commit 58d5fa7a6a6fc4754d295d0999b284edd67c8620
Author: Siddha, Suresh B <suresh.b.siddha@intel.com>
Date:   Wed Oct 17 18:04:33 2007 +0200

    i386: fix 4 bit apicid assumption of mach-default
    
    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.
    
    [ tglx: arch/x86 adaptation ]
    
    Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    Signed-off-by: Andi Kleen <ak@suse.de>
    Cc: Andi Kleen <ak@suse.de>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/include/asm-i386/mach-default/mach_apicdef.h b/include/asm-i386/mach-default/mach_apicdef.h
index 7bcb350..ae98413 100644
--- a/include/asm-i386/mach-default/mach_apicdef.h
+++ b/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)