KVM: s390: Do s390 specific init without bouncing through kvm_init()

Move the guts of kvm_arch_init() into a new helper, __kvm_s390_init(),
and invoke the new helper directly from kvm_s390_init() instead of
bouncing through kvm_init().  Invoking kvm_arch_init() is the very
first action performed by kvm_init(), i.e. this is a glorified nop.

Moving setup to __kvm_s390_init() will allow tagging more functions as
__init, and emptying kvm_arch_init() will allow dropping the hook
entirely once all architecture implementations are nops.

No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20221130230934.1014142-28-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/s390/kvm/kvm-s390.c

@@ -469,7 +469,7 @@ static void kvm_s390_cpu_feat_init(void)
 	 */
 }
 
-int kvm_arch_init(void *opaque)
+static int __kvm_s390_init(void)
 {
 	int rc = -ENOMEM;
 
@@ -527,7 +527,7 @@ int kvm_arch_init(void *opaque)
 	return rc;
 }
 
-void kvm_arch_exit(void)
+static void __kvm_s390_exit(void)
 {
 	gmap_unregister_pte_notifier(&gmap_notifier);
 	gmap_unregister_pte_notifier(&vsie_gmap_notifier);
@@ -541,6 +541,16 @@ void kvm_arch_exit(void)
 	debug_unregister(kvm_s390_dbf_uv);
 }
 
+int kvm_arch_init(void *opaque)
+{
+	return 0;
+}
+
+void kvm_arch_exit(void)
+{
+
+}
+
 /* Section: device related */
 long kvm_arch_dev_ioctl(struct file *filp,
 			unsigned int ioctl, unsigned long arg)
@@ -5696,7 +5706,7 @@ static inline unsigned long nonhyp_mask(int i)
 
 static int __init kvm_s390_init(void)
 {
-	int i;
+	int i, r;
 
 	if (!sclp.has_sief2) {
 		pr_info("SIE is not available\n");
@@ -5712,12 +5722,23 @@ static int __init kvm_s390_init(void)
 		kvm_s390_fac_base[i] |=
 			stfle_fac_list[i] & nonhyp_mask(i);
 
-	return kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
+	r = __kvm_s390_init();
+	if (r)
+		return r;
+
+	r = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
+	if (r) {
+		__kvm_s390_exit();
+		return r;
+	}
+	return 0;
 }
 
 static void __exit kvm_s390_exit(void)
 {
 	kvm_exit();
+
+	__kvm_s390_exit();
 }
 
 module_init(kvm_s390_init);