On Fri, Jun 30, 2023, Gil Neiger wrote: > Intel will not produce any CPU with CET that does not enumerate IA32_VMX_BASIC[56] as 1. > > One can check that bit before injecting a #CP with error code, but it should > not be necessary if CET is enumerated. > > Of course, if the KVM may run as a guest of another VMM/hypervisor, it may be > that the virtual CPU in which KVM operates may enumerate CET but clear the > bit in IA32_VMX_BASIC. Yeah, I think KVM should be paranoid and expose CET to the guest if and only if IA32_VMX_BASIC[56] is 1. That'll also help validate nested support, e.g. will make it more obvious if userspace+KVM provides a "bad" model to L1.
