3 files changed, 44 insertions, 5 deletions

diff --git a/arch/x86/include/asm/mpspec.h b/arch/x86/include/asm/mpspec.h
index 62d14ce3cd00..bd22f2a3713f 100644
--- a/arch/x86/include/asm/mpspec.h
+++ b/arch/x86/include/asm/mpspec.h
@@ -60,6 +60,7 @@ 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);
@@ -71,6 +72,11 @@ 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 d37593c2f438..7678f10c4568 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -973,6 +973,29 @@ 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 mp_config_intsrc *m,
                                     struct mp_config_intsrc *mp_irq)
 {
diff --git a/arch/x86/kernel/io_apic.c b/arch/x86/kernel/io_apic.c
index 9b0c480c383b..bc7ac4da90d7 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -3841,14 +3841,24 @@ 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);
 }
 
 /* --------------------------------------------------------------------------