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[99.254.114.190]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d43812ad15sm63046d6.84.2024.11.19.12.16.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Nov 2024 12:16:58 -0800 (PST) Date: Tue, 19 Nov 2024 15:16:56 -0500 From: Peter Xu To: Steven Sistare Cc: qemu-devel@nongnu.org, Fabiano Rosas , David Hildenbrand , Marcel Apfelbaum , Eduardo Habkost , Philippe Mathieu-Daude , Paolo Bonzini , "Daniel P. Berrange" , Markus Armbruster Subject: Re: [PATCH V3 11/16] migration: cpr-transfer mode Message-ID: References: <1730468875-249970-1-git-send-email-steven.sistare@oracle.com> <1730468875-249970-12-git-send-email-steven.sistare@oracle.com> <51967cb2-05ec-485b-a639-8ff58d565604@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.14, 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=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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, Nov 19, 2024 at 02:50:40PM -0500, Steven Sistare wrote: > On 11/14/2024 2:04 PM, Peter Xu wrote: > > On Thu, Nov 14, 2024 at 01:36:00PM -0500, Steven Sistare wrote: > > > On 11/13/2024 4:58 PM, Peter Xu wrote: > > > > On Fri, Nov 01, 2024 at 06:47:50AM -0700, Steve Sistare wrote: > > > > > Add the cpr-transfer migration mode. Usage: > > > > > qemu-system-$arch -machine anon-alloc=memfd ... > > > > > > > > > > start new QEMU with "-incoming -cpr-uri " > > > > > > > > > > Issue commands to old QEMU: > > > > > migrate_set_parameter mode cpr-transfer > > > > > migrate_set_parameter cpr-uri > > > > > migrate -d > > > > > > > > QMP command "migrate" already allows taking MigrationChannel lists, cpr can > > > > be the 2nd supported channel besides "main". > > > > > > > > I apologize on only noticing this until now.. I wished the incoming side > > > > can do the same already (which also takes 'MigrationChannel') if monitors > > > > init can be moved earlier, and if precreate worked out. If not, we should > > > > still consider doing that on source, because cpr-uri isn't usable on dest > > > > anyway.. so they need to be treated separately even now. > > > > > > > > Then after we make the monitor code run earlier in the future we could > > > > introduce that to incoming side too, obsoleting -cpr-uri there. > > > > > > I have already been shot down on precreate and monitors init, so we are > > > left with specifying a "cpr" channel on the outgoing side, and -cpr-uri > > > on the incoming side. That will confuse users, will require more implementation > > > and specification work than you perhaps realize to explain this to users, > > > > What is the specification work? Can you elaborate? > > > > > and only gets us halfway to your desired end point of specifying everything > > > using channels. I don't like that plan! > > > > > > If we ever get the ability to open the monitor early, then we can implement > > > a complete and clean solution using channels and declare the other options > > > obsolete. > > > > The sender side doesn't need to wait for destination side to be ready? > > Dest side isn't a reason to me on how we should make sender side work if > > they're totally separate anyway. Dest requires -cpr-uri because we don't > > yet have a choice. > > > > Is the only concern about code changes? I'm expecting this change is far > > less controversial comparing to many others in this series, even if I > > confess that may still contain some diff. They should hopefully be > > straightforward, unlike many of the changes elsewhere in the series. > > > > If you prefer not writting that patch, I am OK, and I can write one patch > > on top of your series after it lands if that is OK for you. I still want to > > have this there when release 10.0 if I didn't misunderstood anything, so > > I'll be able to remove cpr-uri directly in that patch too. > > I made the changes: > * implementation > * documentation in CPR.rst and QAPI > * convert sample code in CPR.rst, commit messages, and cover letter to QMP, > because a channel cannot be specified using HMP. Yeah we can leave HMP as of now; it can easily be added on top with existing helpers like migrate_uri_parse(). > * migration tests > > New CPR.rst: > > ------------------- > ... > This mode requires a second migration channel named "cpr" in the > channel arguments on the outgoing side. The channel must be a type, > such as unix socket, that supports SCM_RIGHTS. However, the cpr > channel cannot be added to the list of channels for a migrate-incoming > command, because it must be read before new QEMU opens a monitor. > Instead, the user passes the equivalent URI for the channel as part of > the ``cpr-uri`` command-line argument to new QEMU. > ... > > Outgoing: Incoming: > > # qemu-kvm -qmp stdio > -object memory-backend-file,id=ram0,size=4G, > mem-path=/dev/shm/ram0,share=on -m 4G > -machine aux-ram-share=on > ... > # qemu-kvm -monitor stdio > -incoming tcp:0:44444 > -cpr-uri unix:cpr.sock > ... > {"execute":"qmp_capabilities"} > > {"execute": "query-status"} > {"return": {"status": "running", > "running": true}} > > {"execute":"migrate-set-parameters", > "arguments":{"mode":"cpr-transfer"}} > > {"execute": "migrate", "arguments": { "channels": [ > {"channel-type": "main", > "addr": { "transport": "socket", "type": "inet", > "host": "0", "port": "44444" }}, > {"channel-type": "cpr", > "addr": { "transport": "socket", "type": "unix", > "path": "cpr.sock" }}]}} > > QEMU 9.2.50 monitor > (qemu) info status > VM status: running > > {"execute": "query-status"} > {"return": {"status": "postmigrate", > "running": false}} > ------------------- Thank you, Steve! -- Peter Xu