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

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Date:   Thu, 23 Aug 2018 09:31:32 +0200
From:   David Hildenbrand <david@...hat.com>
To:     pmorel@...ux.ibm.com
Cc:     linux-kernel@...r.kernel.org, cohuck@...hat.com,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        frankja@...ux.ibm.com, akrowiak@...ux.ibm.com,
        borntraeger@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com
Subject: Re: [PATCH v2 5/5] KVM: s390: vsie: Do the CRYCB validation first

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@...ux.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