Re: [PATCH v8 07/22] KVM: s390: refactor crypto initialization

Tony Krowiak
2018-08-10T16:13:17Z

On 08/09/2018 01:58 AM, Janosch Frank wrote:
> On 08.08.2018 16:44, Tony Krowiak wrote:
>> From: Tony Krowiak <akrowiak@linux.ibm.com>
>>
>> This patch refactors the code that initializes and sets up the
>> crypto configuration for a guest. The following changes are
>> implemented via this patch:
>>
>> 1. Prior to the introduction of AP device virtualization, it
>> was not necessary to provide guest access to the CRYCB
>> unless the MSA extension 3 (MSAX3) facility was installed
>> on the host system. With the introduction of AP device
>> virtualization, the CRYCB must be made accessible to the
>> guest if the AP instructions are installed on the host
>> and are to be provided to the guest.
>>
>> 2. Introduces a flag indicating AP instructions executed on
>> the guest shall be interpreted by the firmware. It is
>> initialized to indicate AP instructions are to be
>> to be interpreted and is used to set the SIE bit for
>> each vcpu during vcpu setup.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
>> Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
>> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> Tested-by: Michael Mueller <mimu@linux.ibm.com>
>> Tested-by: Farhan Ali <alifm@linux.ibm.com>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Acked-by: Janosch Frank <frankja@linux.ibm.com>
>
>> ---
>> arch/s390/include/asm/kvm_host.h | 3 +
>> arch/s390/include/uapi/asm/kvm.h | 1 +
>> arch/s390/kvm/kvm-s390.c | 86 ++++++++++++++++++++------------------
>> 3 files changed, 49 insertions(+), 41 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
>> index af39561..0c13f61 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -187,6 +187,7 @@ struct kvm_s390_sie_block {
>> #define ECA_AIV 0x00200000
>> #define ECA_VX 0x00020000
>> #define ECA_PROTEXCI 0x00002000
>> +#define ECA_APIE 0x00000008
>> #define ECA_SII 0x00000001
>> __u32 eca; /* 0x004c */
>> #define ICPT_INST 0x04
>> @@ -256,6 +257,7 @@ struct kvm_s390_sie_block {
>> __u8 reservede4[4]; /* 0x00e4 */
>> __u64 tecmc; /* 0x00e8 */
>> __u8 reservedf0[12]; /* 0x00f0 */
>> +#define CRYCB_FORMAT_MASK 0x00000003
>> #define CRYCB_FORMAT1 0x00000001
>> #define CRYCB_FORMAT2 0x00000003
>> __u32 crycbd; /* 0x00fc */
>> @@ -714,6 +716,7 @@ struct kvm_s390_crypto {
>> __u32 crycbd;
>> __u8 aes_kw;
>> __u8 dea_kw;
>> + __u8 apie;
> In the last review I wanted a comment here to know what they do.

I'm not sure what the 'they' are that you reference here. I couldn't
find your review comment but I assume you are looking for a comment
explaining what the 'apie' field is used for. I am removing
the 'apie' field based on a review comment by David, so there is
no longer a need for a comment here, assuming that is what you
are referring to.

>
>> static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
>> {
>> - if (!test_kvm_facility(vcpu->kvm, 76))
>> + /*
>> + * If neither the AP instructions nor the MSAX3 facility are installed
>> + * on the host, then there is no need for a CRYCB in SIE because the
>> + * they will not be installed on the guest either.
> the they

I'll fix this grammatical error.

>
>> + */
>> + if (ap_instructions_available() && !test_facility(76))
>> return;
> I know you're not responsible for that one :) but 0 being the wanted
> value here is a bit counter-intuitive.

Based on another review comment by David, I've changed this to:

if (!test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP) &&
!test_kvm_facility(vcpu->kvm, 76))

>
>>
>> - vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
>> + vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>> +
>> + vcpu->arch.sie_block->eca &= ~ECA_APIE;
> The scb is zero allocated, are the ECA and the ECB3s set somewhere
> in-between, or is that your way of making sure the controls are
> definitely gone for good?

It is a bit of defensive programming. There is a KVM_SET_DEVICE_ATTR
ioctl to set crypto attributes (KVM_S390_VM_CRYPTO) that ultimately
calls the kvm_s390_vm_set_crypto() function. You'll notice that at the
end of that function, there is a call to kvm_s390_vcpu_crypto_reset_all()
that calls the kvm_s390_vcpu_crypto_setup() for each vcpu, so it would
seem that there is the possiblility that there could be a need to
set ECB3 to a different value. At any rate, I see no good reason to
remove this.

>
>> + if (vcpu->kvm->arch.crypto.apie &&
>> + test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))
>> + vcpu->arch.sie_block->eca |= ECA_APIE;
>>
>> - 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;
>> + /* If MSAX3 is installed on the guest, set up protected key support */
>> + if (test_kvm_facility(vcpu->kvm, 76)) {
>> + vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
>>
>> - vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
>> + 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;
>> + }
>> }
>>
>> void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)
>>
>