Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 29 Oct 2021 09:44:52 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     David Gibson <david@gibson.dropbear.id.au>
Cc:     Liu Yi L <yi.l.liu@intel.com>, alex.williamson@redhat.com,
        hch@lst.de, jasowang@redhat.com, joro@8bytes.org,
        jean-philippe@linaro.org, kevin.tian@intel.com, parav@mellanox.com,
        lkml@metux.net, pbonzini@redhat.com, lushenming@huawei.com,
        eric.auger@redhat.com, corbet@lwn.net, ashok.raj@intel.com,
        yi.l.liu@linux.intel.com, jun.j.tian@intel.com, hao.wu@intel.com,
        dave.jiang@intel.com, 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,
        nicolinc@nvidia.com
Subject: Re: [RFC 20/20] Doc: Add documentation for /dev/iommu
Message-ID: <20211029124452.GW2744544@nvidia.com>
References: <20210919063848.1476776-1-yi.l.liu@intel.com>
 <20210919063848.1476776-21-yi.l.liu@intel.com>
 <YXs9IwqYHvUUXePO@yekko>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YXs9IwqYHvUUXePO@yekko>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?cx9bd1RUVR6B6gzOX3YC0H6trKkQeIhIOPZMGy22qOT2Z7LOmCTi4P75Hqg5?=
 =?us-ascii?Q?GN9ftXMoBd6w06PQkD4TvBqpT0uYe7EOnpoqfEbcydMGY8JC2jQ9SxBO/CpZ?=
 =?us-ascii?Q?AbdYBGgJXtKbeDucV1SqJESeN82wfMIUe+xp0nrQ2fzCx/r89pGUCFSsKAdd?=
 =?us-ascii?Q?uFei0GgfLlMik9RnzanVUs/qmoK0PXOxA1lSEectiJx3+7EiOJFhrY9EI5QJ?=
 =?us-ascii?Q?Ao6tavHOopYbf78ew3EN77wLLe+TWZgrESDJoWizJ88e2WrZFabZvaIZx3SO?=
 =?us-ascii?Q?JDRsdCZhsId9EenhQbsEEouzA7+nH8NyGl0RN8vlxY/hR6q6Sc1VMurS3J+A?=
 =?us-ascii?Q?UZNmBlVU7uXYe65agJgGxFzd5KUtdHq3UJzK+AE5IiDTMBjiynegarzSrAo1?=
 =?us-ascii?Q?/kRp+jWCq7BtVeWvCV0OIokfGfCBl1yvklm0aWLvACxOqnbVsQjwWrlM50y6?=
 =?us-ascii?Q?gR9Yzvr19b6YknQ8DVztsUAyvFm4USqSMAfB1eqc9ldbPJoU8s7EIA0mjR4+?=
 =?us-ascii?Q?OE63jwQFBxQnmTfuAYNqhJve5YC9m1hhuXfreW+0sVZFLrXdunLsbF4cZF4x?=
 =?us-ascii?Q?HUO9yAvMXywztKXvEMBbeJA9+z8RHzVyVf+CNE/RKyRuDnCOXDWalnVhoW0G?=
 =?us-ascii?Q?Yz6b0SAkTF3LGQ5/HJQj3ZIwpDkLmiFowzAbqkU9xYTleojhurHdj0QqV/5I?=
 =?us-ascii?Q?OR1u10jeQWi8ziHGBfYz85T7Q14/7XY4opxaNbEoU0saumruluGd4TxsqriM?=
 =?us-ascii?Q?xVS3k9Bxm9GnnxhIeGXIb2ThR2L3rhoRHAySRTGlYN5Wm0sIlJxhQPirWkJb?=
 =?us-ascii?Q?Y2r/RdOwpUiXsFtjuX7JH+oZcN4G1wBdoEQ4skHBezZz46RB82BUtL7CHnGX?=
 =?us-ascii?Q?ygD2Bx661QS7lfvYZIC80Jjhe+u5B7QTacfqEWFieF4AkMxkNhHBGVw68WOL?=
 =?us-ascii?Q?rEnX9Htc9Lx89hxiEhhsc5wt6w92hMM0Xnj146+GuCwobG43CWP0MAG7cbNb?=
 =?us-ascii?Q?l/XTO74nhQrMEvyTa3/s3DUqIwBCetHRuVRbpXiT1oj6g62CJt+8j/6y3d1Z?=
 =?us-ascii?Q?Kx4AITNl4wITVAkdXnVv8Fx5FFl1QU3vMGf0kkujoWKTkOzok8ZRlm3IVz3z?=
 =?us-ascii?Q?aPjVBe91n2hwall1Krn23eJUtR9HWIjMiYxrI1FyGgcPc3SXvRWCZivlhIAy?=
 =?us-ascii?Q?7XvEKsUxP+OWkuKy6ddb2mChg1lNCbuchw7JWNYupBbmpmwKJz+Q1JUIGWOF?=
 =?us-ascii?Q?/4e4L0wDyszFxuQcu5mEFYIAxnCHI4ZFnF5kvrE6kuCsbpdcxZSxVj0tkmYC?=
 =?us-ascii?Q?XK1CU02vZ0ZA3K1fOG5E06/BkPRJiMgIVCCpEmYyT5lBfpiycuAlYerTwBPC?=
 =?us-ascii?Q?hV3pheicupg2web1hL3km9E6TLH1+dgex7fienvijSakBlY7o9LfId/eeGx7?=
 =?us-ascii?Q?LYW9N93Pz3m12V3iHawWzGEVotwsYtm/mzfSiwZF1hv8v6oaJpR4DtWm74HV?=
 =?us-ascii?Q?AkKZosk9jadiEIfMkEo2vbJkpzYSdkl8YIlWiyEd6csKpYUx5fYy1bDPs1eM?=
 =?us-ascii?Q?DZxO5ctAXJpqk+Bswi8=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 4d41d750-81fb-4edb-b981-08d99ad9e80e
X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Oct 2021 12:44:54.3855
 (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: pj8naDd3dda/DY+F+z+qUZ4Jiv8bmq6BG9TYA8/Zv/pe5Q4Pyz/UP4PVTHL7AIrv
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5288
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Oct 29, 2021 at 11:15:31AM +1100, David Gibson wrote:

> > +Device must be bound to an iommufd before the attach operation can
> > +be conducted. The binding operation builds the connection between
> > +the devicefd (opened via device-passthrough framework) and IOMMUFD.
> > +IOMMU-protected security context is esbliashed when the binding
> > +operation is completed.
> 
> This can't be quite right.  You can't establish a safe security
> context until all devices in the groun are bound, but you can only
> bind them one at a time.

When any device is bound the entire group is implicitly adopted to
this iommufd and the whole group enters a safe-for-userspace state.

It is symmetrical with the kernel side which is also device focused,
when any struct device is bound to a kernel driver the entire group is
implicitly adopted to kernel mode.

Lu should send a patch series soon that harmonize how this works, it
is a very nice cleanup.

Jason