Re: [Qemu-devel] [PATCH 16/46] Add migration-capability boolean for postcopy-ram.

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Paolo Bonzini (pbonzini@redhat.com) wrote:
> Il 07/07/2014 22:23, Dr. David Alan Gilbert ha scritto:
> >I think what I need to do for that is:
> >   1) As for precopy add the option not to start the destination CPU on entry to postcopy;
> >      I think that's OK, because we can carry on in postcopy mode even if the destination
> >      CPU isn't running, we just won't generate page requests.
> >
> >Admittedly I don't quite understand how (1) is supposed to interact with device
> >state.
> 
> This is just passing "-S" on the destination side.  Device state is treated
> the same as without "-S" and can still generate page requests. The only
> difference is whether you have a vm_start() or not.

Good, that sounds easy enough.

> I think it should be possible to restart the VM on the source side after
> postcopy migration, as long as migration has failed or has been canceled.
> Whether that makes sense or causes dire disk corruption depends on the
> particular scenario, but then the same holds for precopy and we don't try at
> all to prevent "cont" at the end of migration.  It makes it much easier for
> libvirt to restart the source if it cannot continue on the destination.

Interesting; Andrea fell into accidentally starting his source and
was somewhat surprised.
I was just going to add the RAN_STATE_MEMORY_STALE that Lei Li added
in the exec-migration patchset.

Dave

> 
> Paolo
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK