diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index 89edafb..f03b23e 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -31,4 +31,11 @@
 #endif
 
 DECLARE_PER_CPU(int, cpu_state);
+
+#ifdef CONFIG_X86_HAS_BOOT_CPU_ID
+extern unsigned char boot_cpu_id;
+#else
+#define boot_cpu_id				0
+#endif
+
 #endif /* _ASM_X86_CPU_H */