hw/misc/a9scu: Do not allow invalid CPU count

Per the datasheet (DDI0407 r2p0):

  "The SCU connects one to four Cortex-A9 processors to
   the memory system through the AXI interfaces."

Change the instance_init() handler to a device_realize()
one so we can verify the property is in range, and return
an error to the caller if not.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200901144100.116742-2-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 13 insertions, 5 deletions

diff --git a/hw/misc/a9scu.c b/hw/misc/a9scu.c
index 324371a..915f127 100644
--- a/hw/misc/a9scu.c
+++ b/hw/misc/a9scu.c
@@ -12,8 +12,11 @@
 #include "hw/misc/a9scu.h"
 #include "hw/qdev-properties.h"
 #include "migration/vmstate.h"
+#include "qapi/error.h"
 #include "qemu/module.h"
 
+#define A9_SCU_CPU_MAX  4
+
 static uint64_t a9_scu_read(void *opaque, hwaddr offset,
                             unsigned size)
 {
@@ -105,12 +108,17 @@ static void a9_scu_reset(DeviceState *dev)
     s->control = 0;
 }
 
-static void a9_scu_init(Object *obj)
+static void a9_scu_realize(DeviceState *dev, Error **errp)
 {
-    A9SCUState *s = A9_SCU(obj);
-    SysBusDevice *sbd = SYS_BUS_DEVICE(obj);
+    A9SCUState *s = A9_SCU(dev);
+    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
+
+    if (!s->num_cpu || s->num_cpu > A9_SCU_CPU_MAX) {
+        error_setg(errp, "Illegal CPU count: %u", s->num_cpu);
+        return;
+    }
 
-    memory_region_init_io(&s->iomem, obj, &a9_scu_ops, s,
+    memory_region_init_io(&s->iomem, OBJECT(s), &a9_scu_ops, s,
                           "a9-scu", 0x100);
     sysbus_init_mmio(sbd, &s->iomem);
 }
@@ -138,13 +146,13 @@ static void a9_scu_class_init(ObjectClass *klass, void *data)
     device_class_set_props(dc, a9_scu_properties);
     dc->vmsd = &vmstate_a9_scu;
     dc->reset = a9_scu_reset;
+    dc->realize = a9_scu_realize;
 }
 
 static const TypeInfo a9_scu_info = {
     .name          = TYPE_A9_SCU,
     .parent        = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(A9SCUState),
-    .instance_init = a9_scu_init,
     .class_init    = a9_scu_class_init,
 };