Re: [PATCH v2 5/5] KVM: s390: vsie: Do the CRYCB validation first

Pierre Morel
2018-08-23T07:17:38Z

On 22/08/2018 19:15, David Hildenbrand wrote:
> On 22.08.2018 18:51, Pierre Morel wrote:
>> When entering the SIE the CRYCB validation better
>> be done independently of the instruction's
>> availability.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>> arch/s390/kvm/vsie.c | 11 ++++++-----
>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
>> index 7ee4329..fca25aa 100644
>> --- a/arch/s390/kvm/vsie.c
>> +++ b/arch/s390/kvm/vsie.c
>> @@ -164,17 +164,18 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>> /* format-1 is supported with message-security-assist extension 3 */
>> if (!test_kvm_facility(vcpu->kvm, 76))
>> return 0;
>> - /* we may only allow it if enabled for guest 2 */
>> - ecb3_flags = scb_o->ecb3 & vcpu->arch.sie_block->ecb3 &
>> - (ECB3_AES | ECB3_DEA);
>> - if (!ecb3_flags)
>> - return 0;
>>
>> if ((crycb_addr & PAGE_MASK) != ((crycb_addr + 128) & PAGE_MASK))
>> return set_validity_icpt(scb_s, 0x003CU);
>> if (!crycb_addr)
>> return set_validity_icpt(scb_s, 0x0039U);
>>
>> + /* we may only allow it if enabled for guest 2 */
>> + ecb3_flags = scb_o->ecb3 & vcpu->arch.sie_block->ecb3 &
>> + (ECB3_AES | ECB3_DEA);
>> + if (!ecb3_flags)
>> + return 0;
>> +
>> /* copy only the wrapping keys */
>> if (read_guest_real(vcpu, crycb_addr + 72,
>> vsie_page->crycb.dea_wrapping_key_mask, 56))
>>
>
> That makes sense, especially if ECB3_AES is used but effectively turned
> off by us.
>
> What is the expected behavior if ECB3_AES | ECB3_DEA are not set by g2
> for g3?
>

The use of functions PCKMO-Encrypt-DEA/AES induce a specification error.

However other MSA3 function will continue to be usable.

Regards,
Pierre

--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany