diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index d22f732eab8f6c43310985ebeeaec6219b9e4e04..8c5620147c4005ba243f7bb6c736d5d0eaf4f792 100644
--- a/arch/x86/include/asm/mpspec.h
+++ b/arch/x86/include/asm/mpspec.h
@@ -73,6 +73,7 @@ extern void mp_override_legacy_irq(u8 bus_irq, u8 polarity, u8 trigger,
 				   u32 gsi);
 extern void mp_config_acpi_legacy_irqs(void);
 extern int mp_register_gsi(u32 gsi, int edge_level, int active_high_low);
+extern int acpi_probe_gsi(void);
 #ifdef CONFIG_X86_IO_APIC
 extern int mp_config_acpi_gsi(unsigned char number, unsigned int devfn, u8 pin,
 				u32 gsi, int triggering, int polarity);
@@ -84,6 +85,11 @@ mp_config_acpi_gsi(unsigned char number, unsigned int devfn, u8 pin,
 	return 0;
 }
 #endif
+#else /* !CONFIG_ACPI: */
+static inline int acpi_probe_gsi(void)
+{
+	return 0;
+}
 #endif /* CONFIG_ACPI */
 
 #define PHYSID_ARRAY_SIZE	BITS_TO_LONGS(MAX_APICS)
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 3efa996b036c005168e90dae302ad420e0247027..c334fe75dcd63f90e042ca8aa871bd77d93e93d0 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -961,6 +961,29 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base)
 	nr_ioapics++;
 }
 
+int __init acpi_probe_gsi(void)
+{
+	int idx;
+	int gsi;
+	int max_gsi = 0;
+
+	if (acpi_disabled)
+		return 0;
+
+	if (!acpi_ioapic)
+		return 0;
+
+	max_gsi = 0;
+	for (idx = 0; idx < nr_ioapics; idx++) {
+		gsi = mp_ioapic_routing[idx].gsi_end;
+
+		if (gsi > max_gsi)
+			max_gsi = gsi;
+	}
+
+	return max_gsi + 1;
+}
+
 static void assign_to_mp_irq(struct mpc_intsrc *m,
 				    struct mpc_intsrc *mp_irq)
 {
diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index 855209a1b172273b04d105584dffe9512699a778..56e51eb551a500f80541ae84d368bd83c4d59d51 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -3824,14 +3824,24 @@ int __init io_apic_get_redir_entries (int ioapic)
 
 void __init probe_nr_irqs_gsi(void)
 {
-	int idx;
 	int nr = 0;
 
-	for (idx = 0; idx < nr_ioapics; idx++)
-		nr += io_apic_get_redir_entries(idx) + 1;
-
-	if (nr > nr_irqs_gsi)
+	nr = acpi_probe_gsi();
+	if (nr > nr_irqs_gsi) {
 		nr_irqs_gsi = nr;
+	} else {
+		/* for acpi=off or acpi is not compiled in */
+		int idx;
+
+		nr = 0;
+		for (idx = 0; idx < nr_ioapics; idx++)
+			nr += io_apic_get_redir_entries(idx) + 1;
+
+		if (nr > nr_irqs_gsi)
+			nr_irqs_gsi = nr;
+	}
+
+	printk(KERN_DEBUG "nr_irqs_gsi: %d\n", nr_irqs_gsi);
 }
 
 #ifdef CONFIG_SPARSE_IRQ