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Fri, 12 Sep 2025 08:44:56 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHLW1odX3aZ/n3lLSGt/Q2HtgKjhuB3aEPNp+77FU6jUSBYcDBMHGuJF5YDscOaqCmA6Bk9vA== X-Received: by 2002:a05:6214:1c09:b0:727:e45a:562c with SMTP id 6a1803df08f44-767c5fc1237mr51504266d6.45.1757691896010; Fri, 12 Sep 2025 08:44:56 -0700 (PDT) Received: from x1.local ([174.89.135.121]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-763b6800370sm29280926d6.33.2025.09.12.08.44.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Sep 2025 08:44:55 -0700 (PDT) Date: Fri, 12 Sep 2025 11:44:43 -0400 From: Peter Xu To: Steven Sistare Cc: qemu-devel@nongnu.org, Fabiano Rosas , Markus Armbruster , Paolo Bonzini , Eric Blake , "Dr. David Alan Gilbert" , Vladimir Sementsov-Ogievskiy , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Subject: Re: [PATCH V3 0/9] Live update: cpr-exec Message-ID: References: <1755191843-283480-1-git-send-email-steven.sistare@oracle.com> <992bf553-e622-4e51-b1c7-f59c1413558e@oracle.com> <1a3c46b8-985e-4768-a3d1-e797370c0822@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1a3c46b8-985e-4768-a3d1-e797370c0822@oracle.com> 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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 Fri, Sep 12, 2025 at 10:50:34AM -0400, Steven Sistare wrote: > > > > How to guarantee src/dst device topology match > > > > exactly the same with the new cmdline? > > > > > > That is up to the mgmt layer, to know how QEMU was originally started, and > > > what has been hot plugged afterwards. The fast qom-list-get command that > > > I recently added can help here. > > > > I see. If you think that is the best way to consume cpr-exec, would you > > add a small section into the doc patch for it as well? > > It is not related to cpr-exec. It is related to hot plug, for any migration > type scenario, so it does not fit in the cpr-exec docs. IMHO it matters.. With cpr-transfer, QMP hot plugs works and will not contribute to downtime. cpr-exec also works, but will contribute to downtime. We could, in the comparison section between cpr-exec v.s. cpr-transfer, mention the potential difference on device hot plugs (out of many other differences), then also mention that there's an option to reduce downtime for cpr-exec due to hot-plug by converting QMP hot plugs into cmdlines leveraging qom-list-get and other facilities. From there we could further link to a special small section describing the usage of qom-list-get, or stop there. Thanks, -- Peter Xu