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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?nQ4q6H52DyRkLCKNY/KXfnl5EP2zwhJ6jH32DI9Nj/ZVwpQLuChgvK1gY/fC?= =?us-ascii?Q?edJ0mSWL52Pj86TBA+UdIiUfQoXm/AOD7G7hCrqLtseEwNsQENgthTki67lh?= =?us-ascii?Q?XEGyslY3B0MFioPwCLEsRkTm+xA5m/UmjNvpfp+2STe4Q9gLEK0Ze+Ptl+JX?= =?us-ascii?Q?6SufwppBBYMImgP53bzUn1qA2x1NdUVBY+x07i9bJ6feT/1U+toh3rHDIPn9?= =?us-ascii?Q?F6+JThzTWyEXcb0cPg1Zq3mqmMoT4bfQMHnz359DmSEYr+c7Xm7xYRyhAeAg?= =?us-ascii?Q?NXZ/snfacJEPFzsyvgYr42ZT/zYRH0D+SpME6Y4KLkmTQDJ79rBCdpx9EGF+?= =?us-ascii?Q?GrHJyxRe5QK6IG7SM564QM+b2yS4P3l6gJZ9cv57uuwJLax6/WPiF4lqoRYQ?= =?us-ascii?Q?PB+VekmKjgoZzbV7c19WE6BvjBhIBJNRVmRzNpGj4tF/ekgSBWOnGG3r10Gf?= =?us-ascii?Q?/DhZfVqDLxIPmP43Y/AsgQjrrffElqqDOGE8GU4wbsy/PnB/DdeYus16nNas?= =?us-ascii?Q?br5j1ranKngmNw4ObjqWcJqYv3PvgDc+rMuZjLGjlQYWcPddt/zPbxqNEqmp?= =?us-ascii?Q?9dBNkc24EMgpiyPijUlv2sm8Ns3ed4G47mJPxwB7nFKHN63nySk3TempbFQg?= =?us-ascii?Q?oArrRDJyoiulxfsPVZkz0wheLR58GU01g/QoaRJasD0wlBgU0+hn4SPDizu/?= =?us-ascii?Q?zxaZ6+Zg90vsKtK2yEcZ1zYgluFjFqRMon3/tb+uywuxjOqDW2J43AVscbKa?= =?us-ascii?Q?1S/QQaE/CWnaykAPsPTuVV2vN4PyBIeryrrTyrgl01Gzj6KJc+tLiZ67NiyF?= =?us-ascii?Q?upOj4W6FhYZwMpAKRoygfVoIt+gTvwhBGa84MCxOf9YIV0J4EZtTMa/GCEt4?= =?us-ascii?Q?FsDjg5da3OBlU2DxnywORgaFQovqfOzozZgMrRgsbaLQu6/tdJbRcCTetzue?= =?us-ascii?Q?EwWA3qIExaRf+/vLykUajJgE3lLG4coysHF7IQhenUW7/l5lNwp5dy6+JXBu?= =?us-ascii?Q?Y/CYdLME3bSPr1Audgvhc9nKYEJcZbbjJeWs5p8I16R/G+/QzR8dq/fwg9eB?= =?us-ascii?Q?vKlJrJpPkyScOydW9wknE4gU7SN33kqLE5jPGc8mVSmVIGJzQyXAP9xcaGFa?= =?us-ascii?Q?/NB8A6FCCjwwTxbebRYG+nB8bHi9MF2009XOnaPKvXxjsgiISUL80lRrpx1+?= =?us-ascii?Q?FkMK4bax2d14kFsu0yBrW8CRQ8lm0e67C5klQ0dFC9rRvFADufyU0q4KcoPo?= =?us-ascii?Q?3OvcOzjHchqPP/Eupf20OiA9612FlyKQlPISx8oxpePfEbr5/cW7buSujE3s?= =?us-ascii?Q?kBtmR7x5GMk8xc+CLJbyPvjO?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: b6d409bb-7fea-4be2-e857-08d92a7c35d7 X-MS-Exchange-CrossTenant-AuthSource: BL0PR12MB5506.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jun 2021 12:52:01.8762 (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: XZtksV2SvZfOICVCA8oUIfSpCmSiS7vwuxjpJ2dfxAkWw51Ompmn+5Vh88Vj/mfz X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL1PR12MB5078 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 08, 2021 at 10:54:59AM +0200, Enrico Weigelt, metux IT consult wrote: > Maybe the device as well as the transport could announce their > capability (which IMHO should go via the virtio protocol), and if both > are capable, the (guest's) virtio subsys tells the driver whether it's > usable for a specific device. Perhaps we should also have a mechanism > to tell the device that it's actually used. The usage should be extremely narrow, like "If the driver issues a GPU command with flag X then the resulting DMAs will be no-snoop and the driver must re-establish coherency at the right moment" It is not a general idea, but something baked directly into the device protocol that virtio carries. The general notion of no-nsoop should ideally be carried in the PCIe extended config space flag. If 0 then no-snoop should never be issued, expected, or requested. Jason