x86: fix off-by-one in nr_irqs_gsi calculation

highest_gsi() returns the last valid GSI, not a count.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Joe Jin <joe.jin@oracle.com>
Acked-by: Keir Fraser <keir@xen.org>
xen-unstable changeset:   25688:e6266fc76d08
xen-unstable date:        Fri Jul 27 12:22:13 2012 +0200

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index ea627672afb6df3242beb70a698f3ba6cbce5b19..842e4cf21dbe4a4744b151258e6a8482c02e753c 100644 (file)
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2589,7 +2589,7 @@ void __init init_ioapic_mappings(void)
         }
     }
 
-    nr_irqs_gsi = max(nr_irqs_gsi, highest_gsi());
+    nr_irqs_gsi = max(nr_irqs_gsi, highest_gsi() + 1);
 
     if ( !smp_found_config || skip_ioapic_setup || nr_irqs_gsi < 16 )
         nr_irqs_gsi = 16;