Re: [RFC V1 0/6] Live update: cpr-transfer

[Peter Xu]

On Sat, Jul 20, 2024 at 04:07:50PM -0400, Steven Sistare wrote:
> > > The new user-visible interfaces are:
> > >    * cpr-transfer (MigMode migration parameter)
> > >    * cpr-uri (migration parameter)
> > 
> > I wonder whether this parameter can be avoided already, maybe we can let
> > cpr-transfer depend on unix socket in -incoming, then integrate fd sharing
> > in the same channel?
> 
> You saw the answer in another thread, but I repeat it here for others benefit:
> 
>   "CPR state cannot be sent over the normal migration channel, because devices
>    and backends are created prior to reading the channel, so this mode sends
>    CPR state over a second migration channel that is not visible to the user.
>    New QEMU reads the second channel prior to creating devices or backends."

Today when looking again, I wonder about the other way round: can we make
the new parameter called "-incoming-cpr", working exactly the same as
"cpr-uri" qemu cmdline, but then after cpr is loaded it'll be automatically
be reused for migration incoming ports?

After all, cpr needs to happen already with unix sockets.  Having separate
cmdline options grants user to make the other one to be non-unix, but that
doesn't seem to buy us anything.. then it seems easier to always reuse it,
and restrict cpr-transfer to only work with unix sockets for incoming too?

-- 
Peter Xu