spapr: introduce a fixed IRQ number space

This proposal introduces a new IRQ number space layout using static
numbers for all devices, depending on a device index, and a bitmap
allocator for the MSI IRQ numbers which are negotiated by the guest at
runtime.

As the VIO device model does not have a device index but a "reg"
property, we introduce a formula to compute an IRQ number from a "reg"
value. It should minimize most of the collisions.

The previous layout is kept in pre-3.1 machines raising the
'legacy_irq_allocation' machine class flag.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 8 insertions, 4 deletions

diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
index e4f5946..32719a1 100644
--- a/hw/ppc/spapr_events.c
+++ b/hw/ppc/spapr_events.c
@@ -707,9 +707,11 @@ void spapr_clear_pending_events(sPAPRMachineState *spapr)
 
 void spapr_events_init(sPAPRMachineState *spapr)
 {
-    int epow_irq;
+    int epow_irq = SPAPR_IRQ_EPOW;
 
-    epow_irq = spapr_irq_findone(spapr, &error_fatal);
+    if (SPAPR_MACHINE_GET_CLASS(spapr)->legacy_irq_allocation) {
+        epow_irq = spapr_irq_findone(spapr, &error_fatal);
+    }
 
     spapr_irq_claim(spapr, epow_irq, false, &error_fatal);
 
@@ -729,9 +731,11 @@ void spapr_events_init(sPAPRMachineState *spapr)
      * checking that it's enabled.
      */
     if (spapr->use_hotplug_event_source) {
-        int hp_irq;
+        int hp_irq = SPAPR_IRQ_HOTPLUG;
 
-        hp_irq = spapr_irq_findone(spapr, &error_fatal);
+        if (SPAPR_MACHINE_GET_CLASS(spapr)->legacy_irq_allocation) {
+            hp_irq = spapr_irq_findone(spapr, &error_fatal);
+        }
 
         spapr_irq_claim(spapr, hp_irq, false, &error_fatal);