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dkim=none (message not signed) header.d=none;intel.com; dmarc=none action=none header.from=nvidia.com; Received: from BL0PR12MB5506.namprd12.prod.outlook.com (2603:10b6:208:1cb::22) by BL1PR12MB5256.namprd12.prod.outlook.com (2603:10b6:208:319::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4544.13; Mon, 27 Sep 2021 14:39:49 +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 15.20.4544.021; Mon, 27 Sep 2021 14:39:49 +0000 Date: Mon, 27 Sep 2021 11:39:47 -0300 From: Jason Gunthorpe To: "Tian, Kevin" Cc: "kvm@vger.kernel.org" , "jasowang@redhat.com" , "kwankhede@nvidia.com" , "hch@lst.de" , "jean-philippe@linaro.org" , "Jiang, Dave" , "Raj, Ashok" , "corbet@lwn.net" , "parav@mellanox.com" , "alex.williamson@redhat.com" , "lkml@metux.net" , "david@gibson.dropbear.id.au" , "dwmw2@infradead.org" , "Tian, Jun J" , "linux-kernel@vger.kernel.org" , "lushenming@huawei.com" , "pbonzini@redhat.com" , "robin.murphy@arm.com" Subject: Re: [RFC 06/20] iommu: Add iommu_device_init[exit]_user_dma interfaces Message-ID: <20210927143947.GA964074@nvidia.com> References: <20210919063848.1476776-1-yi.l.liu@intel.com> <20210919063848.1476776-7-yi.l.liu@intel.com> <20210921170943.GS327412@nvidia.com> <20210922123931.GI327412@nvidia.com> <20210927115342.GW964074@nvidia.com> <20210927130935.GZ964074@nvidia.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?Tb+v8KPwhRmF1sO9p7noh99xjBwY8xEvQh5GdDTMpuO8K9VbGtaj+yQW5cQ5?= =?us-ascii?Q?g7WZkqWB96quK+gqLZR2nSAeOlfRsooRuFwZIoXoZrGjbqcOYQj8MyuZpeAG?= =?us-ascii?Q?n8h+xz/DkWQf7lH7KJGDli1W9TiLQE2CfAmwnpgsjNj9/sWFsUy7epR4b8MK?= =?us-ascii?Q?Yc8uXtQxZ2UcFm4Bs5pzmJKIWlX8wIVnlMKCOiW1qn9GI7vUMF5dLkKZoald?= =?us-ascii?Q?w29hNqwF3Buk5Cjufa3CUAQ6kVpWrYGYauC2j7Twluu0KYmSuXRMGnndada8?= =?us-ascii?Q?9MqXF8mVyB8IUz2CbQo0DcPLJFTq5/xnl/FzWIEftTbxKffl1C/9cuFkCU2B?= =?us-ascii?Q?jTdwSYzEEYj1PBPdw9skr1DDf8bUY/s2WLc+yIjj3greDFA3vadrgulM+3dY?= =?us-ascii?Q?wpxbRhdvAEzF7MkEYRPxzVEydPRs/MzE4gdsG2HMh1UT8Lbdi8oq0Qu0nemd?= =?us-ascii?Q?kG5UyXuei4QtgzfNwqZFVNhzIXA6J9cGn7sW6/sy28vibucoWfF1+wzTUkLx?= =?us-ascii?Q?iMV906jt0NRQG9c9WLB/eiHE8RK0G8P7jAdK3dOnSBZNzyN24lO2EYAPKag3?= =?us-ascii?Q?YN3ktRjedr4tUyXAKCXcAajfgMpM1LBE9LgQfbUJRamfhWdH+JmpJdcYZrWu?= =?us-ascii?Q?WzSMAnegyMhaYyYBB08k8eNB9oZPW5Eh0kIxn8pPcTIh4jG79Rbn3t9Z8WQx?= =?us-ascii?Q?BOsOL/M55mi1n3bOXI6Io50UydEpAaD/BWXhAjKlUCTrUJByfpoLv2rxkQn4?= =?us-ascii?Q?RdSzCvj8lWyCWlXQ39ZHeDAN5jEqGriEa7tXweajGW0tKl7GcKLUMyDgJlNZ?= =?us-ascii?Q?inr4mHAlZRva7vXK6obqcgWz7y6/9Ol9b1SbamK7Eat1jLeE3348sH2up+BL?= =?us-ascii?Q?qhJVO8LS9YYqrNbIEs8ebSnWz7Xe/rvp2ZLpxuWalTZ4vnk0UuCuvV1aTj9O?= =?us-ascii?Q?2S5+r3L+Z/ZYufbSRWH6clhsMRShRI5GueZe4TUgo6OI1LrqfkKVooH74p9T?= =?us-ascii?Q?2uomqH93oSdxKJh1sMVBAwSfWzcfZJOHAA76rlSK4le4kEq+KLDtYfA0z7YF?= =?us-ascii?Q?I8P/H6edr8aAX4FA9BOBIff+uS6gTYOKLtp49XygGLKnpc2xMeIyFt5JAM3p?= =?us-ascii?Q?mKDlaExb/Ut9fC+UN+6IXxt63wM3bz+Caw7PyIpBtc4CbVfD/fQ572YGr/1U?= =?us-ascii?Q?UWEoPXN6+VFIppahEild3+D+UBeAcva1HE2xim9pxfawcSYVXyq3jg9WQNq4?= =?us-ascii?Q?34GUI/EfAm8rMGIP3peleEaYfvZ8tVXEyAw00KP6ZHMc2PUEkOqhqGG/l23I?= =?us-ascii?Q?ERKqQ2BLDdAPqH5nzesoOQ9+?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: a1ba7ce4-c579-4150-7177-08d981c4a881 X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Sep 2021 14:39:49.3161 (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: zd5E1+qhj4GH0tMju1wAjWClkdRuUhqPjqMgAl+xILtxoeYw1AYuFPQVL/Y6gBi8 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5256 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 27, 2021 at 01:32:34PM +0000, Tian, Kevin wrote: > but I'm little worried that even vfio-pci itself cannot be bound now, > which implies that all devices in a group which are intended to be > used by the user must be bound to vfio-pci in a breath before the > user attempts to open any of them, i.e. late-binding and device- > hotplug is disallowed after the initial open. I'm not sure how > important such an usage would be, but it does cause user-tangible > semantics change. Oh, that's bad.. I guess your approach is the only way forward, it will have to be extensively justified in the commit message for Greg et al. Jason