linux-kernel - [PATCH v2 1/1] x86: Use x2apic physical mode based on FADT setting

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Message-Id: <1335313436-32020-1-git-send-email-greg.pearson@hp.com>
Date:	Tue, 24 Apr 2012 18:23:56 -0600
From:	Greg Pearson <greg.pearson@...com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel@...r.kernel.org, Greg Pearson <greg.pearson@...com>
Subject: [PATCH v2 1/1] x86: 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@...com>
---
 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;
 }
-- 
1.7.5.4

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