memory-device: Introduce machine_memory_devices_init()

Let's intrduce a new helper that we will use to replace existing memory
device setup code during machine initialization. We'll enforce that the
size has to be > 0.

Once all machines were converted, we'll only allocate ms->device_memory
if the size > 0.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20230623124553.400585-3-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

hw/mem/memory-device.c

@@ -17,6 +17,7 @@
 #include "qemu/range.h"
 #include "hw/virtio/vhost.h"
 #include "sysemu/kvm.h"
+#include "exec/address-spaces.h"
 #include "trace.h"
 
 static gint memory_device_addr_sort(gconstpointer a, gconstpointer b)
@@ -328,6 +329,19 @@ uint64_t memory_device_get_region_size(const MemoryDeviceState *md,
     return memory_region_size(mr);
 }
 
+void machine_memory_devices_init(MachineState *ms, hwaddr base, uint64_t size)
+{
+    g_assert(size);
+    g_assert(!ms->device_memory);
+    ms->device_memory = g_new0(DeviceMemoryState, 1);
+    ms->device_memory->base = base;
+
+    memory_region_init(&ms->device_memory->mr, OBJECT(ms), "device-memory",
+                       size);
+    memory_region_add_subregion(get_system_memory(), ms->device_memory->base,
+                                &ms->device_memory->mr);
+}
+
 static const TypeInfo memory_device_info = {
     .name          = TYPE_MEMORY_DEVICE,
     .parent        = TYPE_INTERFACE,

include/hw/boards.h

@@ -37,6 +37,7 @@ void machine_parse_smp_config(MachineState *ms,
                               const SMPConfiguration *config, Error **errp);
 unsigned int machine_topo_get_cores_per_socket(const MachineState *ms);
 unsigned int machine_topo_get_threads_per_socket(const MachineState *ms);
+void machine_memory_devices_init(MachineState *ms, hwaddr base, uint64_t size);
 
 /**
  * machine_class_allow_dynamic_sysbus_dev: Add type to list of valid devices