Re: [PATCH] KVM: x86: Always set kvm_run->if_flag

[Paolo Bonzini]

On 12/7/21 18:28, Marc Orr wrote:
> > > > > +static bool svm_get_if_flag(struct kvm_vcpu *vcpu)
> > > > > +{
> > > > > +     struct vmcb *vmcb = to_svm(vcpu)->vmcb;
> > > > > +
> > > > > +     return !!(vmcb->control.int_state & SVM_GUEST_INTERRUPT_MASK);
> > > > I'm not sure if this is always valid to use for non SEV-ES guests. Maybe
> > > > the better thing would be:
> > > >
> > > >           return sev_es_guest(vcpu->kvm) ? vmcb->control.int_state & SVM_GUEST_INTERRUPT_MASK
> > > >                                          : kvm_get_rflags(vcpu) & X86_EFLAGS_IF;
> > > >
> > > > (Since this function returns a bool, I don't think you need the !!)
> > >
> > > I had the same reservations when writing the patch. (Why fix what's
> > > not broken.) The reason I wrote the patch this way is based on what I
> > > read in APM vol2: Appendix B Layout of VMCB: "GUEST_INTERRUPT_MASK -
> > > Value of the RFLAGS.IF bit for the guest."
> >
> > I just verified with the hardware team that this flag is indeed only set
> > for a guest with protected state (SEV-ES / SEV-SNP). An update to the APM
> > will be made.
>
> Got it now. Then the change you suggested is a must! Thanks, Tom.

Besides, the bit wouldn't have existed on old (pre-SEV-ES) processors.

Paolo