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>

include/hw/ppc/spapr_irq.h

@@ -0,0 +1,32 @@
+/*
+ * QEMU PowerPC sPAPR IRQ backend definitions
+ *
+ * Copyright (c) 2018, IBM Corporation.
+ *
+ * This code is licensed under the GPL version 2 or later. See the
+ * COPYING file in the top-level directory.
+ */
+
+#ifndef HW_SPAPR_IRQ_H
+#define HW_SPAPR_IRQ_H
+
+/*
+ * IRQ range offsets per device type
+ */
+#define SPAPR_IRQ_EPOW       0x1000  /* XICS_IRQ_BASE offset */
+#define SPAPR_IRQ_HOTPLUG    0x1001
+#define SPAPR_IRQ_VIO        0x1100  /* 256 VIO devices */
+#define SPAPR_IRQ_PCI_LSI    0x1200  /* 32+ PHBs devices */
+
+#define SPAPR_IRQ_MSI        0x1300  /* Offset of the dynamic range covered
+                                      * by the bitmap allocator */
+
+typedef struct sPAPRMachineState sPAPRMachineState;
+
+void spapr_irq_msi_init(sPAPRMachineState *spapr, uint32_t nr_msis);
+int spapr_irq_msi_alloc(sPAPRMachineState *spapr, uint32_t num, bool align,
+                        Error **errp);
+void spapr_irq_msi_free(sPAPRMachineState *spapr, int irq, uint32_t num);
+void spapr_irq_msi_reset(sPAPRMachineState *spapr);
+
+#endif