Messages in this thread | | | Subject | Re: [PATCH v4 05/15] KVM: s390: enable/disable AP interpretive execution | From | Tony Krowiak <> | Date | Tue, 17 Apr 2018 14:11:11 -0400 |
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On 04/17/2018 12:55 PM, Pierre Morel wrote: > On 17/04/2018 18:22, Tony Krowiak wrote: >> On 04/17/2018 12:13 PM, Pierre Morel wrote: >>> On 17/04/2018 17:02, Tony Krowiak wrote: >>>> 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@linux.vnet.ibm.com> >>>>>> --- >>>>>> 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. >>> >>> really? why? >> >> The KVM_S390_VM_CPU_FEAT_AP will not be enabled by KVM if the AP >> instructions are not installed on the host. I assume - but have >> no way of verifying - that if the AP instructions are not installed >> on the host, that interpretation would fail. Do you know what would >> happen if AP instructions are interpreted when not installed on >> the host? > > If the host has no AP instructions (his ECA.28=0) but it set ECA.28 > for a guest, > there will be no AP instructions available in the guest.
Then there's the answer to your question; this is why we to test CPU_FEAT_AP.
> > >> >>> >>> >>>> >>>>> >>>>> >>>>> 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. >>> >>> Right same error I made all along this review. >>> But AFAIK it means AP instructions are provided to the guest. >>> Then should this function be called if the guest has no AP >>> instructions ? >>> >>> >>>> >>>>> >>>>>> + 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. >>> >>> Sorry, still the same error I made about CPU_FEAT_AP meaning AP >>> instructions in the guest >>> and not AP interpretation available. >>> Could apie be set if AP instruction are not supported? >>> >>>> >>>>> >>>>>> + vcpu->arch.sie_block->eca |= ECA_APIE; >>>>>> + >>>>>> + >>>>>> if (!test_kvm_facility(vcpu->kvm, 76)) >>>>>> return; >>>>>> >>>>> >>>> >>> >> >
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