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Wed, 22 Sep 2021 01:51:03 +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 01/20] iommu/iommufd: Add /dev/iommu core Thread-Topic: [RFC 01/20] iommu/iommufd: Add /dev/iommu core Thread-Index: AQHXrSFnPBIvaGfS70e23Uj7Zne3L6uupBEAgACprmA= Date: Wed, 22 Sep 2021 01:51:03 +0000 Message-ID: References: <20210919063848.1476776-1-yi.l.liu@intel.com> <20210919063848.1476776-2-yi.l.liu@intel.com> <20210921154138.GM327412@nvidia.com> In-Reply-To: <20210921154138.GM327412@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: b5094581-5d4e-4aa1-d438-08d97d6b6fc0 X-MS-Exchange-CrossTenant-originalarrivaltime: 22 Sep 2021 01:51:03.7510 (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: EnGVvkGh3G61hGXw7/4AW+nt991q5JD7V+Lkk/hJ4xTjpqTCHLwtrBesh1GN8glSuCYKyhmyVfHg1uVONRn28A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN9PR11MB5500 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Jason Gunthorpe > Sent: Tuesday, September 21, 2021 11:42 PM >=20 > - Delete the iommufd_ctx->lock. Use RCU to protect load, erase/alloc doe= s > not need locking (order it properly too, it is in the wrong order), an= d > don't check for duplicate devices or dev_cookie duplication, that > is user error and is harmless to the kernel. >=20 I'm confused here. yes it's user error, but we check so many user errors and then return -EINVAL, -EBUSY, etc. Why is this one special?