[PATCH 4.20 166/183] s390: vsie: Use effective CRYCBD.31 to check CRYCBD validity

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pierre Morel <pmorel@xxxxxxxxxxxxx>

commit b10bd9a256aec504c14a7c9b6fccb6301ecf290a upstream.

When facility.76 MSAX3 is present for the guest we must issue a validity
interception if the CRYCBD is not valid.

The bit CRYCBD.31 is an effective field and tested at each guest level
and has for effect to mask the facility.76

It follows that if CRYCBD.31 is clear and AP is not in use  we do not
have to test the CRYCBD validatity even if facility.76 is present in the
host.

Fixes: 6ee74098201b ("KVM: s390: vsie: allow CRYCB FORMAT-0")
Cc: stable@xxxxxxxxxxxxxxx

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
Reported-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Cornelia Huck <cohuck@xxxxxxxxxx>
Reviewed-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Message-Id: <1549876849-32680-1-git-send-email-pmorel@xxxxxxxxxxxxx>
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/s390/kvm/vsie.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/kvm/vsie.c
+++ b/arch/s390/kvm/vsie.c
@@ -297,7 +297,7 @@ static int shadow_crycb(struct kvm_vcpu
 	scb_s->crycbd = 0;
 
 	apie_h = vcpu->arch.sie_block->eca & ECA_APIE;
-	if (!apie_h && !key_msk)
+	if (!apie_h && (!key_msk || fmt_o == CRYCB_FORMAT0))
 		return 0;
 
 	if (!crycb_addr)