Re: [PATCH v5 02/13] KVM: s390: refactor crypto initialization

[Tony Krowiak <akrowiak@linux.vnet.ibm.com>]

On 05/16/2018 04:51 AM, Pierre Morel wrote:
> On 07/05/2018 17:11, Tony Krowiak wrote:
>> This patch refactors the code that initializes the crypto
>> configuration for a guest. The crypto configuration is contained in
>> a crypto control block (CRYCB) which is a satellite control block to
>> our main hardware virtualization control block. The CRYCB is
>> attached to the main virtualization control block via a CRYCB
>> designation (CRYCBD) designation field containing the address of
>> the CRYCB as well as its format.
>>
>> Prior to the introduction of AP device virtualization, there was
>> no need to provide access to or specify the format of the CRYCB for
>> a guest unless the MSA extension 3 (MSAX3) facility was installed
>> on the host system. With the introduction of AP device virtualization,
>> the CRYCB and its format must be made accessible to the guest
>> regardless of the presence of the MSAX3 facility as long as the
>> AP instructions are installed on the host.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>
>> ---
>>   arch/s390/include/asm/kvm_host.h |    1 +
>>   arch/s390/kvm/kvm-s390.c         |   64 
>> ++++++++++++++++++++++++++-----------
>>   2 files changed, 46 insertions(+), 19 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h 
>> b/arch/s390/include/asm/kvm_host.h
>> index 81cdb6b..5393c4d 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -255,6 +255,7 @@ 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 */
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 1f50de7..99779a6 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -1875,14 +1875,35 @@ long kvm_arch_vm_ioctl(struct file *filp,
>>       return r;
>>   }
>>
>> -static void kvm_s390_set_crycb_format(struct kvm *kvm)
>> +/*
>> + * The format of the crypto control block (CRYCB) is specified in 
>> the 3 low
>> + * order bits of the CRYCB designation (CRYCBD) field as follows:
>> + * Format 0: Neither the message security assist extension 3 (MSAX3) 
>> nor the
>> + *             AP extended addressing (APXA) facility are installed.
>> + * Format 1: The APXA facility is not installed but the MSAX3 
>> facility is.
>> + * Format 2: Both the APXA and MSAX3 facilities are installed
>> + */
>> +static void kvm_s390_format_crycb(struct kvm *kvm)
>>   {
>> -    kvm->arch.crypto.crycbd = (__u32)(unsigned long) 
>> kvm->arch.crypto.crycb;
>> +    /* Clear the CRYCB format bits - i.e., set format 0 by default */
>> +    kvm->arch.crypto.crycbd &= ~(CRYCB_FORMAT_MASK);
>> +
>> +    /* Check whether MSAX3 is installed */
>> +    if (!test_kvm_facility(kvm, 76))
>> +        return;
>>
>>       if (kvm_ap_apxa_installed())
>>           kvm->arch.crypto.crycbd |= CRYCB_FORMAT2;
>>       else
>>           kvm->arch.crypto.crycbd |= CRYCB_FORMAT1;
>> +
>> +    /* Enable AES/DEA protected key functions by default */
>> +    kvm->arch.crypto.aes_kw = 1;
>> +    kvm->arch.crypto.dea_kw = 1;
>> + get_random_bytes(kvm->arch.crypto.crycb->aes_wrapping_key_mask,
>> + sizeof(kvm->arch.crypto.crycb->aes_wrapping_key_mask));
>> + get_random_bytes(kvm->arch.crypto.crycb->dea_wrapping_key_mask,
>> + sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
>>   }
>>
>>   static u64 kvm_s390_get_initial_cpuid(void)
>> @@ -1896,19 +1917,17 @@ static u64 kvm_s390_get_initial_cpuid(void)
>>
>>   static void kvm_s390_crypto_init(struct kvm *kvm)
>>   {
>> -    if (!test_kvm_facility(kvm, 76))
>> +    /*
>> +     * If neither the AP instructions nor the message security assist
>> +     * extension 3 (MSAX3) are installed, there is no need to 
>> initialize a
>> +     * crypto control block (CRYCB) for the guest.
>> +     */
>> +    if (!kvm_ap_instructions_available() && !test_kvm_facility(kvm, 
>> 76))
>>           return;
>>
>>       kvm->arch.crypto.crycb = &kvm->arch.sie_page2->crycb;
>> -    kvm_s390_set_crycb_format(kvm);
>
>
> For my point of view the all patch can be reduced to putting this
> call (kvm_s390_set_crycb_format(kvm);) before testing for facility 76.
>
> (and setting the format correctly in kvm_s390_set_crycb_format(kvm))

I don't see what that buys us; it will just be reshuffling of the logic.
The idea here is that all of the code related to formatting the CRYCB for
use by the guest is contained in the kvm_s390_format_crycb(kvm) function.
We don't need a CRYCB, however, if the AP instructions are not installed
and the MSAX3 facility is not installed, so why even call
kvm_s390_format_crycb(kvm) in that case?

>
>
>
>> -
>> -    /* Enable AES/DEA protected key functions by default */
>> -    kvm->arch.crypto.aes_kw = 1;
>> -    kvm->arch.crypto.dea_kw = 1;
>> - get_random_bytes(kvm->arch.crypto.crycb->aes_wrapping_key_mask,
>> - sizeof(kvm->arch.crypto.crycb->aes_wrapping_key_mask));
>> - get_random_bytes(kvm->arch.crypto.crycb->dea_wrapping_key_mask,
>> - sizeof(kvm->arch.crypto.crycb->dea_wrapping_key_mask));
>> +    kvm->arch.crypto.crycbd = (__u32)(unsigned long) 
>> kvm->arch.crypto.crycb;
>> +    kvm_s390_format_crycb(kvm);
>>   }
>>
>>   static void sca_dispose(struct kvm *kvm)
>> @@ -2430,17 +2449,24 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu 
>> *vcpu)
>>
>>   static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
>>   {
>> -    if (!test_kvm_facility(vcpu->kvm, 76))
>> +    /*
>> +     * If a crypto control block designation (CRYCBD) has not been
>> +     * initialized
>> +     */
>> +    if (vcpu->kvm->arch.crypto.crycbd == 0)
>>           return;
>>
>> -    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;
>> +    /* If MSAX3 is installed, 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)
>
>