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Tue, 8 Jun 2021 13:15:49 +0000 Received: from BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::3d51:a3b9:8611:684e]) by BL0PR12MB5506.namprd12.prod.outlook.com ([fe80::3d51:a3b9:8611:684e%7]) with mapi id 15.20.4219.021; Tue, 8 Jun 2021 13:15:49 +0000 Date: Tue, 8 Jun 2021 10:15:47 -0300 From: Jason Gunthorpe To: Paolo Bonzini Cc: Alex Williamson , "Tian, Kevin" , Jean-Philippe Brucker , "Jiang, Dave" , "Raj, Ashok" , "kvm@vger.kernel.org" , Jonathan Corbet , Robin Murphy , LKML , "iommu@lists.linux-foundation.org" , David Gibson , Kirti Wankhede , David Woodhouse , Jason Wang Subject: Re: [RFC] /dev/ioasid uAPI proposal Message-ID: <20210608131547.GE1002214@nvidia.com> References: <20210604092620.16aaf5db.alex.williamson@redhat.com> <815fd392-0870-f410-cbac-859070df1b83@redhat.com> <20210604155016.GR1002214@nvidia.com> <30e5c597-b31c-56de-c75e-950c91947d8f@redhat.com> <20210604160336.GA414156@nvidia.com> <2c62b5c7-582a-c710-0436-4ac5e8fd8b39@redhat.com> <20210604172207.GT1002214@nvidia.com> <2d1ad075-bec6-bfb9-ce71-ed873795e973@redhat.com> <20210607175926.GJ1002214@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?GKnTkeXvj5zfgWuxJbOezaILbBkr47V0fpTC6Gwi47ivYQS1CTr/WqOPYwTA?= =?us-ascii?Q?V5Q43tTYOci9xDNGigd5XqW51LsFcZGJFl8Z/BScF2OsDI1BBKipgDifeYgV?= =?us-ascii?Q?9iGXZmPdAg4YG3lOreZc2cU4k2cscZWg106NhZ7m/jRpmGiLsSoJwEk2+LQz?= =?us-ascii?Q?3F0oGTq1U1wXdvL2LqhFfce0dHvetdP3C5VkVVTiXlo7BiHTcZ6gW1eXPtxu?= =?us-ascii?Q?HRCXSEy77VJpZdFxUMq4jHdaa/fcK82saOVfuSlK+L0OOHPGEhLB+WwZnY3m?= =?us-ascii?Q?Bme3dfjHJBD5mPhJTWyySqi4B6ZmihV7zhoD6QGVLje8d2X8qqp/pvst2NiX?= =?us-ascii?Q?hk7HPo2UsH511nRO26Qd3/kYiBUgJObMy/GjDU2+AHqafdOb75dqnjlIWFxf?= =?us-ascii?Q?p9L6Hd98Uj54qQJVuanD19n11e4wg6IIl0q5NQUux15DMfBOQ1Fu+GLrFqkw?= =?us-ascii?Q?nr8oXpSoB3iWNIzjK7DWgE6MbzezMLVMBhLSYrwxqQqh10OCCkl9Ibl9M7Uq?= =?us-ascii?Q?uC8ZjA9oozcGBJINw1KrzPS97mRyhtFZT08O7NgpnoH2qIlR769YCq0oAVfX?= =?us-ascii?Q?hJnPt2evkD75yD/26CAGWBtTeb/Gw1COCp1JRnmPAAOkhuCTF5q0plUmJuEQ?= =?us-ascii?Q?K9dMkazFbpIiro1oeJfaxeV0ilHK3NDRjI0q+TpU4xD4p0eXAqEtnuGOgcXI?= =?us-ascii?Q?ymNMz3fV+rtHWY+8M1iwkgdb9Pan6pbECWJU2nd7oY9JMcxcp2q9/5CaWvc+?= =?us-ascii?Q?g2H7qWucyHZ97GjkK+Ve7IO7gmfem3wCA4YFocnWqOUEXpUNU2Q7YhQhMHyG?= =?us-ascii?Q?SbACuvA/tSFCkg1lOeHD6nwEuUsKsghRLgTgd50ym3daIZGU1WQzM/3PFNmr?= =?us-ascii?Q?6qpwOrLbc8AOVGbIeR83yHcg9BWCCPAJMN8M2HDJJ7RvnjDKo50cLuEQNH77?= =?us-ascii?Q?znGEIZpbBdHJha/A/mqL/d5Ejtzng+Tg+NCEwknRNG29un0Rd23HMbZjLG6O?= =?us-ascii?Q?YUayAXqvMgm3Q/lHcTo0Y8UqYNB9fXQYaK9/Qvf4u8sbyStlqHoBRLZf2i/e?= =?us-ascii?Q?XYaO+nPCEJeTt4xf+/0jjb7u5kWuHTfkqBMPwbv+QfWqOUzPxiPupcX3eran?= =?us-ascii?Q?FKwVLHasdlJ4j1b6bc7R5iJ8ZKlVN71e2ED07flGWvtXI9eYTHbhLZGc02ia?= =?us-ascii?Q?iGn+vMOJPtTXrrb9W2v4wskojnIGLJJTHZCQXpPDMxLj0xU1fIbTAObjJIlR?= =?us-ascii?Q?LbSfG0sviG59OGPti8yboAQEccG5DLG1+irM/qb32mrsf8UN3vrdbUlb/fp9?= =?us-ascii?Q?OXGbG+7Ngzo2nWc61Ur/4zwF?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 25b23e3b-f899-4715-5430-08d92a7f88d6 X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jun 2021 13:15:49.5622 (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: +JQz/FBDW4Fb9FwHCZ56NkijwBD+vGH67A7sEHhhL1IvQndU6XD4vvpnhLGdNKUJ X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5206 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 08, 2021 at 09:56:09AM +0200, Paolo Bonzini wrote: > > > Alternatively you can add a KVM_DEV_IOASID_{ADD,DEL} pair of ioctls. But it > > > seems useless complication compared to just using what we have now, at least > > > while VMs only use IOASIDs via VFIO. > > > > The simplest is KVM_ENABLE_WBINVD() and be done > > with it. > > The simplest one is KVM_DEV_VFIO_GROUP_ADD/DEL, that already exists and also > covers hot-unplug. The second simplest one is KVM_DEV_IOASID_ADD/DEL. This isn't the same thing, this is back to trying to have the kernel set policy for userspace. qmeu need to be in direct control of this specific KVM emulation feature if it is going to support the full range of options. IMHO obfuscating it with some ADD/DEL doesn't achieve that. Especially since even today GROUP_ADD/DEL is not just about controlling wbinvd but also about linking mdevs to the kvm struct - it is both not optional to call from qemu and triggers behavior that is against the userspace policy. This is why I prefer a direct and obvious KVM_ENABLE_WBINVD approach Jason