diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index cfcdaace12..8a35a5affe 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -624,7 +624,11 @@ bool detect_extended_topology(struct cpuinfo_x86 *c)
 	if ( c->cpuid_level < 0xb )
 		return false;
 
+	printk("dbg smp_processor_id() = %u\n", smp_processor_id());
+	printk("dbg get_apic_id() = %u\n", get_apic_id());
+
 	cpuid_count(0xb, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
+	printk("dbg cpuid_count(0xb, SMT_LEVEL) = %#x, %#x, %#x, %#x\n", eax, ebx, ecx, edx);
 
 	/* Check if the cpuid leaf 0xb is actually implemented */
 	if ( ebx == 0 || (LEAFB_SUBTYPE(ecx) != SMT_TYPE) )
@@ -641,6 +645,7 @@ bool detect_extended_topology(struct cpuinfo_x86 *c)
 	sub_index = 1;
 	do {
 		cpuid_count(0xb, sub_index, &eax, &ebx, &ecx, &edx);
+		printk("dbg cpuid_count(0xb, %#x) = %#x, %#x, %#x, %#x\n", sub_index, eax, ebx, ecx, edx);
 
 		/* Check for the Core type in the implemented sub leaves */
 		if ( LEAFB_SUBTYPE(ecx) == CORE_TYPE ) {