ppc/spapr: use memdev for RAM

memory_region_allocate_system_memory() API is going away, so
replace it with memdev allocated MemoryRegion. The later is
initialized by generic code, so board only needs to opt in
to memdev scheme by providing
  MachineClass::default_ram_id
and using MachineState::ram instead of manually initializing
RAM memory region.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200219160953.13771-68-imammedo@redhat.com>

hw/ppc/spapr.c

@@ -2634,7 +2634,6 @@ static void spapr_machine_init(MachineState *machine)
     PCIHostState *phb;
     int i;
     MemoryRegion *sysmem = get_system_memory();
-    MemoryRegion *ram = g_new(MemoryRegion, 1);
     hwaddr node0_size = spapr_node0_size(machine);
     long load_limit, fw_size;
     char *filename;
@@ -2813,10 +2812,8 @@ static void spapr_machine_init(MachineState *machine)
         kvmppc_enable_h_page_init();
     }
 
-    /* allocate RAM */
-    memory_region_allocate_system_memory(ram, NULL, "ppc_spapr.ram",
-                                         machine->ram_size);
-    memory_region_add_subregion(sysmem, 0, ram);
+    /* map RAM */
+    memory_region_add_subregion(sysmem, 0, machine->ram);
 
     /* always allocate the device memory information */
     machine->device_memory = g_malloc0(sizeof(*machine->device_memory));
@@ -4400,6 +4397,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     mc->no_parallel = 1;
     mc->default_boot_order = "";
     mc->default_ram_size = 512 * MiB;
+    mc->default_ram_id = "ppc_spapr.ram";
     mc->default_display = "std";
     mc->kvm_type = spapr_kvm_type;
     machine_class_allow_dynamic_sysbus_dev(mc, TYPE_SPAPR_PCI_HOST_BRIDGE);