hw/i386/pc: Use machine_memory_devices_init()

Let's use our new helper and stop always allocating ms->device_memory.
Once allcoated, we're sure that the size > 0 and that the base was
initialized.

Adjust the code in pc_memory_init() to check for machine->device_memory
instead of pcmc->has_reserved_memory and machine->device_memory->base.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Eduardo Habkost <eduardo@habkost.net>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20230623124553.400585-7-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

hw/i386/pc.c

@@ -1039,13 +1039,11 @@ void pc_memory_init(PCMachineState *pcms,
         exit(EXIT_FAILURE);
     }
 
-    /* always allocate the device memory information */
-    machine->device_memory = g_malloc0(sizeof(*machine->device_memory));
-
     /* initialize device memory address space */
     if (pcmc->has_reserved_memory &&
         (machine->ram_size < machine->maxram_size)) {
         ram_addr_t device_mem_size;
+        hwaddr device_mem_base;
 
         if (machine->ram_slots > ACPI_MAX_RAM_SLOTS) {
             error_report("unsupported amount of memory slots: %"PRIu64,
@@ -1060,19 +1058,14 @@ void pc_memory_init(PCMachineState *pcms,
             exit(EXIT_FAILURE);
         }
 
-        pc_get_device_memory_range(pcms, &machine->device_memory->base, &device_mem_size);
+        pc_get_device_memory_range(pcms, &device_mem_base, &device_mem_size);
 
-        if ((machine->device_memory->base + device_mem_size) <
-            device_mem_size) {
+        if (device_mem_base + device_mem_size < device_mem_size) {
             error_report("unsupported amount of maximum memory: " RAM_ADDR_FMT,
                          machine->maxram_size);
             exit(EXIT_FAILURE);
         }
-
-        memory_region_init(&machine->device_memory->mr, OBJECT(pcms),
-                           "device-memory", device_mem_size);
-        memory_region_add_subregion(system_memory, machine->device_memory->base,
-                                    &machine->device_memory->mr);
+        machine_memory_devices_init(machine, device_mem_base, device_mem_size);
     }
 
     if (pcms->cxl_devices_state.is_enabled) {
@@ -1120,7 +1113,7 @@ void pc_memory_init(PCMachineState *pcms,
 
     rom_set_fw(fw_cfg);
 
-    if (pcmc->has_reserved_memory && machine->device_memory->base) {
+    if (machine->device_memory) {
         uint64_t *val = g_malloc(sizeof(*val));
         PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
         uint64_t res_mem_end = machine->device_memory->base;