KVM: PPC: Decrement module refcount if init_vm fails

We increment the reference count for KVM-HV/PR before the call to
kvmppc_core_init_vm. If that function fails we need to decrement the
refcount.

Also remove the check on kvm_ops->owner because try_module_get can
handle a NULL module.

Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220125155735.1018683-5-farosas@linux.ibm.com

Author: farosas

arch/powerpc/kvm/powerpc.c

@@ -453,6 +453,8 @@ int kvm_arch_check_processor_compat(void *opaque)
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 {
 	struct kvmppc_ops *kvm_ops = NULL;
+	int r;
+
 	/*
 	 * if we have both HV and PR enabled, default is HV
 	 */
@@ -474,11 +476,14 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
 	} else
 		goto err_out;
 
-	if (kvm_ops->owner && !try_module_get(kvm_ops->owner))
+	if (!try_module_get(kvm_ops->owner))
 		return -ENOENT;
 
 	kvm->arch.kvm_ops = kvm_ops;
-	return kvmppc_core_init_vm(kvm);
+	r = kvmppc_core_init_vm(kvm);
+	if (r)
+		module_put(kvm_ops->owner);
+	return r;
 err_out:
 	return -EINVAL;
 }