diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 4788b3f50f69..0592c38d9952 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -100,17 +100,6 @@ static u32 isa_irq_to_gsi[NR_IRQS_LEGACY] __read_mostly = {
 
 #define	ACPI_INVALID_GSI		INT_MIN
 
-static int map_gsi_to_irq(unsigned int gsi, unsigned int flags)
-{
-	int i;
-
-	for (i = 0; i < NR_IRQS_LEGACY; i++)
-		if (isa_irq_to_gsi[i] == gsi)
-			return i;
-
-	return mp_map_gsi_to_irq(gsi, flags);
-}
-
 /*
  * This is just a simple wrapper around early_ioremap(),
  * with sanity checks for phys == 0 and size == 0.
@@ -504,7 +493,7 @@ void __init acpi_pic_sci_set_trigger(unsigned int irq, u16 trigger)
 
 int acpi_gsi_to_irq(u32 gsi, unsigned int *irqp)
 {
-	int irq = map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
+	int irq = mp_map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC | IOAPIC_MAP_CHECK);
 
 	if (irq >= 0) {
 		*irqp = irq;
@@ -1051,7 +1040,7 @@ static int mp_register_gsi(struct device *dev, u32 gsi, int trigger,
 		return -1;
 	}
 
-	irq = map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC);
+	irq = mp_map_gsi_to_irq(gsi, IOAPIC_MAP_ALLOC);
 	if (irq < 0)
 		return irq;
 
diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 25a2877a5788..7fc34fcf3ea3 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -207,9 +207,6 @@ static int __init parse_noapic(char *str)
 }
 early_param("noapic", parse_noapic);
 
-static int io_apic_setup_irq_pin(unsigned int irq, int node,
-				 struct io_apic_irq_attr *attr);
-
 /* Will be called in mpparse/acpi/sfi codes for saving IRQ info */
 void mp_save_irq(struct mpc_intsrc *m)
 {
@@ -1021,34 +1018,35 @@ static int mp_map_pin_to_irq(u32 gsi, int idx, int ioapic, int pin,
 	struct irq_domain *domain = mp_ioapic_irqdomain(ioapic);
 	struct mp_pin_info *info = mp_pin_info(ioapic, pin);
 
+	if (!domain)
+		return -1;
+
+	mutex_lock(&ioapic_mutex);
+
 	/*
 	 * Don't use irqdomain to manage ISA IRQs because there may be
 	 * multiple IOAPIC pins sharing the same ISA IRQ number and
 	 * irqdomain only supports 1:1 mapping between IOAPIC pin and
 	 * IRQ number.
 	 */
-	if (idx >= 0 && test_bit(mp_irqs[idx].srcbus, mp_bus_not_pci))
-		return mp_irqs[idx].srcbusirq;
-
-	if (!domain) {
-		/*
-		 * Provide an identity mapping of gsi == irq except on truly
-		 * weird platforms that have non isa irqs in the first 16 gsis.
-		 */
-		return gsi >= NR_IRQS_LEGACY ? gsi : gsi_top + gsi;
+	if (idx >= 0 && test_bit(mp_irqs[idx].srcbus, mp_bus_not_pci)) {
+		irq = mp_irqs[idx].srcbusirq;
+		if ((flags & IOAPIC_MAP_ALLOC) && info->count == 0 &&
+		    mp_irqdomain_map(domain, irq, pin) != 0)
+			irq = -1;
+	} else {
+		irq = irq_find_mapping(domain, pin);
+		if (irq <= 0 && (flags & IOAPIC_MAP_ALLOC))
+			irq = alloc_irq_from_domain(domain, gsi, pin);
 	}
 
-	mutex_lock(&ioapic_mutex);
-	irq = irq_find_mapping(domain, pin);
-	if (irq <= 0 && (flags & IOAPIC_MAP_ALLOC))
-		irq = alloc_irq_from_domain(domain, gsi, pin);
-
 	if (flags & IOAPIC_MAP_ALLOC) {
 		if (irq > 0)
 			info->count++;
 		else if (info->count == 0)
 			info->set = 0;
 	}
+
 	mutex_unlock(&ioapic_mutex);
 
 	return irq > 0 ? irq : -1;
@@ -1465,55 +1463,23 @@ static void setup_ioapic_irq(unsigned int irq, struct irq_cfg *cfg,
 	ioapic_write_entry(attr->ioapic, attr->ioapic_pin, entry);
 }
 
-static bool __init io_apic_pin_not_connected(int idx, int ioapic_idx, int pin)
-{
-	if (idx != -1)
-		return false;
-
-	apic_printk(APIC_VERBOSE, KERN_DEBUG " apic %d pin %d not connected\n",
-		    mpc_ioapic_id(ioapic_idx), pin);
-	return true;
-}
-
-static void __init __io_apic_setup_irqs(unsigned int ioapic_idx)
-{
-	int idx, node = cpu_to_node(0);
-	struct io_apic_irq_attr attr;
-	unsigned int pin, irq;
-
-	for_each_pin(ioapic_idx, pin) {
-		idx = find_irq_entry(ioapic_idx, pin, mp_INT);
-		if (io_apic_pin_not_connected(idx, ioapic_idx, pin))
-			continue;
-
-		irq = pin_2_irq(idx, ioapic_idx, pin,
-				ioapic_idx ? 0 : IOAPIC_MAP_ALLOC);
-		if (irq < 0 || !mp_init_irq_at_boot(ioapic_idx, irq))
-			continue;
-
-		/*
-		 * Skip the timer IRQ if there's a quirk handler
-		 * installed and if it returns 1:
-		 */
-		if (apic->multi_timer_check &&
-		    apic->multi_timer_check(ioapic_idx, irq))
-			continue;
-
-		set_io_apic_irq_attr(&attr, ioapic_idx, pin, irq_trigger(idx),
-				     irq_polarity(idx));
-
-		io_apic_setup_irq_pin(irq, node, &attr);
-	}
-}
-
 static void __init setup_IO_APIC_irqs(void)
 {
-	unsigned int ioapic_idx;
+	unsigned int ioapic, pin;
+	int idx;
 
 	apic_printk(APIC_VERBOSE, KERN_DEBUG "init IO_APIC IRQs\n");
 
-	for_each_ioapic(ioapic_idx)
-		__io_apic_setup_irqs(ioapic_idx);
+	for_each_ioapic_pin(ioapic, pin) {
+		idx = find_irq_entry(ioapic, pin, mp_INT);
+		if (idx < 0)
+			apic_printk(APIC_VERBOSE,
+				    KERN_DEBUG " apic %d pin %d not connected\n",
+				    mpc_ioapic_id(ioapic), pin);
+		else
+			pin_2_irq(idx, ioapic, pin,
+				  ioapic ? 0 : IOAPIC_MAP_ALLOC);
+	}
 }
 
 /*
