diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 615897c..fe24c32 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -116,13 +116,17 @@ static void xen_vcpu_setup(int cpu)
 	struct vcpu_info *vcpup;
 
 	BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
-	per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
 
-	if (!have_vcpu_info_placement)
-		return;		/* already tested, not available */
+	if (cpu < MAX_VIRT_CPUS)
+		per_cpu(xen_vcpu,cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
 
-	vcpup = &per_cpu(xen_vcpu_info, cpu);
+	if (!have_vcpu_info_placement) {
+		if (cpu >= MAX_VIRT_CPUS && setup_max_cpus > MAX_VIRT_CPUS)
+			setup_max_cpus = MAX_VIRT_CPUS;
+		return;
+	}
 
+	vcpup = &per_cpu(xen_vcpu_info, cpu);
 	info.mfn = arbitrary_virt_to_mfn(vcpup);
 	info.offset = offset_in_page(vcpup);
 
@@ -137,6 +141,8 @@ static void xen_vcpu_setup(int cpu)
 	if (err) {
 		printk(KERN_DEBUG "register_vcpu_info failed: err=%d\n", err);
 		have_vcpu_info_placement = 0;
+		if (setup_max_cpus > MAX_VIRT_CPUS)
+			setup_max_cpus = MAX_VIRT_CPUS;
 	} else {
 		/* This cpu is using the registered vcpu info, even if
 		   later ones fail to. */