On Tue, 2021-03-16 at 09:16 +0100, Paolo Bonzini wrote:
> On 15/03/21 19:19, Maxim Levitsky wrote:
> > On Mon, 2021-03-15 at 18:56 +0100, Paolo Bonzini wrote:
> > > On 15/03/21 18:43, Maxim Levitsky wrote:
> > > > + if (!guest_cpuid_is_intel(vcpu)) {
> > > > + /*
> > > > + * If hardware supports Virtual VMLOAD VMSAVE then
> > > > enable it
> > > > + * in VMCB and clear intercepts to avoid #VMEXIT.
> > > > + */
> > > > + if (vls) {
> > > > + svm_clr_intercept(svm, INTERCEPT_VMLOAD);
> > > > + svm_clr_intercept(svm, INTERCEPT_VMSAVE);
> > > > + svm->vmcb->control.virt_ext |=
> > > > VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK;
> > > > + }
> > > > + /* No need to intercept these msrs either */
> > > > + set_msr_interception(vcpu, svm->msrpm,
> > > > MSR_IA32_SYSENTER_EIP, 1, 1);
> > > > + set_msr_interception(vcpu, svm->msrpm,
> > > > MSR_IA32_SYSENTER_ESP, 1, 1);
> > > > + }
> > >
> > > An "else" is needed here to do the opposite setup (removing the "if
> > > (vls)" from init_vmcb).
> >
> > init_vmcb currently set the INTERCEPT_VMLOAD and INTERCEPT_VMSAVE and it
> > doesn't enable vls
>
> There's also this towards the end of the function:
>
> /*
> * If hardware supports Virtual VMLOAD VMSAVE then enable it
> * in VMCB and clear intercepts to avoid #VMEXIT.
> */
> if (vls) {
> svm_clr_intercept(svm, INTERCEPT_VMLOAD);
> svm_clr_intercept(svm, INTERCEPT_VMSAVE);
> svm->vmcb->control.virt_ext |=
> VIRTUAL_VMLOAD_VMSAVE_ENABLE_MASK;
> }
>
> > thus there is nothing to do if I don't want to enable vls.
> > It seems reasonable to me.
> >
> > Both msrs I marked as '.always = false' in the
> > 'direct_access_msrs', which makes them be intercepted by the default.
> > If I were to use '.always = true' it would feel a bit wrong as the
> > intercept is not always
> > enabled.
>
> I agree that .always = false is correct.
>
> > What do you think?
>
> You can set the CPUID multiple times, so you could go from AMD to Intel
> and back.
I understand now, I will send V2 with that. Thanks for the review!
Best regards,
Maxim Levitsky
>
> Thanks,
>
> Paolo
>
