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[70.24.86.62]) by smtp.gmail.com with ESMTPSA id b15-20020a05620a126f00b0075936b3026fsm1185794qkl.38.2023.05.19.08.31.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 May 2023 08:31:45 -0700 (PDT) Date: Fri, 19 May 2023 11:31:44 -0400 From: Peter Xu To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Wei Wang , quintela@redhat.com, lei4.wang@intel.com, qemu-devel@nongnu.org Subject: Re: [PATCH v1] migration: fail the cap check if it requires the use of deferred incoming Message-ID: References: <20230518160026.57414-1-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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_H2=-0.001, SPF_HELO_NONE=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 Fri, May 19, 2023 at 09:26:23AM +0100, Daniel P. Berrangé wrote: > On Thu, May 18, 2023 at 03:20:02PM -0400, Peter Xu wrote: > > On Fri, May 19, 2023 at 12:00:26AM +0800, Wei Wang wrote: > > > qemu_start_incoming_migration needs to check the number of multifd > > > channels or postcopy ram channels to configure the backlog parameter (i.e. > > > the maximum length to which the queue of pending connections for sockfd > > > may grow) of listen(). So multifd and postcopy-preempt caps require the > > > use of deferred incoming, that is, calling qemu_start_incoming_migration > > > should be deferred via qmp or hmp commands after the cap of multifd and > > > postcopy-preempt are configured. > > > > > > Check if deferred incoming is used when enabling multifd or > > > postcopy-preempt, and fail the check with error messages if not. > > > > > > Signed-off-by: Wei Wang > > > > IIUC this will unfortunately break things like: > > > > -global migration.x-postcopy-preempt=on > > > > where the cap is actually applied before incoming starts even with !defer > > so it should still work. > > > > Can we just make socket_start_incoming_migration_internal() listen on a > > static but larger value? > > Why do we need todo that ? I thought we just determined the problem was > a configuration error, not a code error. Yes, sorry I just read the other thread for more context. So it seems my concern wasn't really a concern anyway, now I'm fine with the current approach. Thanks, -- Peter Xu