i386: Clear MCE flag on AMD K6

It reports machine check capability in CPUID, but doesn't actually
implement all the necessary MSRs of the standard Intel machine
check architecture.

This fixes a boot failure on K6s recently introduced.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/kernel/cpu/amd.c

@@ -280,6 +280,10 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 
 	if (c->x86 == 0x10 && !force_mwait)
 		clear_bit(X86_FEATURE_MWAIT, c->x86_capability);
+
+	/* K6s reports MCEs but don't actually have all the MSRs */
+	if (c->x86 < 6)
+		clear_bit(X86_FEATURE_MCE, c->x86_capability);
 }
 
 static unsigned int __cpuinit amd_size_cache(struct cpuinfo_x86 * c, unsigned int size)

arch/i386/kernel/cpu/mcheck/k7.c

@@ -72,12 +72,12 @@ void amd_mcheck_init(struct cpuinfo_x86 *c)
 	u32 l, h;
 	int i;
 
-	machine_check_vector = k7_machine_check;
-	wmb();
-
 	if (!cpu_has(c, X86_FEATURE_MCE))
 		return;
 
+	machine_check_vector = k7_machine_check;
+	wmb();
+
 	printk (KERN_INFO "Intel machine check architecture supported.\n");
 	rdmsr (MSR_IA32_MCG_CAP, l, h);
 	if (l & (1<<8))	/* Control register present ? */