RE: [PATCH 2/2] x86/speculation: Support "Enhanced IBRS" on future CPUs

[Van De Ven, Arjan]

> >> For bonus points:  What should happen to a VM that is live migrated
> >> from one hypervisor to another, and the hypervisors have different
> >> IBRS support?
> >
> > Doctor Doctor it hurts when I do this....
> >
> > Migration tends to only work between HV's that are relatively
> > homogeneous, that's nothing new...
> 
> No Arjan, this is just wrong.  Well, I suppose it's right in the present
> tense with the IBRS mess on Skylake, but it's _not_ been true until last
> year.


I meant software wise. You're not going to live migrate from xen to kvm or backwards. or between very radically different versions of the kvm stack.