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>

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index d213f2c388ed28a72430bcddba560b7e18accb8b..85191e0af2946957c079b296625368a587c52d32 100644 (file)
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2531,7 +2531,7 @@ 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 ( max_gsi_irqs == 0 )
         max_gsi_irqs = nr_irqs ? nr_irqs / 8 : PAGE_SIZE;