A previous commit changed the behaviour of the KVM_S390_VCPU_FAULT
ioctl. The current (wrong) implementation will trigger a guest
addressing exception if the requested address lies outside of a
memslot, unless the VM is UCONTROL.

Restore the previous behaviour by open coding the fault-in logic.

Fixes: 3762e905ec2e ("KVM: s390: use __kvm_faultin_pfn()")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index ebcb0ef8835e..aebc74974ddf 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5520,9 +5520,21 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 	}
 #endif
 	case KVM_S390_VCPU_FAULT: {
-		idx = srcu_read_lock(&vcpu->kvm->srcu);
-		r = vcpu_dat_fault_handler(vcpu, arg, 0);
-		srcu_read_unlock(&vcpu->kvm->srcu, idx);
+		gpa_t gaddr = arg;
+
+		scoped_guard(srcu, &vcpu->kvm->srcu) {
+			r = -EREMOTE;
+			if (vcpu_ucontrol_translate(vcpu, &gaddr))
+				break;
+
+			r = kvm_s390_faultin_gfn_simple(vcpu, NULL, gpa_to_gfn(gaddr), false);
+			if (r <= 0)
+				break;
+			if (r == PGM_ADDRESSING)
+				r = -ENOENT;
+			else
+				KVM_BUG_ON(r, vcpu->kvm);
+		}
 		break;
 	}
 	case KVM_ENABLE_CAP:
-- 
2.53.0