x86/CPU: Add native CPUID variants returning a single datum

... similarly to the cpuid_<reg>() variants.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20170109114147.5082-2-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/processor.h

@@ -219,6 +219,24 @@ static inline void native_cpuid(unsigned int *eax, unsigned int *ebx,
 	    : "memory");
 }
 
+#define native_cpuid_reg(reg)					\
+static inline unsigned int native_cpuid_##reg(unsigned int op)	\
+{								\
+	unsigned int eax = op, ebx, ecx = 0, edx;		\
+								\
+	native_cpuid(&eax, &ebx, &ecx, &edx);			\
+								\
+	return reg;						\
+}
+
+/*
+ * Native CPUID functions returning a single datum.
+ */
+native_cpuid_reg(eax)
+native_cpuid_reg(ebx)
+native_cpuid_reg(ecx)
+native_cpuid_reg(edx)
+
 static inline void load_cr3(pgd_t *pgdir)
 {
 	write_cr3(__pa(pgdir));