Re: [Qemu-devel] fw cfg files cross-version migration races

[Michael S. Tsirkin]

On Mon, Jun 08, 2015 at 09:21:45AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > > So, sorting entries (and the index assigned too) should fix this, right?
> > > That looks easiest to me.
> > 
> > Presumably, anything happening before (and after) user-provided blobs
> > are inserted will continue happening in the same order everywhere.
> 
> Which might change in the future though, in case the initialization
> order changes for some reason.  It's not a problem we have at the
> moment, so this stuff isn't urgent.  But we might face it in the future.
> 
> > So we really only have to sort the user provided blobs, so that if
> > the same *set* is provided on both ends of the migration, things would
> > work out OK.
> 
> I would simply sort everything (and do it for new machine types only,
> for backward compatibility reasons).  Sorting user-provided blobs only
> adds complexity for no reason.
> 
> > If a *different* set of blobs is specified on the migration origin vs.
> > the migration destination, we lose by default and worrying about it is
> > pointless -- did I get that right ?
> 
> Yes.  For migration to succeed you have to supply the same configuration
> on both ends.  That includes user-provided fw_cfg blobs of course.
> 
> cheers,
>   Gerd
> 

Do we want this for all machine types, or only for new ones?

-- 
MST