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Fri, 3 Jul 2020 16:26:32 +0000 (UTC) Date: Fri, 3 Jul 2020 17:26:30 +0100 From: "Dr. David Alan Gilbert" To: Peter Krempa Subject: Re: [PATCH 2/6] migration: introduce savevm, loadvm, delvm QMP commands Message-ID: <20200703162630.GJ6641@work-vm> References: <20200702175754.2211821-1-berrange@redhat.com> <20200702175754.2211821-3-berrange@redhat.com> <20200702182452.GP1888119@redhat.com> <20200703154933.GE6641@work-vm> <20200703160235.GM2213227@redhat.com> <20200703161012.GH6641@work-vm> <20200703162417.GA3255981@angien.pipo.sk> MIME-Version: 1.0 In-Reply-To: <20200703162417.GA3255981@angien.pipo.sk> User-Agent: Mutt/1.14.5 (2020-06-23) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/03 03:17:33 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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: Kevin Wolf , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , qemu-block@nongnu.org, Juan Quintela , Markus Armbruster , qemu-devel@nongnu.org, Max Reitz , Pavel Dovgalyuk , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Krempa (pkrempa@redhat.com) wrote: > On Fri, Jul 03, 2020 at 17:10:12 +0100, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > > On Fri, Jul 03, 2020 at 04:49:33PM +0100, Dr. David Alan Gilbert wrote: > > > > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > > > > On Thu, Jul 02, 2020 at 01:12:52PM -0500, Eric Blake wrote: > > > > > > On 7/2/20 12:57 PM, Daniel P. Berrangé wrote: > > [...] > > > > > Remind me, what was the problem with just making a block: migration > > > > channel, and then we can migrate to it? > > > > > > migration only does vmstate, not disks. The current blockdev commands > > > are all related to external snapshots, nothing for internal snapshots > > > AFAIK. So we still need commands to load/save internal snapshots of > > > the disk data in the qcow2 files. > > > > > > So we could look at loadvm/savevm conceptually as a syntax sugar above > > > a migration transport that targets disk images, and blockdev QMP command > > > that can do internal snapshots. Neither of these exist though and feel > > > like a significantly larger amount of work than using existing functionality > > > that is currently working. > > > > I think that's what we should aim for; adding this wrapper isn't gaining > > that much without moving a bit towards that; so I would stick with the > > x- for now. > > Relying on the HMP variants is IMO even worse. Error handling is > terrible there. I'd vote even for a straight wrapper without any logic > at this point. IMO it's just necessary to document that it's an > intermediate solution which WILL be deprecated and removed as soon as a > suitable replacement is in place. > > Not doing anything is the argument we hear for multiple years now and > savevm/delvm/loadvm are now the only 3 commands used via the HMP wrapper > in libvirt. > > Since deprecation is now a thing I think we can add a disposable > inteface. In the end HMP will or will not need to remain anyways and the > deprecation there is IMO less clear. Only if we come up with a list of what we actually need to do to properly fix it; I'm not suggesting we actually need to do the work, but we should figure out what we need to do. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK