KVM: s390: ignore IBC if zero

Looks like we forgot about the special IBC value of 0 meaning "no IBC".
Let's fix that, otherwise it gets rounded up and suddenly an IBC is active
with the lowest possible machine.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Fixes: commit 053dd2308d81 ("KVM: s390: force ibc into valid range")
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 6d8ec3a..c9ae539 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -657,7 +657,7 @@ static int kvm_s390_set_processor(struct kvm *kvm, struct kvm_device_attr *attr)
                kvm->arch.model.cpuid = proc->cpuid;
                lowest_ibc = sclp.ibc >> 16 & 0xfff;
                unblocked_ibc = sclp.ibc & 0xfff;
-               if (lowest_ibc) {
+               if (lowest_ibc && proc->ibc) {
                        if (proc->ibc > unblocked_ibc)
                                kvm->arch.model.ibc = unblocked_ibc;
                        else if (proc->ibc < lowest_ibc)