diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 795c487..56689ef 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1377,6 +1377,8 @@
 
 	nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
 
+	nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
+
 	noltlbs		[PPC] Do not use large page/tlb entries for kernel
 			lowmem mapping on PPC40x.
 
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 785700a..8705262 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1337,7 +1337,9 @@
 				acpi_ioapic = 1;
 
 				smp_found_config = 1;
+#ifdef CONFIG_X86_32
 				setup_apic_routing();
+#endif
 			}
 		}
 		if (error == -EINVAL) {
diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index d5c0691..dd05010 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -27,6 +27,7 @@
 #include <linux/clockchips.h>
 #include <linux/acpi_pmtmr.h>
 #include <linux/module.h>
+#include <linux/dmar.h>
 
 #include <asm/atomic.h>
 #include <asm/smp.h>
@@ -39,6 +40,7 @@
 #include <asm/proto.h>
 #include <asm/timex.h>
 #include <asm/apic.h>
+#include <asm/i8259.h>
 
 #include <mach_ipi.h>
 #include <mach_apic.h>
@@ -46,8 +48,12 @@
 static int disable_apic_timer __cpuinitdata;
 static int apic_calibrate_pmtmr __initdata;
 int disable_apic;
+int disable_x2apic;
 int x2apic;
 
+/* x2apic enabled before OS handover */
+int x2apic_preenabled;
+
 /* Local APIC timer works in C2 */
 int local_apic_timer_c2_ok;
 EXPORT_SYMBOL_GPL(local_apic_timer_c2_ok);
@@ -896,6 +902,125 @@
 	apic_pm_activate();
 }
 
+void check_x2apic(void)
+{
+	int msr, msr2;
+
+	rdmsr(MSR_IA32_APICBASE, msr, msr2);
+
+	if (msr & X2APIC_ENABLE) {
+		printk("x2apic enabled by BIOS, switching to x2apic ops\n");
+		x2apic_preenabled = x2apic = 1;
+		apic_ops = &x2apic_ops;
+	}
+}
+
+void enable_x2apic(void)
+{
+	int msr, msr2;
+
+	rdmsr(MSR_IA32_APICBASE, msr, msr2);
+	if (!(msr & X2APIC_ENABLE)) {
+		printk("Enabling x2apic\n");
+		wrmsr(MSR_IA32_APICBASE, msr | X2APIC_ENABLE, 0);
+	}
+}
+
+void enable_IR_x2apic(void)
+{
+#ifdef CONFIG_INTR_REMAP
+	int ret;
+	unsigned long flags;
+
+	if (!cpu_has_x2apic)
+		return;
+
+	if (!x2apic_preenabled && disable_x2apic) {
+		printk(KERN_INFO
+		       "Skipped enabling x2apic and Interrupt-remapping "
+		       "because of nox2apic\n");
+		return;
+	}
+
+	if (x2apic_preenabled && disable_x2apic)
+		panic("Bios already enabled x2apic, can't enforce nox2apic");
+
+	if (!x2apic_preenabled && skip_ioapic_setup) {
+		printk(KERN_INFO
+		       "Skipped enabling x2apic and Interrupt-remapping "
+		       "because of skipping io-apic setup\n");
+		return;
+	}
+
+	ret = dmar_table_init();
+	if (ret) {
+		printk(KERN_INFO
+		       "dmar_table_init() failed with %d:\n", ret);
+
+		if (x2apic_preenabled)
+			panic("x2apic enabled by bios. But IR enabling failed");
+		else
+			printk(KERN_INFO
+			       "Not enabling x2apic,Intr-remapping\n");
+		return;
+	}
+
+	local_irq_save(flags);
+	mask_8259A();
+	save_mask_IO_APIC_setup();
+
+	ret = enable_intr_remapping(1);
+
+	if (ret && x2apic_preenabled) {
+		local_irq_restore(flags);
+		panic("x2apic enabled by bios. But IR enabling failed");
+	}
+
+	if (ret)
+		goto end;
+
+	if (!x2apic) {
+		x2apic = 1;
+		apic_ops = &x2apic_ops;
+		enable_x2apic();
+	}
+end:
+	if (ret)
+		/*
+		 * IR enabling failed
+		 */
+		restore_IO_APIC_setup();
+	else
+		reinit_intr_remapped_IO_APIC(x2apic_preenabled);
+
+	unmask_8259A();
+	local_irq_restore(flags);
+
+	if (!ret) {
+		if (!x2apic_preenabled)
+			printk(KERN_INFO
+			       "Enabled x2apic and interrupt-remapping\n");
+		else
+			printk(KERN_INFO
+			       "Enabled Interrupt-remapping\n");
+	} else
+		printk(KERN_ERR
+		       "Failed to enable Interrupt-remapping and x2apic\n");
+#else
+	if (!cpu_has_x2apic)
+		return;
+
+	if (x2apic_preenabled)
+		panic("x2apic enabled prior OS handover,"
+		      " enable CONFIG_INTR_REMAP");
+
+	printk(KERN_INFO "Enable CONFIG_INTR_REMAP for enabling intr-remapping "
+	       " and x2apic\n");
+#endif
+
+	return;
+}
+
 /*
  * Detect and enable local APICs on non-SMP boards.
  * Original code written by Keir Fraser.
@@ -943,6 +1068,11 @@
  */
 void __init init_apic_mappings(void)
 {
+	if (x2apic) {
+		boot_cpu_physical_apicid = GET_APIC_ID(read_apic_id());
+		return;
+	}
+
 	/*
 	 * If no local APIC can be found then set up a fake all
 	 * zeroes page to simulate the local APIC and another
@@ -981,6 +1111,9 @@
 		return -1;
 	}
 
