1 files changed, 7 insertions, 3 deletions

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 73ec92838d83..0a053e61b3ea 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3855,7 +3855,11 @@ int __init io_apic_get_redir_entries (int ioapic)
         reg_01.raw = io_apic_read(ioapic, 1);
         raw_spin_unlock_irqrestore(&ioapic_lock, flags);
 
-        return reg_01.bits.entries;
+        /* The register returns the maximum index redir index
+         * supported, which is one less than the total number of redir
+         * entries.
+         */
+        return reg_01.bits.entries + 1;
 }
 
 void __init probe_nr_irqs_gsi(void)
@@ -3871,7 +3875,7 @@ void __init probe_nr_irqs_gsi(void)
 
                 nr = 0;
                 for (idx = 0; idx < nr_ioapics; idx++)
-                        nr += io_apic_get_redir_entries(idx) + 1;
+                        nr += io_apic_get_redir_entries(idx);
 
                 if (nr > nr_irqs_gsi)
                         nr_irqs_gsi = nr;
@@ -4306,7 +4310,7 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base)
          */
         mp_gsi_routing[idx].gsi_base = gsi_base;
         mp_gsi_routing[idx].gsi_end = gsi_base +
-            io_apic_get_redir_entries(idx);
+            io_apic_get_redir_entries(idx) - 1;
 
         printk(KERN_INFO "IOAPIC[%d]: apic_id %d, version %d, address 0x%x, "
                "GSI %d-%d\n", idx, mp_ioapics[idx].apicid,