linux-kernel - Re: [PATCH v9 07/22] KVM: s390: refactor crypto initialization

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Date:   Tue, 21 Aug 2018 09:29:08 -0400
From:   Tony Krowiak <akrowiak@...ux.ibm.com>
To:     David Hildenbrand <david@...hat.com>,
        Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, pmorel@...ux.vnet.ibm.com,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        jjherne@...ux.vnet.ibm.com, thuth@...hat.com,
        pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com
Subject: Re: [PATCH v9 07/22] KVM: s390: refactor crypto initialization

On 08/20/2018 04:41 PM, David Hildenbrand wrote:
>>>> +	if (test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))
>>>> +		vcpu->arch.sie_block->eca |= ECA_APIE;
>>>>    
>>>> -	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>>>> +	/* If MSAX3 is installed on the guest, set up protected key support */
>>>> +	if (test_kvm_facility(vcpu->kvm, 76)) {
>>>> +		if (vcpu->kvm->arch.crypto.aes_kw)
>>>> +			vcpu->arch.sie_block->ecb3 |= ECB3_AES;
>>>> +		if (vcpu->kvm->arch.crypto.dea_kw)
>>>> +			vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
>>>> +	}
>>> As the feature can never change, and aes_kw/dea_kw are only set to 1 in
>>> case we have test_kvm_facility(vcpu->kvm, 76), this change is not needed.
>>>
>>> I think this function can be pretty much left alone. Just add the
>>> KVM_S390_VM_CPU_FEAT_AP handling.
>> I disagree, what about the case where the KVM_S390_VM_CPU_FEAT_AP is
>> configured for the guest but the MSAX3 facility (76) is not?
> Then aes_kw/dea_kw can never be set.
>
> kvm_s390_vm_set_crypto() and kvm_s390_crypto_init() correctly test for
> facility 76.
>
> Or am I missing a case?

I stand corrected, you are right. I'll remove the test.

>
>>>>    }
>>>>    
>>>>    void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
>>>>
>