Index: head-2006-08-08/drivers/xen/core/smpboot.c
===================================================================
--- head-2006-08-08.orig/drivers/xen/core/smpboot.c	2006-08-11 15:33:05.000000000 +0200
+++ head-2006-08-08/drivers/xen/core/smpboot.c	2006-08-11 15:34:19.000000000 +0200
@@ -253,6 +253,8 @@ void __init smp_prepare_cpus(unsigned in
 	for_each_cpu_mask (cpu, cpu_possible_map) {
 		if (cpu == 0)
 			continue;
+		if (num_present_cpus() >= max_cpus)
+			break;
 
 #ifdef __x86_64__
 		gdt_descr = &cpu_gdt_descr[cpu];
@@ -301,7 +303,7 @@ void __init smp_prepare_cpus(unsigned in
 	init_xenbus_allowed_cpumask();
 
 	/* Currently, Xen gives no dynamic NUMA/HT info. */
-	for (cpu = 1; cpu < NR_CPUS; cpu++) {
+	for_each_present_cpu(cpu) {
 		cpu_sibling_map[cpu] = cpumask_of_cpu(cpu);
 		cpu_core_map[cpu]    = cpumask_of_cpu(cpu);
 	}