Re: [PATCH v4 05/15] KVM: s390: enable/disable AP interpretive execution

[Tony Krowiak]

On 04/16/2018 06:51 AM, Pierre Morel wrote:
> On 15/04/2018 23:22, Tony Krowiak wrote:
> > The VFIO AP device model exploits interpretive execution of AP
> > instructions (APIE) to provide guests passthrough access to AP
> > devices. This patch introduces a new interface to enable and
> > disable APIE.
> >
> > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
> > ---
> >   arch/s390/include/asm/kvm-ap.h   |   16 ++++++++++++++++
> >   arch/s390/include/asm/kvm_host.h |    1 +
> >   arch/s390/kvm/kvm-ap.c           |   20 ++++++++++++++++++++
> >   arch/s390/kvm/kvm-s390.c         |    9 +++++++++
> >   4 files changed, 46 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/s390/include/asm/kvm-ap.h 
> > b/arch/s390/include/asm/kvm-ap.h
> > index 736e93e..a6c092e 100644
> > --- a/arch/s390/include/asm/kvm-ap.h
> > +++ b/arch/s390/include/asm/kvm-ap.h
> > @@ -35,4 +35,20 @@
> >    */
> >   void kvm_ap_build_crycbd(struct kvm *kvm);
> >
> > +/**
> > + * kvm_ap_interpret_instructions
> > + *
> > + * Indicate whether AP instructions shall be interpreted. If they 
> > are not
> > + * interpreted, all AP instructions will be intercepted and routed 
> > back to
> > + * userspace.
> > + *
> > + * @kvm: the virtual machine attributes
> > + * @enable: indicates whether AP instructions are to be interpreted 
> > (true) or
> > + *        or not (false).
> > + *
> > + * Returns 0 if completed successfully; otherwise, returns -EOPNOTSUPP
> > + * indicating that AP instructions are not installed on the guest.
> > + */
> > +int kvm_ap_interpret_instructions(struct kvm *kvm, bool enable);
> > +
> >   #endif /* _ASM_KVM_AP */
> > diff --git a/arch/s390/include/asm/kvm_host.h 
> > b/arch/s390/include/asm/kvm_host.h
> > index 3162783..5470685 100644
> > --- a/arch/s390/include/asm/kvm_host.h
> > +++ b/arch/s390/include/asm/kvm_host.h
> > @@ -715,6 +715,7 @@ struct kvm_s390_crypto {
> >       __u32 crycbd;
> >       __u8 aes_kw;
> >       __u8 dea_kw;
> > +    __u8 apie;
> >   };
> >
> >   #define APCB0_MASK_SIZE 1
> > diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> > index 991bae4..55d11b5 100644
> > --- a/arch/s390/kvm/kvm-ap.c
> > +++ b/arch/s390/kvm/kvm-ap.c
> > @@ -58,3 +58,23 @@ void kvm_ap_build_crycbd(struct kvm *kvm)
> >       }
> >   }
> >   EXPORT_SYMBOL(kvm_ap_build_crycbd);
> > +
> > +int kvm_ap_interpret_instructions(struct kvm *kvm, bool enable)
> > +{
> > +    int ret = 0;
> > +
> > +    mutex_lock(&kvm->lock);
> > +
> > +    if (!test_kvm_cpu_feat(kvm, KVM_S390_VM_CPU_FEAT_AP)) {
>
> Do we really need to test CPU_FEAT_AP?

Yes we do.

> I understand that KVM_S390_VM_CPU_FEAT_AP means AP instructions are 
> interpreted.
> shouldn't we add this information in the name?
> like KVM_S390_VM_CPU_FEAT_APIE

KVM_S390_VM_CPU_FEAT_AP does NOT mean AP instructions are interpreted, 
it means
AP instructions are installed.

> > +        ret = -EOPNOTSUPP;
> > +        goto done;
> > +    }
> > +
> > +    kvm->arch.crypto.apie = enable;
> > +    kvm_s390_vcpu_crypto_reset_all(kvm);
> > +
> > +done:
> > +    mutex_unlock(&kvm->lock);
> > +    return ret;
> > +}
> > +EXPORT_SYMBOL(kvm_ap_interpret_instructions);
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index 55cd897..1dc8566 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -1901,6 +1901,9 @@ static void kvm_s390_crypto_init(struct kvm *kvm)
> >       kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
> >       kvm_ap_build_crycbd(kvm);
> >
> > +    /* Default setting indicating SIE shall interpret AP 
> > instructions */
> > +    kvm->arch.crypto.apie = 1;
> > +
> >       if (!test_kvm_facility(kvm, 76))
> >           return;
> >
> > @@ -2434,6 +2437,12 @@ static void kvm_s390_vcpu_crypto_setup(struct 
> > kvm_vcpu *vcpu)
> >   {
> >       vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
> >
> > +    vcpu->arch.sie_block->eca &= ~ECA_APIE;
> > +    if (vcpu->kvm->arch.crypto.apie &&
> > +        test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))
>
> Do we call xxx_crypto_setup() if KVM does not support AP interpretation?

Yes, kvm_s390_vcpu_crypto_setup(vcpu) is called by kvm_arch_vcpu_setup(vcpu)
as well as from kvm_s390_vcpu_crypto_reset_all(kvm). Calling it has nothing
to do with whether AP interpretation is supported or not as it does much
more than that, including setting up of wrapping keys and the CRYCBD.

> > +        vcpu->arch.sie_block->eca |= ECA_APIE;
> > +
> > +
> >       if (!test_kvm_facility(vcpu->kvm, 76))
> >           return;