I agree with your point that the common hypervisor practice to fake old model numbers will break some of the workarounds. Hypervisors may need to revisit their practice. > > In general, making these kinds of decisions based on F/M/S is probably > > unwise when running in a VM. > > Certainly. That's why I suggest not trusting f/m/s unless the > hypervisor is explicitly saying it's accurate. This would be only useful if there's an useful result of this non trust. But there isn't. Except for panic there's nothing you could do. And I don't think panic would be reasonable. The "Skylake bit " or "not skylake bit" doesn't make any sense to me. If a hypervisor wants to enable Skylake workarounds they need to provide the Skylake model number. If they don't think they need them because the VM can never be migrated to Skylake, then they don't need to set that model number. So there isn't any need for inventing any new bits, it's all already possible. -Andi
