[ 042/153] x86/apic: Use x2apic physical mode based on FADT setting

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Greg Pearson <greg.pearson@xxxxxx>

commit ea0dcf903e7d76aa5d483d876215fedcfdfe140f upstream.

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@xxxxxx>
Acked-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1335313436-32020-1-git-send-email-greg.pearson@xxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/x2apic_phys.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- 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(ch
 {
 	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;
 }


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