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DIR:OUT; SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?y0XMlrL3UQBbJJqXssPKOQtxas1AWgb2SRV6cqCYiwF26KWqhRUomblprUjO?= =?us-ascii?Q?/nOTar+bZd7LfW17KyPE/bCNXil6xe+UUA7O7WmcPzxxVsvM3ytQf+TUsqyi?= =?us-ascii?Q?JgPMhwjoIoaBHp1v/wprAwfPiuXl2uUvVH1lVo+GrXgRdHxOIe+vZKNwHRa3?= =?us-ascii?Q?sDtmJQ857zKtW3Qfcb3z74mZVcEk0ka7qmKB6AX1fqI74tHl/xkVGYa3QEG6?= =?us-ascii?Q?4gc2/cg3/vI5Oih1CDPcmYRM+6txFcznztFEeI6mklLH8ic7ue725HrfP89e?= =?us-ascii?Q?mPUh+6SJC4DcXvgtLYfl/hEycFZgJAo1b8IZtE8px98FIusSDoYnEMR2Tm2K?= =?us-ascii?Q?NdyBI1nOoSrfoU2TJsyqXtWcgWFx7iQHKLb9O7iB5YK8Ev/QEHF9Ko7g1/I6?= =?us-ascii?Q?iSe9fWPOu6/enL1YxrNCDAoCsDYVXPqMhLA6pfxCxjbpAK9V6VZjTXeIvApG?= =?us-ascii?Q?11pf9rBDU+7NI1YvS+BD4t3aldS2ZueAXMeVIRum6EBEuGWxFOakfbw2FJfB?= =?us-ascii?Q?HSudR555v/v1iYgIzXSOjHTrtRuPxDsmtniGUBAhGEUKl4zPSdZipiRnFGGB?= =?us-ascii?Q?IqjHA8GImlI9V3xsKis8KifGS999alBB+bvjdIavXYBU/tN2jOKrVO1L4IUc?= =?us-ascii?Q?wlqvhbSOi2SYOOnbZDwES4ibzyBJJdk9VtY4jiVaJLeuSZjWUDVEGLZAGKLw?= =?us-ascii?Q?vtRz48dEQtWIt4JhX8qcx98/uRGdHBvw21kF1TBEVkNuDxp15PseUfdqQdny?= =?us-ascii?Q?d+oArEqCdUiW6I0UfpTAm508gfICpSii9kDKK0fojMFZJzIIsUAbK6Y3NwTC?= =?us-ascii?Q?L3Z06d5dlU9YE90oeFgvaxqmU8Q+lEQHKDFPouz5pvEReei41yg59WaTeUXU?= =?us-ascii?Q?xMFU4GsaS6KMUjBqGEpClVyWk6+D3wQslrWLpv6+H2bqFP/T4bqx8TFhYCc2?= =?us-ascii?Q?Gl7kS4dUqGAtNi2xlMlMha6mESmpgs7RZf8S7ZSqL0mgpHVAXUbAmN60xb5U?= =?us-ascii?Q?Eypxma5geiZIgeTOV7TYjF2ZKmrDxds3kk1rxgaMp/MX0U+oKLksSWceT3Wt?= =?us-ascii?Q?7ZBVUUAlJZhv5YzfRT/sPmmIOjVMj97AhyZxEOcAQVxnacikHMBqcpks8UJD?= =?us-ascii?Q?xIClTWyMgHAzPXecL2yGOOfhXoDxErOJtNJsl+NE1Cmd//Y1ExKmZ/4jhRbC?= =?us-ascii?Q?YwPVhjMi+IZYZ8dz6NAHwvxaVH6wxZn/1I7iin9W2C/4Oh1YauRDgcYk8kDy?= =?us-ascii?Q?C7YXEdQm+mIGUe0Zjq7j8C2R1iQilYOrfUtQUo2Amj3hHyrT5SdRUYB4VOMy?= =?us-ascii?Q?mXJlqziDncYiurziHOHVr8FthILd4KYsnJY+mD595U4rTBT7ChPEI+fjekzo?= =?us-ascii?Q?9YD6Hm/DNfoQjwkQ8zMrY8dTLqp+h4P6OsOVRzx/fnB5IlABGAHZJrCqro9J?= =?us-ascii?Q?QUXWz0hUj4OfubhJyTkVRP7/87UIoEx821mqpFAsU2mKoOzxIAy0fSYbntJe?= =?us-ascii?Q?YPStZY/huuUvIT3w7t9mVEr2GwjASfDQ43KiO+X0ykZnJeXqC3QgtVA0T8P/?= =?us-ascii?Q?FPh0TETZ0ZcTWESV0EaLSzGOcxbVF2kZWk5MEKymEXH3wqvKJ4WrVcNlwdg7?= =?us-ascii?Q?Bg=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 372fd061-e902-4b5d-ba66-08dab69fd285 X-MS-Exchange-CrossTenant-AuthSource: MWHPR11MB1629.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Oct 2022 15:44:37.8443 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: VJLgnu7pwOjEwat3be8t4d8XoQ9fD7xla70qxrbTX+XjBHEffNuLl5SrBM4JdGbINj605lE8zUfgMCxhJMy1D0iihW/Ezt7rRn1RC/kPb+w= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ1PR11MB6132 X-OriginatorOrg: intel.com X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Tue, Oct 25, 2022 at 05:33:31PM +0200, Maxime Coquelin wrote: > > > On 10/25/22 11:15, Hu, Jiayu wrote: > > > I think that for Vhost PMD, the Virtio completions should either be > > > performed by DMA engine or by a dedicated thread. > > > > We cannot depend on DMA engine to do completion, as there is no > > ordering guarantee on the HW. For example, given the DMA engine > > issues two updates on the used ring's index, it is possible that the second > > write completes before the first one. > > I'm not sure for Intel hardware, but other vendors may offer ordering > guarantees, it should be exposed as a capability of the DMA device. If > the DMA device offers this capability, it could be used for Vhost. > While I haven't been following this discussion, this particular comment caught my eye. For jobs submitted via a single dmadev device, the "FENCE" flag is provided as part of the dmadev API[1]. Obviously, if the writes come from different dmadevs, then things are rather more complicated. /Bruce [1] https://doc.dpdk.org/api/rte__dmadev_8h.html#a3375e7b956b305505073c4ff035afe2f