KVM: x86: Use mutex guards to eliminate __kvm_x86_vendor_init()

Use the recently introduced guard(mutex) infrastructure acquire and
automatically release vendor_module_lock when the guard goes out of scope.
Drop the inner __kvm_x86_vendor_init(), its sole purpose was to simplify
releasing vendor_module_lock in error paths.

No functional change intended.
Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20231030141728.1406118-1-nik.borisov@suse.com
[sean: rewrite changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/kvm/x86.c

@@ -9632,11 +9632,13 @@ static void kvm_x86_check_cpu_compat(void *ret)
 	*(int *)ret = kvm_x86_check_processor_compatibility();
 }
 
-static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
+int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 {
 	u64 host_pat;
 	int r, cpu;
 
+	guard(mutex)(&vendor_module_lock);
+
 	if (kvm_x86_ops.hardware_enable) {
 		pr_err("already loaded vendor module '%s'\n", kvm_x86_ops.name);
 		return -EEXIST;
@@ -9766,17 +9768,6 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 	kmem_cache_destroy(x86_emulator_cache);
 	return r;
 }
-
-int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
-{
-	int r;
-
-	mutex_lock(&vendor_module_lock);
-	r = __kvm_x86_vendor_init(ops);
-	mutex_unlock(&vendor_module_lock);
-
-	return r;
-}
 EXPORT_SYMBOL_GPL(kvm_x86_vendor_init);
 
 void kvm_x86_vendor_exit(void)