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

David Hildenbrand
2018-08-23T07:31:32Z

On 23.08.2018 09:17, Pierre Morel wrote:
> 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.

No, I meant which checks should be performed here.

>
> Regards,
> Pierre
>

--

Thanks,

David / dhildenb