On Fri, Jun 17, 2016 at 04:25:57PM +0200, Paolo Bonzini wrote: > > > On 17/06/2016 15:41, Eduardo Habkost wrote: > > In theory, we should never initialize anything on the machine > > based on the host we are running. In practice we sometimes do > > that, and we know it's unsafe. Sending the value on the migration > > stream is a solution to detect when this breaks something. We did > > that before, for TSC frequency. > > > > I prefer to add a little extra code, than to waste time debugging > > when that stuff breaks. > > Fair enough (but still let's add and strip the 1s in pre_save and > post_load). It is a good justification for sending configuration over > the wire, that we initialize things based on the host we're running. > > But we shouldn't initialize more things based on the host (e.g. new > booleans should be "enforce"-style).
Strongly agreed. > Also I don't really like > introducing sanity checks for those that aren't based on the host (as in > the LMCE thread). This code will never trigger in practice, so it's > just extra cost for no benefit. Our experience with guest ABI and compatibility code tells me otherwise. Keeping guest ABI is hard, so I would always support adding extra code to help us catch mistakes (either in QEMU, management software, or user mistakes). -- Eduardo
