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Wed, 22 Sep 2021 23:56:41 +0000 Received: from BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::e8af:232:915e:2f95]) by BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::e8af:232:915e:2f95%8]) with mapi id 15.20.4544.013; Wed, 22 Sep 2021 23:56:41 +0000 Date: Wed, 22 Sep 2021 20:56:39 -0300 From: Jason Gunthorpe To: Alex Williamson Cc: "Tian, Kevin" , "Liu, Yi L" , "hch@lst.de" , "jasowang@redhat.com" , "joro@8bytes.org" , "jean-philippe@linaro.org" , "parav@mellanox.com" , "lkml@metux.net" , "pbonzini@redhat.com" , "lushenming@huawei.com" , "eric.auger@redhat.com" , "corbet@lwn.net" , "Raj, Ashok" , "yi.l.liu@linux.intel.com" , "Tian, Jun J" , "Wu, Hao" , "Jiang, Dave" , "jacob.jun.pan@linux.intel.com" , "kwankhede@nvidia.com" , "robin.murphy@arm.com" , "kvm@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "dwmw2@infradead.org" , "linux-kernel@vger.kernel.org" , "baolu.lu@linux.intel.com" , "david@gibson.dropbear.id.au" , "nicolinc@nvidia.com" Subject: Re: [RFC 03/20] vfio: Add vfio_[un]register_device() Message-ID: <20210922235639.GD964074@nvidia.com> References: <20210919063848.1476776-1-yi.l.liu@intel.com> <20210919063848.1476776-4-yi.l.liu@intel.com> <20210921160108.GO327412@nvidia.com> <20210922005337.GC327412@nvidia.com> <20210922122252.GG327412@nvidia.com> <20210922141036.5cd46b2b.alex.williamson@redhat.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?sDHllDH0m7zHp/Du6dxGTs3u1tPA36EWrwdIYaipRkdI9JRAm27lTq8eUufR?= =?us-ascii?Q?pz08wxGjQXuEbtIJkrlL1yxlvMbjbEwu0K7rzurBjxOA9B0f2c+22gOh6+9d?= =?us-ascii?Q?WOG6ugpjyQbud3pmqZDhKYQRpmXxvFrcEuRKkH2dXl8iDjAmcGrsyvkCQUXE?= =?us-ascii?Q?ApjrDVqLkaqW4QJGvM9dBGf86wfwjVozidCMnjY+rGBfDbeEZ/THFLwHlkRV?= =?us-ascii?Q?WEJPmk1b73Lqv613/HZIrC/SfaVf+NRRvooh+2VCKSlnmSz9POxWLwKlplK4?= =?us-ascii?Q?6/QYymnCgELZun6xfqCg6hQ8HxIY77aZ7e/+kDgxGz9b1jfWowNDEpc3M8Dz?= =?us-ascii?Q?xSsUIcJlylrfIwl35C8ExJdhrGRX3w3J4iak/OoJpmflrqAN40LG4EGYinDJ?= =?us-ascii?Q?BO2sWEi5XEEmmPFnZjxTrgTTb/01m98xe1vcwVucnmZPmiuxEtjr4QcLpdBW?= =?us-ascii?Q?vMSfHv/pIPKWNcX62l6wpN4qZdjJOTrVUhLndO49VPDF1M6KJTprTC814wvY?= =?us-ascii?Q?ZEFKTKF0n5zh3MCksNYfSqaTzd4eMF8u622GmbXttxZpCiL48RfBBsLDxHWH?= =?us-ascii?Q?i3VOpDOjlIGOGtdzGy46cL6/6RVPXgL6nNtUrw/tA9IXhvEvfQjsi+0Airf2?= =?us-ascii?Q?l7B+u0tNElOmv3KJahuZF+YoSYQXa5mjIFmemOV0oAR8gcD7GD789lHxt2tq?= =?us-ascii?Q?V50Yw11yrlKWZFz7jKnRvRf7wCt3nhkOSPmWk1xVZdZor3BVAYpYY2YnXVhC?= =?us-ascii?Q?ZgaT3CZ2vckNbNY1j+mOD9dIfuSPMBBUqF2eubAmn7lZIXeZL+oI4veG6wuC?= =?us-ascii?Q?TVHy+m6R9oGYwsTHd/8KZNxZDCzhd3oFc9Ye4Qqp8oIxuOAP9nY3+PklbuQh?= =?us-ascii?Q?BRO6gYzW2JMmIrMIE+Ad4QiljFP39HHqx+6VoL8+hXoS3fjodoFs1G+EWiDg?= =?us-ascii?Q?O9o3F30CDaEbIeHXiefgjLEGUDAmYP7O1CFsPAas299K1zs/4JQ6TyiaS4d4?= =?us-ascii?Q?PwS4DgeieceU69+TPFXP1Xqg4xb2h8EZcIg/9aCHY7skq7oI7mWd49ZyQHXh?= =?us-ascii?Q?5k/JzXjSQVk819stneO3qAyIZZLRYaw0Mpw9H69e7SCDim0rtGPqPOHhbxu6?= =?us-ascii?Q?1KFtGqC+A3eNY2jNOcivADwbIrdaiCRlhWhe604dr1qSJr73iuEJmzANp3Ou?= =?us-ascii?Q?iITlP1TKdxDP7obm9am4I8uwZpyUvqUAQFEgEKqofx+QIhki0YPYS1dIhqlY?= =?us-ascii?Q?sWawujo1wfh4z+6vvP1ioD/iNFAF5KhRNtd4sZKhprOAtw7EfAkKjoU4khRS?= =?us-ascii?Q?iUO3DfxN5iaEbcYW7+Z8JZqM?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 3c637aac-70e6-4222-04b3-08d97e249f73 X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Sep 2021 23:56:41.1232 (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: XKTMOFvQhc9PbnzV4ELroYIBAsvOndNfxxnooMbdpnYOUEYMMzHo/Hmd6uZmz9lV X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5111 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 22, 2021 at 02:10:36PM -0600, Alex Williamson wrote: > But why would we create vfio device interface files at all if they > can't work? I'm not really on board with creating a try-and-fail > interface for a mechanism that cannot work for a given device. The > existence of the device interface should indicate that it's supported. I'm a little worried about adding a struct device to vfio_device and then making it optional.. That is a really weird situation. I suppose you could create the sysfs presence in the struct device but not create a cdev. However, if we ever want to use the device fd for something else, like querying the device driver capabilities or mode, (ie clean the driver_api thing wrongly placed in mdev sysfs for instance), we are blocked as the uAPI will be cdev == must support iommufd.. 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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, Sep 22, 2021 at 02:10:36PM -0600, Alex Williamson wrote: > But why would we create vfio device interface files at all if they > can't work? I'm not really on board with creating a try-and-fail > interface for a mechanism that cannot work for a given device. The > existence of the device interface should indicate that it's supported. I'm a little worried about adding a struct device to vfio_device and then making it optional.. That is a really weird situation. I suppose you could create the sysfs presence in the struct device but not create a cdev. However, if we ever want to use the device fd for something else, like querying the device driver capabilities or mode, (ie clean the driver_api thing wrongly placed in mdev sysfs for instance), we are blocked as the uAPI will be cdev == must support iommufd.. Jason _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu