Index: kvm/arch/ia64/kvm/kvm-ia64.c
===================================================================
--- kvm.orig/arch/ia64/kvm/kvm-ia64.c
+++ kvm/arch/ia64/kvm/kvm-ia64.c
@@ -1576,15 +1576,14 @@ out:
 	return r;
 }
 
-int kvm_arch_set_memory_region(struct kvm *kvm,
-		struct kvm_userspace_memory_region *mem,
+int kvm_arch_prepare_memory_region(struct kvm *kvm,
+		struct kvm_memory_slot *memslot,
 		struct kvm_memory_slot old,
 		int user_alloc)
 {
 	unsigned long i;
 	unsigned long pfn;
-	int npages = mem->memory_size >> PAGE_SHIFT;
-	struct kvm_memory_slot *memslot = &kvm->memslots[mem->slot];
+	int npages = memslot->npages;
 	unsigned long base_gfn = memslot->base_gfn;
 
 	if (base_gfn + npages > (KVM_MAX_MEM_SIZE >> PAGE_SHIFT))
@@ -1608,6 +1607,14 @@ int kvm_arch_set_memory_region(struct kv
 	return 0;
 }
 
+void kvm_arch_commit_memory_region(struct kvm *kvm,
+		struct kvm_userspace_memory_region *mem,
+		struct kvm_memory_slot old,
+		int user_alloc)
+{
+	return;
+}
+
 void kvm_arch_flush_shadow(struct kvm *kvm)
 {
 	kvm_flush_remote_tlbs(kvm);
Index: kvm/arch/s390/kvm/kvm-s390.c
===================================================================
--- kvm.orig/arch/s390/kvm/kvm-s390.c
+++ kvm/arch/s390/kvm/kvm-s390.c
@@ -689,10 +689,10 @@ long kvm_arch_vcpu_ioctl(struct file *fi
 }
 
 /* Section: memory related */
-int kvm_arch_set_memory_region(struct kvm *kvm,
-				struct kvm_userspace_memory_region *mem,
-				struct kvm_memory_slot old,
-				int user_alloc)
+int kvm_arch_prepare_memory_region(struct kvm *kvm,
+				   struct kvm_userspace_memory_region *mem,
+				   struct kvm_memory_slot old,
+				   int user_alloc)
 {
 	int i;
 	struct kvm_vcpu *vcpu;
@@ -719,14 +719,20 @@ int kvm_arch_set_memory_region(struct kv
 	if (!user_alloc)
 		return -EINVAL;
 
+	return 0;
+}
+
+int kvm_arch_commit_memory_region(struct kvm *kvm,
+				struct kvm_userspace_memory_region *mem,
+				struct kvm_memory_slot old,
+				int user_alloc)
+{
 	/* request update of sie control block for all available vcpus */
 	kvm_for_each_vcpu(i, vcpu, kvm) {
 		if (test_and_set_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests))
 			continue;
 		kvm_s390_inject_sigp_stop(vcpu, ACTION_RELOADVCPU_ON_STOP);
 	}
-
-	return 0;
 }
 
 void kvm_arch_flush_shadow(struct kvm *kvm)
Index: kvm/arch/x86/kvm/x86.c
===================================================================
--- kvm.orig/arch/x86/kvm/x86.c
+++ kvm/arch/x86/kvm/x86.c
@@ -5227,13 +5227,12 @@ void kvm_arch_destroy_vm(struct kvm *kvm
 	kfree(kvm);
 }
 
-int kvm_arch_set_memory_region(struct kvm *kvm,
-				struct kvm_userspace_memory_region *mem,
+int kvm_arch_prepare_memory_region(struct kvm *kvm,
+				struct kvm_memory_slot *memslot,
 				struct kvm_memory_slot old,
 				int user_alloc)
 {
-	int npages = mem->memory_size >> PAGE_SHIFT;
-	struct kvm_memory_slot *memslot = &kvm->memslots->memslots[mem->slot];
+	int npages = memslot->npages;
 
 	/*To keep backward compatibility with older userspace,
 	 *x86 needs to hanlde !user_alloc case.
@@ -5253,26 +5252,35 @@ int kvm_arch_set_memory_region(struct kv
 			if (IS_ERR((void *)userspace_addr))
 				return PTR_ERR((void *)userspace_addr);
 
