* Dongli Zhang ([email protected]) wrote:
> 
> 
> On 2026-06-23 5:24 AM, Dr. David Alan Gilbert wrote:
> > * Dongli Zhang ([email protected]) wrote:
> >> Currently the cpr-transfer source QEMU instance cannot be driven entirely
> >> via HMP.  The source must use QMP in order to specify both the
> >> main migration channel and the CPR channel.
> >>
> >> Extend the HMP migrate command with an optional CPR channel URI. When the
> >> migration mode is cpr-transfer, HMP uses this URI to build a
> >> CPR MigrationChannel in addition to the main migration channel. The new
> >> argument is rejected unless the migration mode is cpr-transfer, so existing
> >> HMP migrate usage is unchanged.
> >>
> >> For example, source QEMU HMP commands can be something like below. The
> >> "unix:/tmp/cpr.sock" is for CPR URI.
> >>
> >> (qemu) migrate_set_parameter mode cpr-transfer
> >> (qemu) migrate tcp:0:50002 unix:/tmp/cpr.sock
> >>
> >> Signed-off-by: Dongli Zhang <[email protected]>
> > 
> > Yeh this looks OK to me; I don't see a check for if you do:
> > (qemu) migrate_set_parameter mode cpr-transfer
> > (qemu) migrate tcp:0:50002
> > 
> > Does that get caught by the qmp_migrate or should you add a check here?
> 
> I did test this before sending the patch.
> 
> With cpr-transfer mode enabled, missing the CPR channel is caught by
> migrate_channels_parse().
> 
> (qemu) migrate_set_parameter mode cpr-transfer
> (qemu) migrate tcp:0:50002
> Error: missing 'cpr' migration channel
> 
> ... including when the second uri is not a UNIX domain socket, reported by
> cpr_transfer_output().
> 
> (qemu) migrate tcp:0:50002 tcp:0:50003
> Error: bad cpr channel address; must be unix

OK, great.

> > 
> > I do have a slight preference for using flag optional parameters rather 
> > than positional, e.g.
> > 
> >    migrate -c unix:/tmp/cpr.sock tcp:0:50002
> > 
> > but I wouldn't insist on it.
> 
> I will follow this as Peter also voted for it.

Thanks - using a flag like that is much nicer, because it gets even harder
if someone wanted to add a 3rd path on in the future.

Dave

> Thank you very much!
> 
> Dongli Zhang
> 
> 
> 
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