Re: [PATCH v2 2/5] KVM: s390: vsie: Only accept FORMAT1 CRYCB for guest2

David Hildenbrand
2018-08-22T16:55:46Z

On 22.08.2018 18:51, Pierre Morel wrote:
> As the comment above the function suggested the shadowing
> of the guest2 CRYCB can only accept a format 1 since
> AP instructions are not supported in the guest.
>
> Let's modify the check which allowed to accept a format 2 too.

As the bit is ignored without AP/APXA, it is perfectly valid to accept a
format 2, we just have to interpret it as format 1 (which is what we do)

What am I missing?

>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
> arch/s390/kvm/vsie.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
> index 12b9707..56a9d47 100644
> --- a/arch/s390/kvm/vsie.c
> +++ b/arch/s390/kvm/vsie.c
> @@ -156,7 +156,9 @@ static int shadow_crycb(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
> u8 ecb3_flags;
>
> scb_s->crycbd = 0;
> - if (!(crycbd_o & vcpu->arch.sie_block->crycbd & CRYCB_FORMAT1))
> + if (!(crycbd_o == CRYCB_FORMAT1))
> + return 0;

huh, this looks very broken. The address is still in there.

> + if (!(vcpu->arch.sie_block->crycbd & CRYCB_FORMAT1))
> return 0;
> /* format-1 is supported with message-security-assist extension 3 */
> if (!test_kvm_facility(vcpu->kvm, 76))
>

--

Thanks,

David / dhildenb