Re: [PATCH v4 1/1] s390x: KVM: accept STSI for CPU topology information

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

On 9/16/21 4:03 PM, David Hildenbrand wrote:
> >   struct kvm_vm_stat {
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 51d1594bd6cd..f3887e13c5db 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -608,6 +608,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, 
> > long ext)
> >       case KVM_CAP_S390_PROTECTED:
> >           r = is_prot_virt_host();
> >           break;
> > +    case KVM_CAP_S390_CPU_TOPOLOGY:
> > +        r = test_facility(11);
> > +        break;
> >       default:
> >           r = 0;
> >       }
> > @@ -819,6 +822,19 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, 
> > struct kvm_enable_cap *cap)
> >           icpt_operexc_on_all_vcpus(kvm);
> >           r = 0;
> >           break;
> > +    case KVM_CAP_S390_CPU_TOPOLOGY:
>
> As given in my example, this should be
>
> r = -EINVAL;
> mutex_lock(&kvm->lock);
> if (kvm->created_vcpus) {
>      r = -EBUSY;
> } else if (test_facility(11)) {
> ...
> }
>
> Similar to how we handle KVM_CAP_S390_VECTOR_REGISTERS.
>
> [...]
>
> > +
> > +    /* PTF needs both host and guest facilities to enable 
> > interpretation */
> > +    if (test_kvm_facility(vcpu->kvm, 11) && test_facility(11))
> > +        vcpu->arch.sie_block->ecb |= ECB_PTF;
>
> This should be simplified to
>
> if (test_kvm_facility(vcpu->kvm, 11))
>
> then. (vsie code below is correct)

OK, the idea was to let the hypervisor the possibility to do userland 
emulation if it wanted.
But I can modify as you want.

Regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen