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

[Pierre Morel]

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@xxxxxxxxxxxxx>
> > ---
> >   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 BÃblingen - Germany