Re: [qemu-s390x] [PATCH v3 4/7] s390x/kvm: interface to interpret AP instructions

[Tony Krowiak]

On 03/26/2018 04:38 AM, David Hildenbrand wrote:
> On 16.03.2018 00:24, Tony Krowiak wrote:
> > The VFIO AP device exploits interpretive execution of AP
> > instructions (APIE). APIE is enabled by setting a device attribute
> > via the KVM_SET_DEVICE_ATTR ioctl.
> >
> > Signed-off-by: Tony Krowiak <address@hidden>
> > ---
> >   target/s390x/kvm.c       |   16 ++++++++++++++++
> >   target/s390x/kvm_s390x.h |    2 ++
> >   2 files changed, 18 insertions(+), 0 deletions(-)
> >
> > diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> > index 33e5ec3..2812e28 100644
> > --- a/target/s390x/kvm.c
> > +++ b/target/s390x/kvm.c
> > @@ -277,6 +277,22 @@ static void kvm_s390_init_dea_kw(void)
> >       }
> >   }
> >   
> > +int kvm_s390_set_interpret_ap(uint8_t enable)
> > +{
> > +    struct kvm_device_attr attribute = {
> > +        .group = KVM_S390_VM_CRYPTO,
> > +        .attr  = KVM_S390_VM_CRYPTO_INTERPRET_AP,
> > +        .addr = 1,
> > +    };
> > +
> > +    if (!kvm_vm_check_attr(kvm_state, KVM_S390_VM_CRYPTO,
> > +                           KVM_S390_VM_CRYPTO_INTERPRET_AP)) {
> > +        return -EOPNOTSUPP;
> > +    }
> > +
> > +    return kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attribute);
> > +}
> > +
> >   void kvm_s390_crypto_reset(void)
> >   {
> >       if (s390_has_feat(S390_FEAT_MSA_EXT_3)) {
> > diff --git a/target/s390x/kvm_s390x.h b/target/s390x/kvm_s390x.h
> > index 34ee7e7..0d6c6e7 100644
> > --- a/target/s390x/kvm_s390x.h
> > +++ b/target/s390x/kvm_s390x.h
> > @@ -40,4 +40,6 @@ void kvm_s390_crypto_reset(void);
> >   void kvm_s390_restart_interrupt(S390CPU *cpu);
> >   void kvm_s390_stop_interrupt(S390CPU *cpu);
> >   
> > +int kvm_s390_set_interpret_ap(uint8_t enable);
> > +
> >   #endif /* KVM_S390X_H */
> Wonder if a capability - like we use e.g. for SIGP user space
> interpretation - would be a better fit.
>
> We can provide the AP feature to the guest in case:
> - KVM_S390_VM_CPU_FEAT_AP ("interpretation support") is available
> - KVM_S390_VM_CRYPTO_INTERPRET_AP ("interception support") is available
I don't think we need this. I have found a way to set ECA_APIE from the
vfio_ap device driver, so there is no need to do it from the guest. Stay
tuned to this station for v4 of the patch series.
> I am missing the second check in your code. (for now you only rely on
> KVM_S390_VM_CPU_FEAT_AP)
For what else are you suggesting we need to check?
> I think you have to change the order of the patches so they work also
> properly when bisectin.
I'll take a look at it.
>