diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h
index 12080d87da3b1..2e781bcc5e12d 100644
--- a/arch/x86/include/asm/desc.h
+++ b/arch/x86/include/asm/desc.h
@@ -177,16 +177,8 @@ static inline void __set_tss_desc(unsigned cpu, unsigned int entry, void *addr)
 	struct desc_struct *d = get_cpu_gdt_table(cpu);
 	tss_desc tss;
 
-	/*
-	 * sizeof(unsigned long) coming from an extra "long" at the end
-	 * of the iobitmap. See tss_struct definition in processor.h
-	 *
-	 * -1? seg base+limit should be pointing to the address of the
-	 * last valid byte
-	 */
 	set_tssldt_descriptor(&tss, (unsigned long)addr, DESC_TSS,
-			      IO_BITMAP_OFFSET + IO_BITMAP_BYTES +
-			      sizeof(unsigned long) - 1);
+			      __KERNEL_TSS_LIMIT);
 	write_gdt_entry(d, entry, &tss, DESC_TSS);
 }
 
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 1be64da0384ed..f8f1b7537abee 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -341,6 +341,16 @@ struct tss_struct {
 
 DECLARE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss);
 
+/*
+ * sizeof(unsigned long) coming from an extra "long" at the end
+ * of the iobitmap.
+ *
+ * -1? seg base+limit should be pointing to the address of the
+ * last valid byte
+ */
+#define __KERNEL_TSS_LIMIT	\
+	(IO_BITMAP_OFFSET + IO_BITMAP_BYTES + sizeof(unsigned long) - 1)
+
 #ifdef CONFIG_X86_32
 DECLARE_PER_CPU(unsigned long, cpu_current_top_of_stack);
 #endif