x86, intel: Output microcode revision in /proc/cpuinfo

I got a request to make it easier to determine the microcode
update level on Intel CPUs. This patch adds a new "microcode"
field to /proc/cpuinfo.

The microcode level is also outputed on fatal machine checks
together with the other CPUID model information.

I removed the respective code from the microcode update driver,
it just reads the field from cpu_data. Also when the microcode
is updated it fills in the new values too.

I had to add a memory barrier to native_cpuid to prevent it
being optimized away when the result is not used.

This turns out to clean up further code which already got this
information manually. This is done in followon patches.

Signed-off-by: Andi Kleen <[e-mail]>
Acked-by: H. Peter Anvin <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/include/asm/processor.h

···
 	/* Index into per_cpu list: */
 	u16			cpu_index;
 #endif
+	u32			microcode;
 } __attribute__((__aligned__(SMP_CACHE_BYTES)));
 
 #define X86_VENDOR_INTEL	0
···
 	      "=b" (*ebx),
 	      "=c" (*ecx),
 	      "=d" (*edx)
-	    : "0" (*eax), "2" (*ecx));
+	    : "0" (*eax), "2" (*ecx)
+	    : "memory");
 }
 
 static inline void load_cr3(pgd_t *pgdir)

arch/x86/kernel/cpu/intel.c

···
 		(c->x86 == 0x6 && c->x86_model >= 0x0e))
 		set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
 
+	if (c->x86 >= 6 && !cpu_has(c, X86_FEATURE_IA64)) {
+		unsigned lower_word;
+
+		wrmsr(MSR_IA32_UCODE_REV, 0, 0);
+		/* Required by the SDM */
+		sync_core();
+		rdmsr(MSR_IA32_UCODE_REV, lower_word, c->microcode);
+	}
+
 	/*
 	 * Atom erratum AAE44/AAF40/AAG38/AAH41:
 	 *

arch/x86/kernel/cpu/mcheck/mce.c

···
 		pr_cont("MISC %llx ", m->misc);
 
 	pr_cont("\n");
-	pr_emerg(HW_ERR "PROCESSOR %u:%x TIME %llu SOCKET %u APIC %x\n",
-		m->cpuvendor, m->cpuid, m->time, m->socketid, m->apicid);
+	/*
+	 * Note this output is parsed by external tools and old fields
+	 * should not be changed.
+	 */
+	pr_emerg(HW_ERR "PROCESSOR %u:%x TIME %llu SOCKET %u APIC %x microcode %u\n",
+		m->cpuvendor, m->cpuid, m->time, m->socketid, m->apicid,
+		cpu_data(m->extcpu).microcode);
 
 	/*
 	 * Print out human-readable details about the MCE error,

arch/x86/kernel/cpu/proc.c

···
 		seq_printf(m, "stepping\t: %d\n", c->x86_mask);
 	else
 		seq_printf(m, "stepping\t: unknown\n");
+	if (c->microcode)
+		seq_printf(m, "microcode\t: %u\n", c->microcode);
 
 	if (cpu_has(c, X86_FEATURE_TSC)) {
 		unsigned int freq = cpufreq_quick_get(cpu);

arch/x86/kernel/microcode_intel.c

···
 		csig->pf = 1 << ((val[1] >> 18) & 7);
 	}
 
-	wrmsr(MSR_IA32_UCODE_REV, 0, 0);
-	/* see notes above for revision 1.07.  Apparent chip bug */
-	sync_core();
-	/* get the current revision from MSR 0x8B */
-	rdmsr(MSR_IA32_UCODE_REV, val[0], csig->rev);
-
+	csig->rev = c->microcode;
 	pr_info("CPU%d sig=0x%x, pf=0x%x, revision=0x%x\n",
 		cpu_num, csig->sig, csig->pf, csig->rev);
 
···
 	struct microcode_intel *mc_intel;
 	struct ucode_cpu_info *uci;
 	unsigned int val[2];
-	int cpu_num;
+	int cpu_num = raw_smp_processor_id();
+	struct cpuinfo_x86 *c = &cpu_data(cpu_num);
 
-	cpu_num = raw_smp_processor_id();
 	uci = ucode_cpu_info + cpu;
 	mc_intel = uci->mc;
 
···
 	      (unsigned long) mc_intel->bits >> 16 >> 16);
 	wrmsr(MSR_IA32_UCODE_REV, 0, 0);
 
-	/* see notes above for revision 1.07.  Apparent chip bug */
+	/* As documented in the SDM: Do a CPUID 1 here */
 	sync_core();
 
 	/* get the current revision from MSR 0x8B */
···
 		(mc_intel->hdr.date >> 16) & 0xff);
 
 	uci->cpu_sig.rev = val[1];
+	c->microcode = val[1];
 
 	return 0;
 }