diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 729573b844e5e860d4d108f68c5889f2d849ebc6..93ecafbfb1b6bfdeb147f671ebecd3b5988e244c 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -333,26 +333,13 @@ int __kvm_set_memory_region(struct kvm *kvm,
 	if (mem->slot >= kvm->nmemslots)
 		kvm->nmemslots = mem->slot + 1;
 
+	*memslot = new;
+
 	if (!kvm->n_requested_mmu_pages) {
-		unsigned int n_pages;
-
-		if (npages) {
-			n_pages = npages * KVM_PERMILLE_MMU_PAGES / 1000;
-			kvm_mmu_change_mmu_pages(kvm, kvm->n_alloc_mmu_pages +
-						 n_pages);
-		} else {
-			unsigned int nr_mmu_pages;
-
-			n_pages = old.npages * KVM_PERMILLE_MMU_PAGES / 1000;
-			nr_mmu_pages = kvm->n_alloc_mmu_pages - n_pages;
-			nr_mmu_pages = max(nr_mmu_pages,
-				        (unsigned int) KVM_MIN_ALLOC_MMU_PAGES);
-			kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages);
-		}
+		unsigned int nr_mmu_pages = kvm_mmu_calculate_mmu_pages(kvm);
+		kvm_mmu_change_mmu_pages(kvm, nr_mmu_pages);
 	}
 
-	*memslot = new;
-
 	kvm_mmu_slot_remove_write_access(kvm, mem->slot);
 	kvm_flush_remote_tlbs(kvm);
 
diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
index 4624f3789b9a8df1d6ad490fee317dd564c44455..101cd5377a89716377021baebe68733b14e5ca85 100644
--- a/drivers/kvm/mmu.c
+++ b/drivers/kvm/mmu.c
@@ -1535,6 +1535,25 @@ int kvm_mmu_module_init(void)
 	return -ENOMEM;
 }
 
+/*
+ * Caculate mmu pages needed for kvm.
+ */
+unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
+{
+	int i;
+	unsigned int nr_mmu_pages;
+	unsigned int  nr_pages = 0;
+
+	for (i = 0; i < kvm->nmemslots; i++)
+		nr_pages += kvm->memslots[i].npages;
+
+	nr_mmu_pages = nr_pages * KVM_PERMILLE_MMU_PAGES / 1000;
+	nr_mmu_pages = max(nr_mmu_pages,
+			(unsigned int) KVM_MIN_ALLOC_MMU_PAGES);
+
+	return nr_mmu_pages;
+}
+
 #ifdef AUDIT
 
 static const char *audit_msg;
diff --git a/drivers/kvm/x86.h b/drivers/kvm/x86.h
index 90b791bf62879a64471902c33f06878cadcb5295..71f2477d03fd18c9ce258c62ccaaa0bf3c52197d 100644
--- a/drivers/kvm/x86.h
+++ b/drivers/kvm/x86.h
@@ -236,6 +236,7 @@ void kvm_mmu_set_nonpresent_ptes(u64 trap_pte, u64 notrap_pte);
 int kvm_mmu_reset_context(struct kvm_vcpu *vcpu);
 void kvm_mmu_slot_remove_write_access(struct kvm *kvm, int slot);
 void kvm_mmu_zap_all(struct kvm *kvm);
+unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm);
 void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned int kvm_nr_mmu_pages);
 
 enum emulation_result {