+	enable_IR_x2apic();
+	setup_apic_routing();
+
 	verify_local_APIC();
 
 	connect_bsp_APIC();
@@ -1238,10 +1371,14 @@
 	maxlvt = lapic_get_maxlvt();
 
 	local_irq_save(flags);
-	rdmsr(MSR_IA32_APICBASE, l, h);
-	l &= ~MSR_IA32_APICBASE_BASE;
-	l |= MSR_IA32_APICBASE_ENABLE | mp_lapic_addr;
-	wrmsr(MSR_IA32_APICBASE, l, h);
+	if (!x2apic) {
+		rdmsr(MSR_IA32_APICBASE, l, h);
+		l &= ~MSR_IA32_APICBASE_BASE;
+		l |= MSR_IA32_APICBASE_ENABLE | mp_lapic_addr;
+		wrmsr(MSR_IA32_APICBASE, l, h);
+	} else
+		enable_x2apic();
+
 	apic_write(APIC_LVTERR, ERROR_APIC_VECTOR | APIC_LVT_MASKED);
 	apic_write(APIC_ID, apic_pm_state.apic_id);
 	apic_write(APIC_DFR, apic_pm_state.apic_dfr);
@@ -1381,6 +1518,15 @@
 	return (clusters > 2);
 }
 
+static __init int setup_nox2apic(char *str)
+{
+	disable_x2apic = 1;
+	clear_cpu_cap(&boot_cpu_data, X86_FEATURE_X2APIC);
+	return 0;
+}
+early_param("nox2apic", setup_nox2apic);
+
+
 /*
  * APIC command line parameters
  */
diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index 36537ab..e7bf3c2 100644
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -606,6 +606,8 @@
 	barrier();
 
 	check_efer();
+	if (cpu != 0 && x2apic)
+		enable_x2apic();
 
 	/*
 	 * set up and load the per-CPU TSS
diff --git a/arch/x86/kernel/genapic_64.c b/arch/x86/kernel/genapic_64.c
index 1029e17..792e21b 100644
--- a/arch/x86/kernel/genapic_64.c
+++ b/arch/x86/kernel/genapic_64.c
@@ -16,6 +16,7 @@
 #include <linux/ctype.h>
 #include <linux/init.h>
 #include <linux/hardirq.h>
+#include <linux/dmar.h>
 
 #include <asm/smp.h>
 #include <asm/ipi.h>
diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
index 3b25e49..70e1f3e 100644
--- a/arch/x86/kernel/mpparse.c
+++ b/arch/x86/kernel/mpparse.c
@@ -545,7 +545,9 @@
        generic_bigsmp_probe();
 #endif
 
+#ifdef CONFIG_X86_32
 	setup_apic_routing();
+#endif
 	if (!num_processors)
 		printk(KERN_ERR "MPTABLE: no processors registered!\n");
 	return num_processors;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 987b6fd..2e78a14 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -730,6 +730,8 @@
 	num_physpages = max_pfn;
 
 	check_efer();
+ 	if (cpu_has_x2apic)
+ 		check_x2apic();
 
 	/* How many end-of-memory variables you have, grandma! */
 	/* need this before calling reserve_initrd */
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c55263b..0c43e1f 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1145,6 +1145,11 @@
 	current_thread_info()->cpu = 0;  /* needed? */
 	set_cpu_sibling_map(0);
 
+#ifdef CONFIG_X86_64
+	enable_IR_x2apic();
+	setup_apic_routing();
+#endif
+
 	if (smp_sanity_check(max_cpus) < 0) {
 		printk(KERN_INFO "SMP disabled\n");
 		disable_smp();
diff --git a/include/asm-x86/apic.h b/include/asm-x86/apic.h
index aa74670..129752d 100644
--- a/include/asm-x86/apic.h
+++ b/include/asm-x86/apic.h
@@ -100,6 +100,11 @@
 extern u32 safe_apic_wait_icr_idle(void);
 extern void apic_icr_write(u32 low, u32 id);
 #else
+extern int x2apic, x2apic_preenabled;
+extern void check_x2apic(void);
+extern void enable_x2apic(void);
+extern void enable_IR_x2apic(void);
+extern void x2apic_icr_write(u32 low, u32 id);
 
 struct apic_ops {
 	u32 (*read)(u32 reg);