Date:   Mon, 6 Dec 2021 11:06:47 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Lu Baolu <baolu.lu@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Joerg Roedel <joro@8bytes.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Dan Williams <dan.j.williams@intel.com>, rafael@kernel.org,
        Diana Craciun <diana.craciun@oss.nxp.com>,
        Cornelia Huck <cohuck@redhat.com>,
        Eric Auger <eric.auger@redhat.com>,
        Liu Yi L <yi.l.liu@intel.com>,
        Jacob jun Pan <jacob.jun.pan@intel.com>,
        Chaitanya Kulkarni <kch@nvidia.com>,
        Stuart Yoder <stuyoder@gmail.com>,
        Laurentiu Tudor <laurentiu.tudor@nxp.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Li Yang <leoyang.li@nxp.com>,
        Dmitry Osipenko <digetx@gmail.com>,
        iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 04/18] driver core: platform: Add driver dma ownership
 management
Message-ID: <20211206150647.GE4670@nvidia.com>
References: <20211206015903.88687-1-baolu.lu@linux.intel.com>
 <20211206015903.88687-5-baolu.lu@linux.intel.com>
 <Ya4f662Af+8kE2F/@infradead.org>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Ya4f662Af+8kE2F/@infradead.org>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?rFBCOmDC9Xk7KxqnGPh0ccDa7pLqkktG2NSwSRn/Fz8GHYeSus91M/2TvS96?=
 =?us-ascii?Q?OJ+dEotJgFgM5S9ub2YsudhQGQDlLBDLDJ8Gt4blAW/Ur3A2IBdyWO2DknRt?=
 =?us-ascii?Q?CA56U2lsK/jOE4jmcGVT0/1qD2iuY/WoXw3yUrZN0/slbbzlgZFmd9Itw/am?=
 =?us-ascii?Q?DFo6fW37aPCFmE8xt7BUYxxllXeJN7fQvYFE7ULg/cDBQUF8Xa43N+haLeSv?=
 =?us-ascii?Q?D9m5f5wBggv8QQofhHCLz5Cf8Xrug8u6syFPBPEYCZBYbLtQVvuQbMCzyYle?=
 =?us-ascii?Q?2Uc8U9KhygS2HgXP7DZc+6UjmEPvJdYSji+QPbpW01B3oACPeW0L4eXRTm57?=
 =?us-ascii?Q?KA7/M8Y1oTYtcpiMdY/yShHX9pUisXLCBllXjty/HdTaqn0bPDtDzBlwwdXb?=
 =?us-ascii?Q?U1wUgusFSrWFgKyKoSd6YmhkyavvGKx50mCXyvRiSlgkRWYvCCtagX7YywRl?=
 =?us-ascii?Q?JdLQdhu5HFSdwA3IJea9vO1F2Kb798xCyjLaXxkLPMA+n2GLEJmNDx045/7v?=
 =?us-ascii?Q?kRNp1B31jfkV1bhNcvF6d/KSgU9xW2Ep63nNbPgLMys3MBH86FDNcZARgl3F?=
 =?us-ascii?Q?orZwOqS88P4MLQPXN0n8iaq3madBd5kDBum3eoVJXANpP90Jq757t59GgJ2H?=
 =?us-ascii?Q?+bHoOy9fUrciNRk/z17MCkHIO/IVRv2KyoOSvlYR2dEmjbdAPXZ3cSOlqeza?=
 =?us-ascii?Q?SZaqgCPDavwNcr7YjsGwXANSmU2LOEoBOGA/Rr+itBj+DFFbszC1kN/1QBMY?=
 =?us-ascii?Q?YnaEj4nMz1t1zI1MES/VlfMRC6gRjJvlERL4ZldeQOvoABZKQaCMFyUb4efG?=
 =?us-ascii?Q?PACHnpOY6MhvpC23ALadS9x7GOu9qzR/xIasDMIf4J1MazMiCYTCuu4J0adK?=
 =?us-ascii?Q?4ngSJwiRTnK4n/ub/htflPR1tRw0MUVhA+5KHMRF3vnYuoj/RgGqxAEqmvSU?=
 =?us-ascii?Q?4UwPT2iq/gSSE05B6bTp+Q0wY6PQBSMu2hMLIJmVFVdAyzXbE4nwIBLxUa2W?=
 =?us-ascii?Q?eCKriAaUluL/ldzPAs6/I5ix6nH8+NC2cuVK9uTgACdtTK/FUj7wocTtr23Z?=
 =?us-ascii?Q?3eG6NIqgYXh8fRltGEikuEouWCyX395GhSTBYaegUhvCcaFtvg7hVaudzobl?=
 =?us-ascii?Q?GKm2mXl73uKZZMF2SpZlmuzBLeOliE7z7TLP78YSsG7hYJl9jK+OAMW+lOuH?=
 =?us-ascii?Q?vwXn4xwBUfgx5iwxQUHCyMGGkY3j7tsWq7Jw+CHBLrUiaUdUGtUMetu29suq?=
 =?us-ascii?Q?ILz5VY14eAWN12XSCV+uXMU5uz9x++DgXfDOmWQ5I6KlWhub9AxzbN6NJZqz?=
 =?us-ascii?Q?AzhqUhBC7KRUB3evyGbx1+904Py96t03cuDkWbVAYcMvplzmnUGPXLh6Nw3y?=
 =?us-ascii?Q?gpCnlMZVbEe047+ijwefVe55Y88hd+NPrUiHoXT8ScTOSyV119+0n5+lwjlY?=
 =?us-ascii?Q?C4darY2nsMkGPeaIfpr3z8BRTCHoQdO7HeV0oUXNivgc/3FQ1GRgSyu00rPt?=
 =?us-ascii?Q?RsKtGR/OIKlUgEDYCdVniiOpzBU6NoasExY8YmGOMSo0NQfK0xI3XtdacbLh?=
 =?us-ascii?Q?rcbr84zHXhxlz60psuk=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: cfba5c46-e1ad-454c-a5ad-08d9b8ca06c0
X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Dec 2021 15:06:48.8341
 (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: g85Z5i4QYonz2nVRKPWrBPZbgVzIJARtEwySs4vhM9OPX6Om2do66c7bHwGqBJp4
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5237
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Dec 06, 2021 at 06:36:27AM -0800, Christoph Hellwig wrote:
> I really hate the amount of boilerplate code that having this in each
> bus type causes.

+1 

I liked the first version of this series better with the code near
really_probe().

Can we go back to that with some device_configure_dma() wrapper
condtionally called by really_probe as we discussed?

> Between that and the suggestion from Joerg I wonder if we could do the
> following again:
> 
>  - add new no_kernel_dma flag to struct device_driver
>  - set this flag for the various vfio drivers
>  - skip claiming the kernel dma ownership for those (or rather release
>    it if the suggestion from Joerg works out)

v1 did exactly this.

Jason