x86/mce/therm_throt: allow disabling the thermal vector altogether

The thermal IRQ handler uses 1.21% CPU on my system when it's hot from
compiling things. Indeed looking at /proc/interrupts reveals quite a lot
of events coming in. Beyond logging them, the existing drivers on the
system don't appear to do very much that I'm interested in. So, add a
way to disable this entirely so that I can regain precious CPU cycles.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

arch/x86/Kconfig

@@ -1150,7 +1150,11 @@ config X86_MCE_INJECT
 
 config X86_THERMAL_VECTOR
 	def_bool y
+	prompt "Machine check thermal vector"
 	depends on X86_MCE_INTEL
+	---help---
+	  Provide support for capturing thermal events, logging them, and
+	  passing them off to other drivers.
 
 config X86_MCE_THERMAL_VERBOSE
 	bool "Verbose logging for thermal events"

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

@@ -511,7 +511,8 @@ static void intel_ppin_init(struct cpuinfo_x86 *c)
 
 void mce_intel_feature_init(struct cpuinfo_x86 *c)
 {
-	intel_init_thermal(c);
+	if (IS_ENABLED(CONFIG_X86_THERMAL_VECTOR))
+		intel_init_thermal(c);
 	intel_init_cmci();
 	intel_init_lmce();
 	intel_ppin_init(c);