On Tue, Nov 19, 2024 at 04:41:07PM -0500, Steven Sistare wrote:
> On 11/19/2024 4:29 PM, Peter Xu wrote:
> > On Tue, Nov 19, 2024 at 04:03:08PM -0500, Steven Sistare wrote:
> > > On 11/19/2024 3:51 PM, Peter Xu wrote:
> > > > On Tue, Nov 19, 2024 at 03:32:55PM -0500, Steven Sistare wrote:
> > > > > This begs the question, should we allow channels to be specified in
> > > > > hmp migrate
> > > > > commands and for -incoming, in a very simple way? Like with a prefix
> > > > > naming
> > > > > the channel. And eliminate the -cpr-uri argument. Examples:
> > > > >
> > > > > (qemu) migrate -d main:tcp:0:44444,cpr:unix:cpr.sock
> > > > >
> > > > > qemu -incoming main:tcp:0:44444,cpr:unix:cpr.sock
> > > > > qemu -incoming main:defer,cpr:unix:cpr.sock
> > > >
> > > > IMHO keeping the old syntax working would still be nice to not break
> > > > scripts.
> > >
> > > The channel tag would be optional, so backwards compatible. Its
> > > unambiguous
> > > as long as the channel names are not also protocol names.
> >
> > Ah that's ok then. Or maybe use "="?
> >
> > "main=XXX,cpr=XXX"
> >
> > Then if no "=" it's the old?
>
> Sure, that works.
>
> > > > I was thinking we could simply add one more parameter for taking
> > > > cpr uri, like:
> > > >
> > > > {
> > > > .name = "migrate",
> > > > .args_type = "detach:-d,resume:-r,uri:s,cpr:s?",
> > > > .params = "[-d] [-r] uri [cpr_uri]",
> > > > .help = "migrate to URI (using -d to not wait for
> > > > completion)"
> > > > "\n\t\t\t -r to resume a paused postcopy
> > > > migration",
> > > > "\n\t\t\t Setup cpr_uri to migrate with
> > > > cpr-transfer",
> > > > .cmd = hmp_migrate,
> > > > },
> > >
> > > That's fine.
> > >
> > > I do like the incoming syntax, though, instead of -cpr-uri. What do you
> > > think?
> >
> > That'll definitely be lovely if possible, though would any monitor be alive
> > at all before taking a cpr stream, with this series alone? I thought you
> > dropped the precreate, then QEMU isn't able to run the monitor loop until
> > cpr-uri is loaded.
>
> No monitor or precreate changes. I would parse -incoming, extract and use
> the cpr
> channel early, and use the main channel later as usual. It's just a
> different way of
> specifying cpr-uri. I like it because the specification language is more
> consistent,
> referring to a "cpr channel" both on the outgoing and incoming side:
>
> This mode requires a second migration channel named "cpr", included in
> the channel arguments of the migrate command on the outgoing side, and
> in the QEMU -incoming parameter on the incoming side. The channel must
> be a type, such as unix socket, that supports SCM_RIGHTS.
Ah, that's ok at least to me. I hope defer could still work (for Libvirt),
though. Probably something like main=defer,cpr=XXX.
--
Peter Xu
