[tip:x86/urgent] x86/apic: Use x2apic physical mode based on FADT setting

[tip-bot for Greg Pearson <greg.pearson@hp.com>]

Commit-ID:  ea0dcf903e7d76aa5d483d876215fedcfdfe140f
Gitweb:     http://git.kernel.org/tip/ea0dcf903e7d76aa5d483d876215fedcfdfe140f
Author:     Greg Pearson <greg.pearson@hp.com>
AuthorDate: Tue, 24 Apr 2012 18:23:56 -0600
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 25 Apr 2012 12:47:08 +0200

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>
---
 arch/x86/kernel/apic/x2apic_phys.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
index 8a778db..991e315 100644
--- 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;
 }