x86/io_apic: add get_nr_irqs_gsi()

Impact: new interface to get max GSI

Add get_nr_irqs_gsi() to return nr_irqs_gsi.  Xen will use this to
determine how many irqs it needs to reserve for hardware irqs.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: N"H. Peter Anvin" <hpa@zytor.com>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>

arch/x86/include/asm/io_apic.h

@@ -169,6 +169,7 @@ extern void mask_IO_APIC_setup(struct IO_APIC_route_entry **ioapic_entries);
 extern int restore_IO_APIC_setup(struct IO_APIC_route_entry **ioapic_entries);
 
 extern void probe_nr_irqs_gsi(void);
+extern int get_nr_irqs_gsi(void);
 
 extern void setup_ioapic_ids_from_mpc(void);
 

arch/x86/kernel/apic/io_apic.c

@@ -3649,6 +3649,11 @@ void __init probe_nr_irqs_gsi(void)
 	printk(KERN_DEBUG "nr_irqs_gsi: %d\n", nr_irqs_gsi);
 }
 
+int get_nr_irqs_gsi(void)
+{
+	return nr_irqs_gsi;
+}
+
 #ifdef CONFIG_SPARSE_IRQ
 int __init arch_probe_nr_irqs(void)
 {