x86/microcode/intel: Add a helper which gives the microcode revision

Since on Intel we're required to do CPUID(1) first, before reading
the microcode revision MSR, let's add a special helper which does the
required steps so that we don't forget to do them next time, when we
want to read the microcode revision.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20170109114147.5082-4-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/microcode_intel.h

@@ -52,6 +52,21 @@ struct extended_sigtable {
 
 #define exttable_size(et) ((et)->count * EXT_SIGNATURE_SIZE + EXT_HEADER_SIZE)
 
+static inline u32 intel_get_microcode_revision(void)
+{
+	u32 rev, dummy;
+
+	native_wrmsrl(MSR_IA32_UCODE_REV, 0);
+
+	/* As documented in the SDM: Do a CPUID 1 here */
+	native_cpuid_eax(1);
+
+	/* get the current revision from MSR 0x8B */
+	native_rdmsr(MSR_IA32_UCODE_REV, dummy, rev);
+
+	return rev;
+}
+
 #ifdef CONFIG_MICROCODE_INTEL
 extern void __init load_ucode_intel_bsp(void);
 extern void load_ucode_intel_ap(void);

arch/x86/kernel/cpu/intel.c

@@ -14,6 +14,7 @@
 #include <asm/bugs.h>
 #include <asm/cpu.h>
 #include <asm/intel-family.h>
+#include <asm/microcode_intel.h>
 
 #ifdef CONFIG_X86_64
 #include <linux/topology.h>
@@ -78,14 +79,8 @@ static void early_init_intel(struct cpuinfo_x86 *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 */
-		native_cpuid_eax(1);
-		rdmsr(MSR_IA32_UCODE_REV, lower_word, c->microcode);
-	}
+	if (c->x86 >= 6 && !cpu_has(c, X86_FEATURE_IA64))
+		c->microcode = intel_get_microcode_revision();
 
 	/*
 	 * Atom erratum AAE44/AAF40/AAG38/AAH41:

arch/x86/kernel/cpu/microcode/intel.c

@@ -390,15 +390,8 @@ static int collect_cpu_info_early(struct ucode_cpu_info *uci)
 		native_rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
 		csig.pf = 1 << ((val[1] >> 18) & 7);
 	}
-	native_wrmsrl(MSR_IA32_UCODE_REV, 0);
 
-	/* As documented in the SDM: Do a CPUID 1 here */
-	native_cpuid_eax(1);
-
-	/* get the current revision from MSR 0x8B */
-	native_rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
-
-	csig.rev = val[1];
+	csig.rev = intel_get_microcode_revision();
 
 	uci->cpu_sig = csig;
 	uci->valid = 1;
@@ -582,7 +575,7 @@ static inline void print_ucode(struct ucode_cpu_info *uci)
 static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 {
 	struct microcode_intel *mc;
-	unsigned int val[2];
+	u32 rev;
 
 	mc = uci->mc;
 	if (!mc)
@@ -590,21 +583,16 @@ static int apply_microcode_early(struct ucode_cpu_info *uci, bool early)
 
 	/* write microcode via MSR 0x79 */
 	native_wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
-	native_wrmsrl(MSR_IA32_UCODE_REV, 0);
 
-	/* As documented in the SDM: Do a CPUID 1 here */
-	native_cpuid_eax(1);
-
-	/* get the current revision from MSR 0x8B */
-	native_rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
-	if (val[1] != mc->hdr.rev)
+	rev = intel_get_microcode_revision();
+	if (rev != mc->hdr.rev)
 		return -1;
 
 #ifdef CONFIG_X86_64
 	/* Flush global tlb. This is precaution. */
 	flush_tlb_early();
 #endif
-	uci->cpu_sig.rev = val[1];
+	uci->cpu_sig.rev = rev;
 
 	if (early)
 		print_ucode(uci);
@@ -784,8 +772,8 @@ static int apply_microcode_intel(int cpu)
 	struct microcode_intel *mc;
 	struct ucode_cpu_info *uci;
 	struct cpuinfo_x86 *c;
-	unsigned int val[2];
 	static int prev_rev;
+	u32 rev;
 
 	/* We should bind the task to the CPU */
 	if (WARN_ON(raw_smp_processor_id() != cpu))
@@ -802,33 +790,28 @@ static int apply_microcode_intel(int cpu)
 
 	/* write microcode via MSR 0x79 */
 	wrmsrl(MSR_IA32_UCODE_WRITE, (unsigned long)mc->bits);
-	wrmsrl(MSR_IA32_UCODE_REV, 0);
-
-	/* As documented in the SDM: Do a CPUID 1 here */
-	native_cpuid_eax(1);
 
-	/* get the current revision from MSR 0x8B */
-	rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]);
+	rev = intel_get_microcode_revision();
 
-	if (val[1] != mc->hdr.rev) {
+	if (rev != mc->hdr.rev) {
 		pr_err("CPU%d update to revision 0x%x failed\n",
 		       cpu, mc->hdr.rev);
 		return -1;
 	}
 
-	if (val[1] != prev_rev) {
+	if (rev != prev_rev) {
 		pr_info("updated to revision 0x%x, date = %04x-%02x-%02x\n",
-			val[1],
+			rev,
 			mc->hdr.date & 0xffff,
 			mc->hdr.date >> 24,
 			(mc->hdr.date >> 16) & 0xff);
-		prev_rev = val[1];
+		prev_rev = rev;
 	}
 
 	c = &cpu_data(cpu);
 
-	uci->cpu_sig.rev = val[1];
-	c->microcode = val[1];
+	uci->cpu_sig.rev = rev;
+	c->microcode = rev;
 
 	return 0;
 }