x86: add apic probe for genapic 64bit, v2

introducing an APIC handling probing abstraction:

 static struct genapic *apic_probe[] __initdata = {
	&apic_x2apic_uv_x,
	&apic_x2apic_phys,
	&apic_x2apic_cluster,
	&apic_physflat,
	NULL,
 };

This way we can remove UV, x2apic specific code from genapic_64.c and
move them to their specific genapic files.

[ v2: fix compiling when CONFIG_ACPI is not set ]

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/genx2apic_cluster.c b/arch/x86/kernel/genx2apic_cluster.c
index 40bc014..ef3f318 100644
--- a/arch/x86/kernel/genx2apic_cluster.c
+++ b/arch/x86/kernel/genx2apic_cluster.c
@@ -4,12 +4,22 @@
 #include <linux/kernel.h>
 #include <linux/ctype.h>
 #include <linux/init.h>
+#include <linux/dmar.h>
+
 #include <asm/smp.h>
 #include <asm/ipi.h>
 #include <asm/genapic.h>
 
 DEFINE_PER_CPU(u32, x86_cpu_to_logical_apicid);
 
+static int __init x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
+{
+	if (cpu_has_x2apic && intr_remapping_enabled)
+		return 1;
+
+	return 0;
+}
+
 /* Start with all IRQs pointing to boot CPU.  IRQ balancing will shift them. */
 
 static cpumask_t x2apic_target_cpus(void)
@@ -135,6 +145,7 @@
 
 struct genapic apic_x2apic_cluster = {
 	.name = "cluster x2apic",
+	.acpi_madt_oem_check = x2apic_acpi_madt_oem_check,
 	.int_delivery_mode = dest_LowestPrio,
 	.int_dest_mode = (APIC_DEST_LOGICAL != 0),
 	.target_cpus = x2apic_target_cpus,