x86: add generic clearcpuid=... option

Add a generic option to clear any cpuid bit. I added it because it was
very easy to add with the new generic cpuid disable bitmap and perhaps
it will be useful in the future.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 56b7ea8..56cc341 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -572,6 +572,17 @@
 		printk("\n");
 }
 
+static __init int setup_disablecpuid(char *arg)
+{
+	int bit;
+	if (get_option(&arg, &bit) && bit < NCAPINTS*32)
+		setup_clear_cpu_cap(bit);
+	else
+		return 0;
+	return 1;
+}
+__setup("clearcpuid=", setup_disablecpuid);
+
 cpumask_t cpu_initialized __cpuinitdata = CPU_MASK_NONE;
 
 /* This is hacky. :)