diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index e5be9f35ea54..855209a1b172 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -1657,7 +1657,7 @@ static void __init setup_timer_IRQ0_pin(unsigned int apic_id, unsigned int pin,
 	 * to the first CPU.
 	 */
 	entry.dest_mode = apic->irq_dest_mode;
-	entry.mask = 1;					/* mask IRQ now */
+	entry.mask = 0;			/* don't mask IRQ for edge */
 	entry.dest = apic->cpu_mask_to_apicid(apic->target_cpus());
 	entry.delivery_mode = apic->irq_delivery_mode;
 	entry.polarity = 0;
@@ -2863,14 +2863,10 @@ static inline void __init check_timer(void)
 	int cpu = boot_cpu_id;
 	int apic1, pin1, apic2, pin2;
 	unsigned long flags;
-	unsigned int ver;
 	int no_pin1 = 0;
 
 	local_irq_save(flags);
 
-	ver = apic_read(APIC_LVR);
-	ver = GET_APIC_VERSION(ver);
-
 	/*
 	 * get/set the timer IRQ vector:
 	 */
@@ -2889,7 +2885,13 @@ static inline void __init check_timer(void)
 	apic_write(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
 	init_8259A(1);
 #ifdef CONFIG_X86_32
-	timer_ack = (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
+	{
+		unsigned int ver;
+
+		ver = apic_read(APIC_LVR);
+		ver = GET_APIC_VERSION(ver);
+		timer_ack = (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
+	}
 #endif
 
 	pin1  = find_isa_irq_pin(0, mp_INT);
@@ -2928,8 +2930,17 @@ static inline void __init check_timer(void)
 		if (no_pin1) {
 			add_pin_to_irq_cpu(cfg, cpu, apic1, pin1);
 			setup_timer_IRQ0_pin(apic1, pin1, cfg->vector);
+		} else {
+			/* for edge trigger, setup_IO_APIC_irq already
+			 * leave it unmasked.
+			 * so only need to unmask if it is level-trigger
+			 * do we really have level trigger timer?
+			 */
+			int idx;
+			idx = find_irq_entry(apic1, pin1, mp_INT);
+			if (idx != -1 && irq_trigger(idx))
+				unmask_IO_APIC_irq_desc(desc);
 		}
-		unmask_IO_APIC_irq_desc(desc);
 		if (timer_irq_works()) {
 			if (nmi_watchdog == NMI_IO_APIC) {
 				setup_nmi();
@@ -2943,6 +2954,7 @@ static inline void __init check_timer(void)
 		if (intr_remapping_enabled)
 			panic("timer doesn't work through Interrupt-remapped IO-APIC");
 #endif
+		local_irq_disable();
 		clear_IO_APIC_pin(apic1, pin1);
 		if (!no_pin1)
 			apic_printk(APIC_QUIET, KERN_ERR "..MP-BIOS bug: "
@@ -2957,7 +2969,6 @@ static inline void __init check_timer(void)
 		 */
 		replace_pin_at_irq_cpu(cfg, cpu, apic1, pin1, apic2, pin2);
 		setup_timer_IRQ0_pin(apic2, pin2, cfg->vector);
-		unmask_IO_APIC_irq_desc(desc);
 		enable_8259A_irq(0);
 		if (timer_irq_works()) {
 			apic_printk(APIC_QUIET, KERN_INFO "....... works.\n");
@@ -2972,6 +2983,7 @@ static inline void __init check_timer(void)
 		/*
 		 * Cleanup, just in case ...
 		 */
+		local_irq_disable();
 		disable_8259A_irq(0);
 		clear_IO_APIC_pin(apic2, pin2);
 		apic_printk(APIC_QUIET, KERN_INFO "....... failed.\n");
@@ -2997,6 +3009,7 @@ static inline void __init check_timer(void)
 		apic_printk(APIC_QUIET, KERN_INFO "..... works.\n");
 		goto out;
 	}
+	local_irq_disable();
 	disable_8259A_irq(0);
 	apic_write(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_FIXED | cfg->vector);
 	apic_printk(APIC_QUIET, KERN_INFO "..... failed.\n");
@@ -3014,6 +3027,7 @@ static inline void __init check_timer(void)
 		apic_printk(APIC_QUIET, KERN_INFO "..... works.\n");
 		goto out;
 	}
+	local_irq_disable();
 	apic_printk(APIC_QUIET, KERN_INFO "..... failed :(.\n");
 	panic("IO-APIC + timer doesn't work!  Boot with apic=debug and send a "
 		"report.  Then try booting with the 'noapic' option.\n");