hw/riscv: sifive_u: Use MachineState::ram and MachineClass::default_ram_id

Using memory_region_init_ram(), which can't possibly handle vhost-user,
and can't work as expected with '-numa node,memdev' options.

Use MachineState::ram instead of manually initializing RAM memory
region, as well as by providing MachineClass::default_ram_id to
opt in to memdev scheme.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20211020014112.7336-6-bmeng.cn@gmail.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/sifive_u.c

@@ -528,7 +528,6 @@ static void sifive_u_machine_init(MachineState *machine)
     const MemMapEntry *memmap = sifive_u_memmap;
     SiFiveUState *s = RISCV_U_MACHINE(machine);
     MemoryRegion *system_memory = get_system_memory();
-    MemoryRegion *main_mem = g_new(MemoryRegion, 1);
     MemoryRegion *flash0 = g_new(MemoryRegion, 1);
     target_ulong start_addr = memmap[SIFIVE_U_DEV_DRAM].base;
     target_ulong firmware_end_addr, kernel_start_addr;
@@ -549,10 +548,8 @@ static void sifive_u_machine_init(MachineState *machine)
     qdev_realize(DEVICE(&s->soc), NULL, &error_abort);
 
     /* register RAM */
-    memory_region_init_ram(main_mem, NULL, "riscv.sifive.u.ram",
-                           machine->ram_size, &error_fatal);
     memory_region_add_subregion(system_memory, memmap[SIFIVE_U_DEV_DRAM].base,
-                                main_mem);
+                                machine->ram);
 
     /* register QSPI0 Flash */
     memory_region_init_ram(flash0, NULL, "riscv.sifive.u.flash0",
@@ -748,6 +745,7 @@ static void sifive_u_machine_class_init(ObjectClass *oc, void *data)
     mc->min_cpus = SIFIVE_U_MANAGEMENT_CPU_COUNT + 1;
     mc->default_cpu_type = SIFIVE_U_CPU;
     mc->default_cpus = mc->min_cpus;
+    mc->default_ram_id = "riscv.sifive.u.ram";
 
     object_class_property_add_bool(oc, "start-in-flash",
                                    sifive_u_machine_get_start_in_flash,