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([2a01:e0a:280:24f0:9db0:474c:ff43:9f5c]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42cc01a8ee7sm86671455e9.0.2024.09.12.01.45.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Sep 2024 01:45:06 -0700 (PDT) Message-ID: Date: Thu, 12 Sep 2024 10:45:05 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 15/17] vfio/migration: Multifd device state transfer support - receive side To: Avihai Horon , "Maciej S. Szmigiero" , Peter Xu Cc: Alex Williamson , Fabiano Rosas , Eric Blake , Markus Armbruster , =?UTF-8?Q?Daniel_P_=2E_Berrang=C3=A9?= , Joao Martins , qemu-devel@nongnu.org References: <4133ce80174fa3b81070adaeeb068554beba2854.1724701542.git.maciej.szmigiero@oracle.com> <12ebbb56-c2a7-42d0-8dad-9b459a490c39@nvidia.com> <5a9dba27-96e5-4404-b429-c36d9b1c5707@nvidia.com> Content-Language: en-US, fr From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= In-Reply-To: <5a9dba27-96e5-4404-b429-c36d9b1c5707@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.144, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 >>>> >>>> -    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING, >>>> - vbasedev->migration->device_state, errp); >>>> +    migration->load_bufs_thread_finished = false; >>>> +    migration->load_bufs_thread_want_exit = false; >>>> +    qemu_thread_create(&migration->load_bufs_thread, "vfio-load-bufs", >>>> +                       vfio_load_bufs_thread, opaque, QEMU_THREAD_JOINABLE); >>> >>> The device state save threads are manged by migration core thread pool. Don't we want to apply the same thread management scheme for the load flow as well? >> >> I think that (in contrast with the device state saving threads) >> the buffer loading / reordering thread is an implementation detail >> of the VFIO driver, so I don't think it really makes sense for multifd code >> to manage it. Is it an optimisation then ? In that case, could the implementation not use threads ? VFIO is complex, migration is complex, VFIO migration is even more. TBH, the idea of doing thread management in the VFIO subsystem makes me feel uncomfortable. Thanks, C.