5jRe7mLDI1s7p?= =?us-ascii?Q?gRqy333bXMyk7+KcO9ur3xxSTIyV37NJccXOfTOIHU4zAhqMhdaUgbBUTeRs?= =?us-ascii?Q?jVEbIhTaVPR1KKx0p1fkepVrGgF3B2FIdn8BXC3GEbZNNDMWPwkak8m+rJlW?= =?us-ascii?Q?uAdmi3vCP6XAKX2PocbDYKl2Tz2wkuLPuN/HAC1veySOLt0MEltyABPpNHuD?= =?us-ascii?Q?WTxGypCxanB4M0p1QBmW2RRJk7Ufd/MzVsgFlVfE1JWRtJ4QD267pYkcZPj1?= =?us-ascii?Q?qpY6VdZXV7VoUbl0Lc5X+8EgTOU4MOpAzIJCE6qMyOPA8XZzortRpBm5fW3h?= =?us-ascii?Q?k7ScvQ2gPFNED4p6gAu3Rt1KK1n+QiRr1Av5cf2/wcLthLUFuh/8Uli9Jm8c?= =?us-ascii?Q?plql+FxUqOkBM6luepWRw8tRRWY8osh59FEaTgSUuWpGPV9Yw6LpNoAYYOgP?= =?us-ascii?Q?H2IcSOANd8Wibqmvug7Zr4O0VCLjFpMqjgCWw/edTXm2CLWl7hUZUw9ucVVJ?= =?us-ascii?Q?+NHKubkEQmTQbOP3YhyGpQJITEKLmwE4dE0ASKwF2HsDJx3VmIBwFtxBqYTL?= =?us-ascii?Q?yHsf5797A4zqwIuEA7tyqYFL77BOHb6RVEMk5Pms4MRsTqhdkr5LNhlbQJep?= =?us-ascii?Q?FCIXPO6QZTPAOGgZwMut0SJmL0S3d7IQXHNubvAW/iI4YD2xga99FeZS3J5h?= =?us-ascii?Q?yhUZ5nJOJxOs371S4/sDdxW3jpQ1GaCiVUe996QO0V7aETwgLEhB6K3dzgGm?= =?us-ascii?Q?yGYYo3oUi9cCMKAiLoM73yX7y0LRK9ZDa903aeIKDgQGqvRitcFTvMHs2XyP?= =?us-ascii?Q?F4R69uw3uF2zNyQxCFdVqlesQviHHH87jtyvsqyx5OdG7eLal/FNg/AOivdE?= =?us-ascii?Q?0iAGRTmBV/qZPV4MQwR1z+oZW0y5fAUsqrclWnvC9UKU//l59+uGgApZUlzZ?= =?us-ascii?Q?+Q7ILVut6OiSVaPd/azxPnt5gf/Us4oPe3p2rWULczltuPh1PF1L9XKEdmf6?= =?us-ascii?Q?4ZR4tDN/Dilr9SoVPuDFPd3Fnvlw2TJaY/YbSaDH?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 749aea48-7c5c-403c-de5c-08db98d2617e X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 09 Aug 2023 12:15:55.1055 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: W3y2BkRf0MrF84r2TzYrZhhidlL3CJ1Bni2G34y3wCw5dS1u/XI9igLZVAPxDvPt X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB6433 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Wed, Aug 09, 2023 at 04:01:42AM +0000, Tian, Kevin wrote: > > From: Jason Gunthorpe > > Sent: Wednesday, August 9, 2023 1:27 AM > > > > @@ -1800,11 +1801,18 @@ struct probe_iommu_args { > > static int probe_iommu_group(struct device *dev, void *data) > > { > > struct probe_iommu_args *args = data; > > + bool need_lock; > > int ret; > > > > - device_lock(dev); > > + /* Probing the iommu itself is always done under the device_lock */ > > + need_lock = !args->iommu || args->iommu->hwdev != dev; > > + > > is !args->iommu a valid case? Hmm, not any more, it used to happen in an earlier version > btw probably a dumb question. Why do we continue to probe the > iommu device itself instead of skipping it? The group is a concept > for devices which require DMA protection from iommu instead of > for the iommu device itself... Yeah, that is how I originally did it, but since the locking appeared here I thought it would be safer to just continue to invoke probe as we have always done. I don't know for sure that there isn't some driver that relies on this for some reason. eg it might change the group layouts or something. Thanks, Jason