Re: [RFC PATCH v3 46/59] KVM: VMX: Move register caching logic to common code

Paolo Bonzini
2021-11-29T22:48:49Z

On 11/29/21 19:23, Sean Christopherson wrote:
>>>> Only one generation of CPU, Nehalem, supports EPT but not
>>>> unrestricted guest, and disabling unrestricted guest without also
>>>> disabling EPT is, to put it bluntly, dumb.
>>> This one is only significantly better and lacks an explanation what this
>>> means for the dumb case.
>> Well, it means a retpoline (see paragraph before).
>
> No, the point being made is that, on a CPU that supports Unrestricted Guest (UG),
> disabling UG without disabling EPT is really, really stupid.

Yes, I understand that.

Thomas was asking what it means to "Move register caching logic to
common code", i.e. what the consequences are. The missing words at the
end of the first paragraph didn't make the connection obvious between
the extra retpoline and the "dumb case".

Paolo