x86, irq: don't call mp_config_acpi_gsi() if update_mptable is not enabled

Len expressed concern that the update_mptable feature has
side-effects on the ACPI code.

Make it sure explicitly that the code only ever gets called if
the (default disabled) update_mptable boot quirk option is
disabled.

[ Impact: isolate the update_mptable feature from ACPI code more ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Len Brown <lenb@kernel.org>
LKML-Reference: <4A0DC832.5090200@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/mpspec.h

@@ -87,6 +87,15 @@ static inline int acpi_probe_gsi(void)
 }
 #endif /* CONFIG_ACPI */
 
+#ifdef CONFIG_X86_MPPARSE
+extern int enable_update_mptable;
+#else
+static inline int enable_update_mptable(void)
+{
+	return 0;
+}
+#endif
+
 #define PHYSID_ARRAY_SIZE	BITS_TO_LONGS(MAX_APICS)
 
 struct physid_mask {

arch/x86/kernel/acpi/boot.c

@@ -1226,7 +1226,9 @@ int mp_register_gsi(struct device *dev, u32 gsi, int trigger, int polarity)
 		       ioapic_pin);
 		return gsi;
 	}
-	mp_config_acpi_gsi(dev, gsi, trigger, polarity);
+
+	if (enable_update_mptable)
+		mp_config_acpi_gsi(dev, gsi, trigger, polarity);
 
 	set_io_apic_irq_attr(&irq_attr, ioapic, ioapic_pin,
 			     trigger == ACPI_EDGE_SENSITIVE ? 0 : 1,

arch/x86/kernel/mpparse.c

@@ -957,7 +957,7 @@ out:
 	return 0;
 }
 
-static int __initdata enable_update_mptable;
+int enable_update_mptable;
 
 static int __init update_mptable_setup(char *str)
 {