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Fri, 24 Jul 2020 00:19:35 +0000 Date: Thu, 23 Jul 2020 21:19:30 -0300 From: Jason Gunthorpe To: "Tian, Kevin" Cc: "Jiang, Dave" , "vkoul@kernel.org" , "Dey, Megha" , "maz@kernel.org" , "bhelgaas@google.com" , "rafael@kernel.org" , "gregkh@linuxfoundation.org" , "tglx@linutronix.de" , "hpa@zytor.com" , "alex.williamson@redhat.com" , "Pan, Jacob jun" , "Raj, Ashok" , "Liu, Yi L" , "Lu, Baolu" , "Kumar, Sanjay K" , "Luck, Tony" , "Lin, Jing" , "Williams, Dan J" , "kwankhede@nvidia.com" , "eric.auger@redhat.com" , "parav@mellanox.com" , "Hansen, Dave" , "netanelg@mellanox.com" , "shahafs@mellanox.com" , "yan.y.zhao@linux.intel.com" , "pbonzini@redhat.com" , "Ortiz, Samuel" , "Hossain, Mona" , "dmaengine@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "linux-pci@vger.kernel.org" , "kvm@vger.kernel.org" Subject: Re: [PATCH RFC v2 00/18] Add VFIO mediated device support and DEV-MSI support for the idxd driver Message-ID: <20200724001930.GS2021248@mellanox.com> References: <159534667974.28840.2045034360240786644.stgit@djiang5-desk3.ch.intel.com> <20200721164527.GD2021248@mellanox.com> Content-Type: text/plain; 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X-Microsoft-Antispam-Message-Info: kn+1XU7PKTZVibxyduX59TPZGAoBiXIRju/TovbE96He8qJHDj80MZt1uRIs4e6U595f4h79TZn0qgk4RC3zAeLkpz5hF8SNqQ8iksfagpukJCZXs+P3lwHJVuQUy37PvOQ2uDet8IOuu2jnlqCH2+AetwERtBVaZjuFXL8iRF0ibbCYecgWu5DA8TA2ENMK9dKF0Z1O5sC+22CI/Mk5XvfHNvb9KgnPY1g/dOdDiXd7mpsPPmqXxoWfzd8xhqvVReUUPNI6Y7fPWyfOKsbNpuq0yhmWbFYIoEotvKUBuAQ7tPsvK/Gh0FhEkcAL6j0B9MLFgAB4pyHKVf3H96R3OA== X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR05MB4141.eurprd05.prod.outlook.com;PTR:;CAT:NONE;SFTY:;SFS:(4636009)(376002)(396003)(366004)(346002)(136003)(39860400002)(33656002)(26005)(6916009)(5660300002)(4326008)(36756003)(9746002)(9786002)(1076003)(7406005)(66476007)(186003)(7416002)(478600001)(2906002)(2616005)(426003)(86362001)(8676002)(66946007)(54906003)(66556008)(316002)(8936002);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData: pqhcNQMSuLcBz0D1S/zT5wggPgEbWSbmN4ICtH/pXZ3e6nw6HDQGe3XNxLiALdRG/d3qQMfzsjGoa/SkjwjHhPjbhlCsQi/qmyWfOg4MRXataK9h76zcdAHdsUTcB3Q2DLQ3BIjoFnGq4Co2P0A4b3CKPga9dig3+ECLE+8f7VMCE+8fgFhK5DnrZKIC9Uq24OCV21P6cFAyEYuhl+SxDlvOQEhFxj6pyNyVi11eLbnqk9gpqHGEnxcSFj3aPPPrpWp+4lN4iUR3w8JizdwDPAMyCxTYQFw7Gm2ZJiZbHJdRg6rTiwmsL/kiZJ9551Cd5rv9ri/k78GvVvUp22Mmk/E2DDAopL6ngESoqHohcklnZ9t+n+ONFFnJgdkY+4EdScCI4pWo3UDB645PnUKrFbOVnOfA41SNs9tkgLeVy/kl6KbjDCjQx2WvusIJSDmavYsRJ9L7uCgWpWkJ+FT22aAwdS87Yp6sj2j0UyEvYX8= X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-Network-Message-Id: 806467bc-1a4b-4a0a-a658-08d82f673e69 X-MS-Exchange-CrossTenant-AuthSource: VI1PR05MB4141.eurprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 Jul 2020 00:19:35.1871 (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: 9UHQLJZXe5XZN5s7IhMkNzkltN0nXje4Fgdkes6OT0LvBJQPNOvVoYs7zRc/YhIWh8NZks6c4LU2+eFPmdRvoQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR0502MB3951 Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On Tue, Jul 21, 2020 at 11:54:49PM +0000, Tian, Kevin wrote: > In a nutshell, applications don't require raw WQ controllability as guest > kernel drivers may expect. Extending DSA user space interface to be another > passthrough interface just for virtualization needs is less compelling than > leveraging established VFIO/mdev framework (with the major merit that > existing user space VMMs just work w/o any change as long as they already > support VFIO uAPI). Sure, but the above is how the cover letter should have summarized that discussion, not as "it is not much code difference" > In last review you said that you didn't hard nak this approach and would > like to hear opinion from virtualization guys. In this version we CCed KVM > mailing list, Paolo (VFIO/Qemu), Alex (VFIO), Samuel (Rust-VMM/Cloud > hypervisor), etc. Let's see how they feel about this approach. Yes, the VFIO community should decide. If we are doing emulation tasks in the kernel now, then I can think of several nice semi-emulated mdevs to propose. This will not be some one off, but the start of a widely copied pattern. Jason