[IA64] vector sharing (Large I/O system support)

Current ia64 linux cannot handle greater than 184 interrupt sources
because of the lack of vectors. The following patch enables ia64 linux
to handle greater than 184 interrupt sources by allowing the same
vector number to be shared by multiple IOSAPIC's RTEs. The design of
this patch is besed on "Intel(R) Itanium(R) Processor Family Interrupt
Architecture Guide".

Even if you don't have a large I/O system, you can see the behavior of
vector sharing by changing IOSAPIC_LAST_DEVICE_VECTOR to fewer value.
Signed-off-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/irq_ia64.c

@@ -63,20 +63,30 @@ EXPORT_SYMBOL(isa_irq_to_vector_map);
 static unsigned long ia64_vector_mask[BITS_TO_LONGS(IA64_NUM_DEVICE_VECTORS)];
 
 int
-assign_irq_vector (int irq)
+assign_irq_vector_nopanic (int irq)
 {
 	int pos, vector;
  again:
 	pos = find_first_zero_bit(ia64_vector_mask, IA64_NUM_DEVICE_VECTORS);
 	vector = IA64_FIRST_DEVICE_VECTOR + pos;
 	if (vector > IA64_LAST_DEVICE_VECTOR)
-		/* XXX could look for sharable vectors instead of panic'ing... */
-		panic("assign_irq_vector: out of interrupt vectors!");
+		return -1;
 	if (test_and_set_bit(pos, ia64_vector_mask))
 		goto again;
 	return vector;
 }
 
+int
+assign_irq_vector (int irq)
+{
+	int vector = assign_irq_vector_nopanic(irq);
+
+	if (vector < 0)
+		panic("assign_irq_vector: out of interrupt vectors!");
+
+	return vector;
+}
+
 void
 free_irq_vector (int vector)
 {

include/asm-ia64/hw_irq.h

@@ -81,6 +81,7 @@ extern __u8 isa_irq_to_vector_map[16];
 
 extern struct hw_interrupt_type irq_type_ia64_lsapic;	/* CPU-internal interrupt controller */
 
+extern int assign_irq_vector_nopanic (int irq); /* allocate a free vector without panic */
 extern int assign_irq_vector (int irq);	/* allocate a free vector */
 extern void free_irq_vector (int vector);
 extern void ia64_send_ipi (int cpu, int vector, int delivery_mode, int redirect);