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Tsirkin" , Stefan Hajnoczi Cc: Cindy Lu , =?UTF-8?Q?Eugenio_P=c3=a9rez?= , qemu-devel@nongnu.org, maxime.coquelin@redhat.com References: <20230418151811.GA4048149@fedora> <20230418113320-mutt-send-email-mst@kernel.org> Content-Language: en-US From: Yajun Wu In-Reply-To: <20230418113320-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: KL1PR01CA0137.apcprd01.prod.exchangelabs.com (2603:1096:820:4::29) To DM4PR12MB5168.namprd12.prod.outlook.com (2603:10b6:5:397::8) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR12MB5168:EE_|PH8PR12MB7184:EE_ X-MS-Office365-Filtering-Correlation-Id: 6ee50b8d-f54e-4eeb-f654-08db4077d57b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; 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envelope-from=yajunw@nvidia.com; helo=NAM11-CO1-obe.outbound.protection.outlook.com X-Spam_score_int: -46 X-Spam_score: -4.7 X-Spam_bar: ---- X-Spam_report: (-4.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-2.597, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 4/18/2023 11:34 PM, Michael S. Tsirkin wrote: > On Tue, Apr 18, 2023 at 11:18:11AM -0400, Stefan Hajnoczi wrote: >> Hi, >> Cindy's commit ca71db438bdc ("vhost: implement vhost_dev_start method") >> added SET_STATUS calls to vhost_dev_start() and vhost_dev_stop() for all >> vhost backends. >> >> Eugenio's commit c3716f260bff ("vdpa: move vhost reset after get vring >> base") deferred the SET_STATUS 0 call in vhost_dev_stop() until after >> GET_VRING_BASE for vDPA only. In that commit Eugenio said, "A patch to >> make vhost_user_dev_start more similar to vdpa is desirable, but it can >> be added on top". >> >> I agree and think it's a good idea to keep the vhost backends in sync >> where possible. >> >> vhost-user still has the old behavior where QEMU sends SET_STATUS 0 >> before GET_VRING_BASE. Most existing vhost-user backends don't implement >> the SET_STATUS message, so I think no one has tripped over this yet. >> >> Any thoughts on making vhost-user behave like vDPA here? >> >> Stefan > Wow. Well SET_STATUS 0 resets the device so yes, I think doing that > before GET_VRING_BASE will lose a state. Donnu how it does not trip > up people, indeed the only idea is if people ignore SET_STATUS. > > > -- > MST For DPDK vhost-user backend SET_STATUS 0 (reset) is ignored. Yajun