x86/apic: Use x2apic physical mode based on FADT setting

Provide systems that do not support x2apic cluster mode
a mechanism to select x2apic physical mode using the
FADT FORCE_APIC_PHYSICAL_DESTINATION_MODE bit.

Changes from v1: (based on Suresh's comments)
 - removed #ifdef CONFIG_ACPI
 - removed #include <linux/acpi.h>

Signed-off-by: Greg Pearson <greg.pearson@hp.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/r/1335313436-32020-1-git-send-email-greg.pearson@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
index 8a778db..991e315 100644 (file)
--- a/arch/x86/kernel/apic/x2apic_phys.c
+++ b/arch/x86/kernel/apic/x2apic_phys.c
@@ -24,6 +24,12 @@ static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 {
        if (x2apic_phys)
                return x2apic_enabled();
+       else if ((acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) &&
+               (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL) &&
+               x2apic_enabled()) {
+               printk(KERN_DEBUG "System requires x2apic physical mode\n");
+               return 1;
+       }
        else
                return 0;
 }