Re: [PATCH v2 15/17] vfio/migration: Multifd device state transfer support - receive side

[Cédric Le Goater]

> > > > -    return vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
> > > > - vbasedev->migration->device_state, errp);
> > > > +    migration->load_bufs_thread_finished = false;
> > > > +    migration->load_bufs_thread_want_exit = false;
> > > > +    qemu_thread_create(&migration->load_bufs_thread, "vfio-load-bufs",
> > > > +                       vfio_load_bufs_thread, opaque, QEMU_THREAD_JOINABLE);
> > >
> > > The device state save threads are manged by migration core thread pool. Don't 
> > > we want to apply the same thread management scheme for the load flow as well?
> >
> > I think that (in contrast with the device state saving threads)
> > the buffer loading / reordering thread is an implementation detail
> > of the VFIO driver, so I don't think it really makes sense for multifd code
> > to manage it.

Is it an optimisation then ? In that case, could the implementation not
use threads ?

VFIO is complex, migration is complex, VFIO migration is even more. TBH,
the idea of doing thread management in the VFIO subsystem makes me feel
uncomfortable.

Thanks,

C.