KVM: MMU: fix missing percpu counter destroy

commit ad05c88266b4cce1c820928ce8a0fb7690912ba1
(KVM: create aggregate kvm_total_used_mmu_pages value)
introduce percpu counter kvm_total_used_mmu_pages but never
destroy it, this may cause oops when rmmod & modprobe.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Acked-by: Tim Pepper <lnxninja@linux.vnet.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/mmu.c

@@ -3185,6 +3185,7 @@ static void mmu_destroy_caches(void)
 void kvm_mmu_module_exit(void)
 {
 	mmu_destroy_caches();
+	percpu_counter_destroy(&kvm_total_used_mmu_pages);
 	unregister_shrinker(&mmu_shrinker);
 }
 
@@ -3207,7 +3208,9 @@ int kvm_mmu_module_init(void)
 	if (!mmu_page_header_cache)
 		goto nomem;
 
-	percpu_counter_init(&kvm_total_used_mmu_pages, 0);
+	if (percpu_counter_init(&kvm_total_used_mmu_pages, 0))
+		goto nomem;
+
 	register_shrinker(&mmu_shrinker);
 
 	return 0;