On Tue, 2010-10-05 at 14:58 -0600, Alex Williamson wrote: > On Tue, 2010-10-05 at 15:49 -0500, Anthony Liguori wrote: > > On 10/05/2010 03:46 PM, Alex Williamson wrote: > > > On Tue, 2010-10-05 at 15:41 -0500, Anthony Liguori wrote: > > > > > >> On 10/05/2010 03:35 PM, Alex Williamson wrote: > > >> > > >>> I was thinking of making KVM VMs with assigned PCI devices > > >>> unsavable/unmigratable, but I wasn't thrilled with the > > >>> no_migrate solutions. The more generic solutions seems to be > > >>> simply letting save handlers return an error if the device can't > > >>> be migrated. This is also much more generic than a one-way > > >>> bit flip of the no_migrate flag. For a vmsd based registration, > > >>> the pre_save() routine seems to be the right place to allow > > >>> devices to abort. The series also carries the error back through > > >>> all the vmstate callers. If this looks good, I'll give it some > > >>> more testing and submit as non-RFC. Thanks, > > >>> > > >>> > > >> Doesn't this mean that we don't fail the migration until after > > >> transferring all of the memory contents? > > >> > > > That's the case with the current no_migrate implementation too, it > > > doesn't get called until qemu_savevm_state_complete(). Thanks, > > > > > > > Ouch, that's unfortunate but also should be easily fixable. > > > > But making a save handler fail seems would make it impossible to get > > instant failure semantics. > > True. Ok, so maybe we do still need a separate no migrate registration. > In any case, I think it's a good idea to allow the save routines to have > a failure path, but I'll work on a way to disable migration that's not > quite so coupled with the savevm entry (it seems silly for device > assignment to register a savevm only for the purpose of then registering > as non-migratable). Thanks,
On second thought, I think we should take the same approach with the live handlers. We just need to make SaveSetParamsHandler return an int and check it and the SaveLiveStateHandler return for < 0. Then we have a full spectrum of points at which a savevm handler can abort a migration. If that sounds reasonable, I'll send a new series tomorrow. Thanks, Alex
