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Wed, 11 Mar 2026 10:42:28 -0700 (PDT) Date: Wed, 11 Mar 2026 13:42:26 -0400 From: Peter Xu To: Fabiano Rosas Cc: luzhipeng , qemu-devel@nongnu.org, Eric Blake , Markus Armbruster Subject: Re: [PATCH] qmp: Add ram-block-set/get-migratable commands Message-ID: References: <20260311100116.984-1-luzhipeng@cestc.cn> <87ldfyzg66.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87ldfyzg66.fsf@suse.de> 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: -3 X-Spam_score: -0.4 X-Spam_bar: / X-Spam_report: (-0.4 / 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=0.819, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.903, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development 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 Wed, Mar 11, 2026 at 09:47:29AM -0300, Fabiano Rosas wrote: > luzhipeng writes: > > > Introduce two new QMP commands to manage RAMBlock migratable state: > > 1. ram-block-set-migratable: Dynamically set a RAMBlock's migratable state > > 2. ram-block-get-migratable: Query a RAMBlock's migratable state > > > > Hi! Could you provide more information on what are the use-cases for the > new commands? > > In particular, what is the condition that can cause a ramblock to become > migratable/unmigratable at runtime that cannot be detected by QEMU > itself? Or instead of saying "detected" maybe it's "decided" by QEMU. The QEMU cmdline and rest (e.g. a set of QMP commands to create the devices that needs to happen on both sides, or migration caps/params like x-ignore-shared) normally decides whether a ramblock should be migrated, and AFAIU that's part of the guest ABI. I think it may make more sense if we want to avoid migrating some ramblocks then we provide some similar way (e.g. a object property of the memory backend) rather than allowing it to be flipped anytime, causing more unpredictable guest ABI. Thanks, -- Peter Xu