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Thu, 13 Feb 2020 13:41:33 +0000 Date: Thu, 13 Feb 2020 09:41:28 -0400 From: Jason Gunthorpe To: Jason Wang Cc: mst@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, tiwei.bie@intel.com, maxime.coquelin@redhat.com, cunming.liang@intel.com, zhihong.wang@intel.com, rob.miller@broadcom.com, xiao.w.wang@intel.com, haotian.wang@sifive.com, lingshan.zhu@intel.com, eperezma@redhat.com, lulu@redhat.com, parav@mellanox.com, kevin.tian@intel.com, stefanha@redhat.com, rdunlap@infradead.org, hch@infradead.org, aadam@redhat.com, jiri@mellanox.com, shahafs@mellanox.com, hanand@xilinx.com, mhabets@solarflare.com Subject: Re: [PATCH V2 3/5] vDPA: introduce vDPA bus Message-ID: <20200213134128.GV4271@mellanox.com> References: <20200210035608.10002-1-jasowang@redhat.com> <20200210035608.10002-4-jasowang@redhat.com> <20200211134746.GI4271@mellanox.com> <20200212125108.GS4271@mellanox.com> <12775659-1589-39e4-e344-b7a2c792b0f3@redhat.com> Content-Type: text/plain; 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X-Forefront-PRVS: 031257FE13 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10009020)(4636009)(396003)(39860400002)(366004)(376002)(346002)(136003)(189003)(199004)(4744005)(86362001)(52116002)(81156014)(81166006)(8676002)(33656002)(1076003)(6916009)(7416002)(5660300002)(4326008)(186003)(66556008)(66476007)(9746002)(9786002)(26005)(2906002)(66946007)(36756003)(8936002)(2616005)(478600001)(316002)(24400500001);DIR:OUT;SFP:1101;SCL:1;SRVR:VI1PR05MB3358;H:VI1PR05MB4141.eurprd05.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A:1; Received-SPF: None (protection.outlook.com: mellanox.com does not designate permitted sender hosts) X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-MS-Exchange-AntiSpam-MessageData: idjbgiTTizyLnfS6MmeK1KvvFk71VaASvpgGsWtgJE6C79o/9XtsLAzVT7RiAa+7HGAmoImhLqzTaWDPUfdxJjyemQkojYdlzOAHijTy0m6CzI0/Gy7c49tBOuBL6SNbfD4RK0CAbUEHCCcK2BCopQ== X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: f1adcc69-d29a-477c-2237-08d7b08a7048 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Feb 2020 13:41:33.4454 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: llj4s6z4DgZNKv6H8eqtqYtCFHKU9j5ABavy0mshn4Hk0jLLN4OQR3CLCpxNmZYLQE5vOXFL3JrGS7SW6s3eYQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR05MB3358 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 13, 2020 at 11:34:10AM +0800, Jason Wang wrote: > > You have dev, type or > > class to choose from. Type is rarely used and doesn't seem to be used > > by vdpa, so class seems the right choice > > > > Jason > > Yes, but my understanding is class and bus are mutually exclusive. So we > can't add a class to a device which is already attached on a bus. While I suppose there are variations, typically 'class' devices are user facing things and 'bus' devices are internal facing (ie like a PCI device) So why is this using a bus? VDPA is a user facing object, so the driver should create a class vhost_vdpa device directly, and that driver should live in the drivers/vhost/ directory. For the PCI VF case this driver would bind to a PCI device like everything else For our future SF/ADI cases the driver would bind to some SF/ADI/whatever device on a bus. I don't see a reason for VDPA to be creating busses.. Jason