KVM: s390: implements the kvm_arch_vcpu_in_kernel()

This implements kvm_arch_vcpu_in_kernel() for s390.  DIAG is a privileged
operation, so it cannot be called from problem state (user mode).

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 5e07322..9f23a9e 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -2449,7 +2449,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
 
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu)
 {
-	return false;
+	return !(vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE);
 }
 
 void kvm_s390_vcpu_block(struct kvm_vcpu *vcpu)