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Tsirkin" , Markus Armbruster , Eric Blake , "Maciej S. Szmigiero" , Jason Wang , Ben Chaney , Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH RFC 0/2] migration/vl: new -incoming config:* for early migration parameters In-Reply-To: References: <20260528212947.368132-1-peterx@redhat.com> <87se7btcq9.fsf@suse.de> Date: Wed, 03 Jun 2026 14:56:41 -0300 Message-ID: <87ldcv7bja.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Action: no action X-Rspamd-Queue-Id: D08986AF09 X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; MISSING_XM_UA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MID_RHS_MATCH_FROM(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,gitlab.com:url,suse.de:mid,suse.de:dkim]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: 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 Peter Xu writes: > On Wed, Jun 03, 2026 at 06:15:57PM +0100, Daniel P. Berrang=C3=A9 wrote: >> On Wed, Jun 03, 2026 at 11:50:53AM -0400, Peter Xu wrote: >> > On Wed, Jun 03, 2026 at 10:48:54AM +0100, Daniel P. Berrang=C3=A9 wrot= e: >> > > On Fri, May 29, 2026 at 10:15:35AM -0400, Peter Xu wrote: >> > > > On Thu, May 28, 2026 at 07:01:50PM -0300, Fabiano Rosas wrote: >> > > > > Peter Xu writes: >> > > > >=20 >> > > > > > CI: https://gitlab.com/peterx/qemu/-/pipelines/2560168907 >> > > > > > >> > > > > > This series introduces a generic way to specify migration para= meters that >> > > > > > can be used even during the early boot phase of QEMU. >> > > > > > >> > > > > > One example use case that already existed is CPR-transfer / CP= R-exec. >> > > > > > currently QEMU has a temporary global variable (incoming_mode)= to achieve >> > > > > > this, but it's hard to understand and this hack bleeded into q= uite a few >> > > > > > places that we could have avoided. The lines in patch 2 touch= ed may >> > > > > > provide some idea. >> > > > > > >> > > > > > With a generic approach of setting migration parameters with c= mdlines, we >> > > > > > can remove this hack meanwhile QEMU should be able to keep the= CPR behavior >> > > > > > as before. To CPR maintainers and reviewers: please have a cl= oser look, >> > > > > > even better if it can be smoke tested, to see if this works fo= r Oracle's >> > > > > > environment, TIA. >> > > > > > >> > > > > > The 1st patch implemented that new semantics. It is straightf= orward: now >> > > > > > we can setup any migration parameter using an extra line of: >> > > > > > >> > > > > > -incoming config:key1=3Dvalue1,key2=3Dvalue2,... >>=20 >> snip >>=20 >> > > > > - using "config:" >> > > > >=20 >> > > > > This makes it non-uniform with uri and channels which don't have= a >> > > > > keyword in front of them. I guess I could live with it, but it s= eems >> > > > > odd. I see that it makes parsing way easier. >> > > >=20 >> > > > Yeah, having some identifier would be nice. I wished channels als= o have >> > > > identifiers if we don't need to keep compatibility. >> > >=20 >> > > IMHO having a magic "config:" prefix is an anti-pattern because it >> > > involves custom command line parsing logic. >> >=20 >> > Yes, it's not elegant. I wished we had something like this though when >> > introducing the cpr channels; right now anything wasn't "defer" or URI >> > implies it's a "channel".. >> >=20 >> > I also wanted to avoid introducing new cmdline parameters, so migration >> > incoming cmdlines can stick with the same option. If there's better >> > suggestion please shoot. >> >=20 >> > >=20 >> > > Does "-incoming config" imply '-incoming defer' semantics or is it >> > > independent ?=20=20 >> >=20 >> > They're independent. Examples: >> >=20 >> > a) "-incoming config:* -incoming tcp:*", setup parameters for TCP inc= oming >> > migration without further deferral >> >=20 >> > b) "-incoming config:*" only, setup global parameters for a possible >> > upcoming outgoing migration >>=20 >> In that case they should definitely be independent command line >> options. The old "-incoming" design is already broken / limited >> in the non-'defer' case because it is hardcoded to use URI syntax >> which can't express all the address formats we accept in QAPI >> syntax. Adding more special cases onto -incoming just makes the >> bad situation even worse and is not a forward looking design. >>=20 >> If we need the ability to specify migration parameters on the >> CLI, then as a starting point for the design, we should assume that >> -incoming does not exist, and design a complete solution from scratch >> that uses QAPI exclusively, both for addresses and configuration. > > Do we want to obsolete -incoming? > >>=20 >> As discussed before, IMHO the "migrate" and "migrate-incoming" >> commands need to accept both the address(s) and parameters/capabilities >> as inline data items rather than relying on pre-configured global state >> from the 'migrate-parameter' / 'migrate-capability' commands. > > This is one example that "relying only on migrate/migrate-incoming to > specify parameters" won't work. > > Essentially parameters like CPR's and the new "local" parameter wants to = be > global so that it will be visible and will have an impact on how other QE= MU > modules behave. Here for TAP when "local" is globally on we may want to > initialize the device differently from the default operations. That will > need to happen before any QMP commands. > >>=20 >> If we did that modelling for 'migrate-incoming' then that modelling of >> command parmaeters could map directly to a new '-migrate-incoming' >> command line argument that accepted exactly the same data model. > > This is true. Then we will make this series to depend on Fabiano's > previous work (to be posted; per we talked yesterday). > I don't see the dependency. Take the 'config' out from this series and pass a JSON into -incoming. It can be parsed into MigrationParameters all the same. > I wanted to see if we can reduce the impact to minimum, -incoming is inde= ed > not well designed, but in real life we have control over what can happen > with URIs and the current "config:" won't conflict with any of them. > > But if we strongly wish to obsolete -incoming completely, I'm OK too. > > Thanks,