-			/* set userspace_addr atomically for kvm_hva_to_rmapp */
-			spin_lock(&kvm->mmu_lock);
 			memslot->userspace_addr = userspace_addr;
-			spin_unlock(&kvm->mmu_lock);
-		} else {
-			if (!old.user_alloc && old.rmap) {
-				int ret;
-
-				down_write(&current->mm->mmap_sem);
-				ret = do_munmap(current->mm, old.userspace_addr,
-						old.npages * PAGE_SIZE);
-				up_write(&current->mm->mmap_sem);
-				if (ret < 0)
-					printk(KERN_WARNING
-				       "kvm_vm_ioctl_set_memory_region: "
-				       "failed to munmap memory\n");
-			}
 		}
 	}
 
+
+	return 0;
+}
+
+void kvm_arch_commit_memory_region(struct kvm *kvm,
+				struct kvm_userspace_memory_region *mem,
+				struct kvm_memory_slot old,
+				int user_alloc)
+{
+
+	int npages = mem->memory_size >> PAGE_SHIFT;
+
+	if (!user_alloc && !old.user_alloc && old.rmap && !npages) {
+		int ret;
+
+		down_write(&current->mm->mmap_sem);
+		ret = do_munmap(current->mm, old.userspace_addr,
+				old.npages * PAGE_SIZE);
+		up_write(&current->mm->mmap_sem);
+		if (ret < 0)
+			printk(KERN_WARNING
+			       "kvm_vm_ioctl_set_memory_region: "
+			       "failed to munmap memory\n");
+	}
+
 	spin_lock(&kvm->mmu_lock);
 	if (!kvm->arch.n_requested_mmu_pages) {
 		unsigned int nr_mmu_pages = kvm_mmu_calculate_mmu_pages(kvm);
@@ -5281,8 +5289,6 @@ int kvm_arch_set_memory_region(struct kv
 
 	kvm_mmu_slot_remove_write_access(kvm, mem->slot);
 	spin_unlock(&kvm->mmu_lock);
-
-	return 0;
 }
 
 void kvm_arch_flush_shadow(struct kvm *kvm)
Index: kvm/include/linux/kvm_host.h
===================================================================
--- kvm.orig/include/linux/kvm_host.h
+++ kvm/include/linux/kvm_host.h
@@ -253,7 +253,11 @@ int kvm_set_memory_region(struct kvm *kv
 int __kvm_set_memory_region(struct kvm *kvm,
 			    struct kvm_userspace_memory_region *mem,
 			    int user_alloc);
-int kvm_arch_set_memory_region(struct kvm *kvm,
+int kvm_arch_prepare_memory_region(struct kvm *kvm,
+				struct kvm_memory_slot *memslot,
+				struct kvm_memory_slot old,
+				int user_alloc);
+void kvm_arch_commit_memory_region(struct kvm *kvm,
 				struct kvm_userspace_memory_region *mem,
 				struct kvm_memory_slot old,
 				int user_alloc);
Index: kvm/virt/kvm/kvm_main.c
===================================================================
--- kvm.orig/virt/kvm/kvm_main.c
+++ kvm/virt/kvm/kvm_main.c
@@ -663,6 +663,10 @@ skip_lpage:
 	if (!npages)
 		kvm_arch_flush_shadow(kvm);
 
+	r = kvm_arch_prepare_memory_region(kvm, &new, old, user_alloc);
+	if (r)
+		goto out_free;
+
 	spin_lock(&kvm->mmu_lock);
 	if (mem->slot >= kvm->memslots->nmemslots)
 		kvm->memslots->nmemslots = mem->slot + 1;
@@ -670,13 +674,7 @@ skip_lpage:
 	*memslot = new;
 	spin_unlock(&kvm->mmu_lock);
 
-	r = kvm_arch_set_memory_region(kvm, mem, old, user_alloc);
-	if (r) {
-		spin_lock(&kvm->mmu_lock);
-		*memslot = old;
-		spin_unlock(&kvm->mmu_lock);
-		goto out_free;
-	}
+	kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);
 
 	kvm_free_physmem_slot(&old, npages ? &new : NULL);
 	/* Slot deletion case: we have to update the current slot */
