From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>

Fix get_apic_id() in mach-default, so that it uses 8 bits incase of xAPIC case
and 4 bits for legacy APIC case.

This fixes the i386 kernel assumption that apic id is less than 16 for xAPIC
platforms with 8 cpus or less and makes the kernel boot on such platforms.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/asm-i386/mach-default/mach_apicdef.h |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletion(-)

diff -puN include/asm-i386/mach-default/mach_apicdef.h~i386-apic-fix-4-bit-apicid-assumption-of-mach-default include/asm-i386/mach-default/mach_apicdef.h
--- a/include/asm-i386/mach-default/mach_apicdef.h~i386-apic-fix-4-bit-apicid-assumption-of-mach-default
+++ a/include/asm-i386/mach-default/mach_apicdef.h
@@ -1,11 +1,17 @@
 #ifndef __ASM_MACH_APICDEF_H
 #define __ASM_MACH_APICDEF_H
 
+#include <asm/apic.h>
+
 #define		APIC_ID_MASK		(0xF<<24)
 
 static inline unsigned get_apic_id(unsigned long x) 
 { 
-	return (((x)>>24)&0xF);
+	unsigned int ver = GET_APIC_VERSION(apic_read(APIC_LVR));
+	if (APIC_XAPIC(ver))
+		return (((x)>>24)&0xFF);
+	else
+		return (((x)>>24)&0xF);
 } 
 
 #define		GET_APIC_ID(x)	get_apic_id(x)
_