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Sat, 17 Apr 2021 11:33:24 +0200 (CEST) From: Markus Armbruster To: Eduardo Habkost Subject: Re: [PATCH RFC] migration: warn about non-migratable configurations unless '--no-migration' was specified References: <20210415154402.28424-1-vkuznets@redhat.com> <874kg68z07.fsf@vitty.brq.redhat.com> <20210416162801.zluqlbvyipoanedw@habkost.net> Date: Sat, 17 Apr 2021 11:33:24 +0200 In-Reply-To: <20210416162801.zluqlbvyipoanedw@habkost.net> (Eduardo Habkost's message of "Fri, 16 Apr 2021 12:28:01 -0400") Message-ID: <87tuo51cij.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Daniel P. =?utf-8?Q?Berrang?= =?utf-8?Q?=C3=A9?=" , Juan Quintela , qemu-devel@nongnu.org, "Dr. David Alan Gilbert" , Paolo Bonzini , Vitaly Kuznetsov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Eduardo Habkost writes: [...] > I would make live migration policy an enum, just to make sure > we are explicit about the requirements: > > - UNKNOWN: this is the current state in QEMU 6.0, where we don't > really know what the user expects. > This can be the default on existing versioned machine types, > just for compatibility. > I suggest making this print warnings for every migration > blocker (like this patch does). > I suggest deprecating this behavior as soon as we can. > > - PREFERRED: try to make the VM migratable when possible, but > don't print a warning or error out if migration is blocked. > This seems to be the behavior expected by libvirt today. > > - NOT_NEEDED: live migration is not needed, and QEMU is free to > enable features that block live migration or change guest ABI. > We can probably make this the default on machine types that > never supported live migration. > > - REQUIRED: live migration is required, and adding a migration > blocker would be a fatal error. To be precise: would be an error. During initial configuration, the error is fatal, i.e. exit(1). In a QMP command, it's not; only the command fails. > This is already implemented by --only-migratable. > I suggest making this the default on versioned machine types > after a few releases, and after deprecating UNKNOWN. Makes sense to me (but of course we can still quibble about the names).