Re: [PATCH v2 1/3] KVM: x86: add support for user wait instructions

[Paolo Bonzini]

On 27/05/19 12:30, Peter Zijlstra wrote:
>> This patch adds support for UMONITOR, UMWAIT and TPAUSE instructions
>> in kvm, and by default dont't expose it to kvm and provide a capability
>> to enable it.
>
> I'm thinking this should be conditional on the guest being a 1:1 guest,
> and I also seem to remember we have bits for that already -- they were
> used to disable paravirt spinlocks for example.

This should be userspace's choice.  It would indeed be silly to enable
this while overcommitted, but KVM doesn't really care.

Paolo