2 files changed, 38 insertions, 5 deletions

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 3efa996b036c..c334fe75dcd6 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 855209a1b172..56e51eb551a5 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