Re: [PATCH 00/16] migration: Switchover phase refactoring

[Peter Xu]

On Wed, Jan 15, 2025 at 10:12:45AM +0100, Jiri Denemark wrote:
> On Tue, Jan 14, 2025 at 18:07:30 -0500, Peter Xu wrote:
> > CI: https://gitlab.com/peterx/qemu/-/pipelines/1625266692
> >     (note: warning is present on rust stuff, but shouldn't be relevant)
> > 
> > This series refactors the migration switchover path quite a bit.  I started
> > this work initially to measure the JSON writer overhead, but then I decided
> > to cleanup the switchover path in general when I am at it altogether, as I
> > wanted to do this for a long time.
> > 
> > A few major things I tried to do:
> > 
> ...
> >   - DEVICE migration state
> > 
> >     QEMU has a very special DEVICE migration state, that only happens with
> >     precopy, and only when pause-before-switchover capability is enabled.
> >     Due to that specialty we can't merge precopy and postcopy code on
> >     switchover starts, because the state machine will be different.
> > 
> >     However after I checked the history and also with libvirt developers,
> >     this seems unnecessary.  So I had one patch making DEVICE state to be
> >     the "switchover" phase for precopy/postcopy unconditionally.  That will
> >     make the state machine much easier for both modes, meanwhile nothing is
> >     expected to break with it (but please still shoot if anyone knows /
> >     suspect something will, or could, break..).
> 
> No problem from libvirt side...
> 
> Tested-by: Jiri Denemark <jdenemar@redhat.com>

This is definitely reassuring.. thanks a lot, Jiri!

-- 
Peter Xu