Messages in this thread | | | Subject | Re: [PATCH v4 05/15] KVM: s390: enable/disable AP interpretive execution | From | Pierre Morel <> | Date | Tue, 17 Apr 2018 18:55:08 +0200 |
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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.
> >> >> >>> >>>> >>>> >>>> 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; >>>>> >>>> >>> >> >
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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