pseries: Use #define for XICS base irq number

Currently the lowest "real" irq number for the XICS irq controller (as
opposed to numbers reserved for IPIs and other special purposes) is
hard coded as 16 in two places - in xics_system_init() and in spapr.c.

As well as being generally bad practice, we're going to need to change this
number soon to fit in with the in-kernel XICS implementation.  This patch
adds a #define for this number to avoid future breakage.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NBen Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAlexander Graf <agraf@suse.de>

hw/spapr.c

@@ -801,7 +801,7 @@ static void ppc_spapr_init(QEMUMachineInitArgs *args)
 
     /* Set up Interrupt Controller */
     spapr->icp = xics_system_init(XICS_IRQS);
-    spapr->next_irq = 16;
+    spapr->next_irq = XICS_IRQ_BASE;
 
     /* Set up EPOW events infrastructure */
     spapr_events_init(spapr);

hw/xics.c

@@ -549,7 +549,7 @@ struct icp_state *xics_system_init(int nr_irqs)
 
     ics = g_malloc0(sizeof(*ics));
     ics->nr_irqs = nr_irqs;
-    ics->offset = 16;
+    ics->offset = XICS_IRQ_BASE;
     ics->irqs = g_malloc0(nr_irqs * sizeof(struct ics_irq_state));
 
     icp->ics = ics;

hw/xics.h

@@ -28,6 +28,7 @@
 #define __XICS_H__
 
 #define XICS_IPI        0x2
+#define XICS_IRQ_BASE   0x10
 
 struct icp_state;