[PATCH 4/6] KVM: PPC: Book3E: Add AltiVec support

[Caraman Mihai Claudiu-B02008]

> >>> +
> >>> 	if (!vcpu->arch.sane) {
> >>> 		kvm_run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> >>> 		return -EINVAL;
> >>> @@ -716,6 +750,22 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run,
> >> struct kvm_vcpu *vcpu)
> >>> 	kvmppc_load_guest_fp(vcpu);
> >>> #endif
> >>>
> >>> +#ifdef CONFIG_ALTIVEC
> >>
> >> /* Switch from user space Altivec to guest Altivec state */
> >>
> >>> +	if (cpu_has_feature(CPU_FTR_ALTIVEC)) {
> >>
> >> Why not use your kvmppc_supports_altivec() helper here?
> >
> > Give it a try ... because Linus guarded this members with
> CONFIG_ALTIVEC :)
> 
> Huh? You already are in an #ifdef CONFIG_ALTIVEC here. I think it's a
> good idea to be consistent in helper usage. And the name you gave to the
> helper (kvmppc_supports_altivec) is actually quite nice and tells us
> exactly what we're asking for.

I thought you asking to replace #ifdef CONFIG_ALTIVEC.

> >> Do we need to do this even when the guest doesn't use Altivec? Can't
> we
> >> just load it on demand then once we fault? This code path really
> should
> >> only be a prefetch enable when MSR_VEC is already set in guest
> context.
> >
> > No we can't, read 6/6.
> 
> So we have to make sure we're completely unlazy when it comes to a KVM
> guest. Are we?

Yes, because MSR[SPV] is under its control.

-Mike