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, 56 insertions, 0 deletions

diff --git a/hw/ppc/spapr_irq.c b/hw/ppc/spapr_irq.c
new file mode 100644
index 0000000..24e9c1d
--- /dev/null
+++ b/hw/ppc/spapr_irq.c
@@ -0,0 +1,56 @@
+/*
+ * QEMU PowerPC sPAPR IRQ interface
+ *
+ * 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.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
+#include "hw/ppc/spapr.h"
+#include "hw/ppc/xics.h"
+
+void spapr_irq_msi_init(sPAPRMachineState *spapr, uint32_t nr_msis)
+{
+    spapr->irq_map_nr = nr_msis;
+    spapr->irq_map = bitmap_new(spapr->irq_map_nr);
+}
+
+int spapr_irq_msi_alloc(sPAPRMachineState *spapr, uint32_t num, bool align,
+                        Error **errp)
+{
+    int irq;
+
+    /*
+     * The 'align_mask' parameter of bitmap_find_next_zero_area()
+     * should be one less than a power of 2; 0 means no
+     * alignment. Adapt the 'align' value of the former allocator
+     * to fit the requirements of bitmap_find_next_zero_area()
+     */
+    align -= 1;
+
+    irq = bitmap_find_next_zero_area(spapr->irq_map, spapr->irq_map_nr, 0, num,
+                                     align);
+    if (irq == spapr->irq_map_nr) {
+        error_setg(errp, "can't find a free %d-IRQ block", num);
+        return -1;
+    }
+
+    bitmap_set(spapr->irq_map, irq, num);
+
+    return irq + SPAPR_IRQ_MSI;
+}
+
+void spapr_irq_msi_free(sPAPRMachineState *spapr, int irq, uint32_t num)
+{
+    bitmap_clear(spapr->irq_map, irq - SPAPR_IRQ_MSI, num);
+}
+
+void spapr_irq_msi_reset(sPAPRMachineState *spapr)
+{
+    bitmap_clear(spapr->irq_map, 0, spapr->irq_map_nr);
+}