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Tue, 02 Apr 2024 14:43:51 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGZ2x7wc/CsufYG8HdeQyJIKY/pZMujHRCMIEAzmpl2VfYME6CCE5ZV5pSGnTQo3rA+kX6ufQ== X-Received: by 2002:a05:6870:1d1:b0:22e:7040:6fd with SMTP id n17-20020a05687001d100b0022e704006fdmr2778716oad.3.1712094231140; Tue, 02 Apr 2024 14:43:51 -0700 (PDT) Received: from x1n ([99.254.121.117]) by smtp.gmail.com with ESMTPSA id ez6-20020a05622a4c8600b0043146d55f0csm5890370qtb.60.2024.04.02.14.43.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Apr 2024 14:43:50 -0700 (PDT) Date: Tue, 2 Apr 2024 17:43:48 -0400 From: Peter Xu To: "Wang, Wei W" Cc: "Wang, Lei4" , "qemu-devel@nongnu.org" , "farosas@suse.de" Subject: Re: [PATCH] migration: Yield coroutine when receiving MIG_CMD_POSTCOPY_LISTEN Message-ID: References: <20240329033205.26087-1-lei4.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=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 On Tue, Apr 02, 2024 at 07:20:01AM +0000, Wang, Wei W wrote: > > IIUC we still need that pre_7_2 stuff and keep the postponed connect() to > > make sure the ordering is done properly. Wei, could you elaborate the patch > > you mentioned? Maybe I missed some spots. > > Sure. I saw your patch (5655aab079) ensures that the preempt channel to be > created when PONG is received from the destination, which indicates that > the main channel has been ready on the destination side. > > Why was it decided to postpone the preempt channel's connect() for newer QEMU > only? The old QEMU (before 7.2) still performs preempt channel connect() in > migrate_fd_connect(), doesn't it have the disordering issue? Yes it has, but the solution actually was not compatible with older binaries, so migration was broken back then.. See: https://lore.kernel.org/qemu-devel/20230326172540.2571110-1-peterx@redhat.com/ My memory was that we didn't have a good solution to fix it without breaking the old protocol, so it can only be fixed on newer binaries. Thanks, -- Peter Xu