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Tue, 21 Sep 2021 23:10:15 +0000 From: "Tian, Kevin" To: Jason Gunthorpe , "Liu, Yi L" CC: "alex.williamson@redhat.com" , "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() Thread-Topic: [RFC 03/20] vfio: Add vfio_[un]register_device() Thread-Index: AQHXrSFwNP3/pIcrZ0iM9X/cSoy0lKuuqYQAgAB3MFA= Date: Tue, 21 Sep 2021 23:10:15 +0000 Message-ID: References: <20210919063848.1476776-1-yi.l.liu@intel.com> <20210919063848.1476776-4-yi.l.liu@intel.com> <20210921160108.GO327412@nvidia.com> In-Reply-To: <20210921160108.GO327412@nvidia.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: nvidia.com; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BN9PR11MB5433.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: bd34bf44-2a73-4bfa-b655-08d97d54f8bc X-MS-Exchange-CrossTenant-originalarrivaltime: 21 Sep 2021 23:10:15.2098 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: LnJrThkwHq897h0JBftHYk+p41A/szMZq4pnqBdgwfJE8Sm9g0igxT6FnyYKcebK1UWbk5zlO4eBEGWPfcSpaA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN9PR11MB5356 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Jason Gunthorpe > Sent: Wednesday, September 22, 2021 12:01 AM >=20 > On Sun, Sep 19, 2021 at 02:38:31PM +0800, Liu Yi L wrote: > > With /dev/vfio/devices introduced, now a vfio device driver has three > > options to expose its device to userspace: > > > > a) only legacy group interface, for devices which haven't been moved t= o > > iommufd (e.g. platform devices, sw mdev, etc.); > > > > b) both legacy group interface and new device-centric interface, for > > devices which supports iommufd but also wants to keep backward > > compatibility (e.g. pci devices in this RFC); > > > > c) only new device-centric interface, for new devices which don't carr= y > > backward compatibility burden (e.g. hw mdev/subdev with pasid); >=20 > We shouldn't have 'b'? Where does it come from? a vfio-pci device can be opened via the existing group interface. if no b) = it=20 means legacy vfio userspace can never use vfio-pci device any more once the latter is moved to iommufd. Thanks Kevin