Index: head-2005-12-07/arch/x86_64/kernel/mpparse-xen.c
===================================================================
--- head-2005-12-07.orig/arch/x86_64/kernel/mpparse-xen.c	2005-12-07 10:58:34.000000000 +0100
+++ head-2005-12-07/arch/x86_64/kernel/mpparse-xen.c	2005-12-14 14:30:45.000000000 +0100
@@ -174,8 +174,14 @@ static void __init MP_processor_info (st
 	cpu_set(cpu, cpu_present_map);
 }
 #else
-void __init MP_processor_info (struct mpc_config_processor *m)
+static void __init MP_processor_info (struct mpc_config_processor *m)
 {
+	if (num_processors >= NR_CPUS) {
+		printk(KERN_WARNING "WARNING: NR_CPUS limit of %i reached."
+			" Processor ignored.\n", NR_CPUS);
+		return;
+	}
+	cpu_set(num_processors, cpu_possible_map);
 	num_processors++;
 }
 #endif /* CONFIG_XEN */
Index: head-2005-12-07/drivers/xen/core/smpboot.c
===================================================================
--- head-2005-12-07.orig/drivers/xen/core/smpboot.c	2005-12-07 10:58:40.000000000 +0100
+++ head-2005-12-07/drivers/xen/core/smpboot.c	2005-12-14 13:52:11.000000000 +0100
@@ -272,9 +272,9 @@ void __init smp_prepare_cpus(unsigned in
 
 void __devinit smp_prepare_boot_cpu(void)
 {
-	cpu_possible_map = cpumask_of_cpu(0);
-	cpu_present_map  = cpumask_of_cpu(0);
-	cpu_online_map   = cpumask_of_cpu(0);
+	cpu_set(0, cpu_possible_map);
+	cpu_set(0, cpu_present_map);
+	cpu_set(0, cpu_online_map);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU