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Tsirkin" To: Anton Kuchin Cc: Stefan Hajnoczi , Vladimir Sementsov-Ogievskiy , qemu-devel@nongnu.org, yc-core@yandex-team.ru, "Dr. David Alan Gilbert" , Markus Armbruster , Eduardo Habkost , Juan Quintela , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Paolo Bonzini , virtio-fs@redhat.com, Eric Blake Subject: Re: [PATCH v3 1/1] vhost-user-fs: add migration type property Message-ID: <20230301102757-mutt-send-email-mst@kernel.org> References: <11593688-7ca4-def3-6212-7c26faa4d1c6@yandex-team.ru> <20230222121133-mutt-send-email-mst@kernel.org> <20230222151814-mutt-send-email-mst@kernel.org> <20230223023604-mutt-send-email-mst@kernel.org> <20230224034258-mutt-send-email-mst@kernel.org> <8611d901-0940-3747-c2cd-9c193c7f24f2@yandex-team.ru> <20230228094756-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@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 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, Feb 28, 2023 at 07:59:54PM +0200, Anton Kuchin wrote: > We can't rely here entirely on > destination to block this because if VM is migrated to file and then > can't be loaded by destination there is no way to fallback and resume > the source so we need to have some kind of blocker on source by default. So I commented about a fallback. IMO it's just orchestrator being silly: don't kill source qemu until you have made sure destination loaded the file, or re-load it, and all will be well. But a bigger issue that this highlights is simply that if migrating to file you have no idea at all where will the file be loaded. Maybe some orchestrators know but I don't see how we can be sure all of them know. The only time where we know whether the file is loaded on the same host where it was saved is when we actually load it. -- MST