hw/mips: Use MachineClass->default_nic in the virt machine

Mark the default NIC via the new MachineClass->default_nic setting
so that the machine-defaults code in vl.c can decide whether the
default NIC is usable or not (for example when compiling with the
"--without-default-devices" configure switch).

Inspired-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230524122559.28863-1-philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/mips/loongson3_virt.c

@@ -406,6 +406,7 @@ static inline void loongson3_virt_devices_init(MachineState *machine,
     PCIBus *pci_bus;
     DeviceState *dev;
     MemoryRegion *mmio_reg, *ecam_reg;
+    MachineClass *mc = MACHINE_GET_CLASS(machine);
     LoongsonMachineState *s = LOONGSON_MACHINE(machine);
 
     dev = qdev_new(TYPE_GPEX_HOST);
@@ -456,7 +457,7 @@ static inline void loongson3_virt_devices_init(MachineState *machine,
         NICInfo *nd = &nd_table[i];
 
         if (!nd->model) {
-            nd->model = g_strdup("virtio");
+            nd->model = g_strdup(mc->default_nic);
         }
 
         pci_nic_init_nofail(nd, pci_bus, nd->model, NULL);
@@ -619,6 +620,7 @@ static void loongson3v_machine_class_init(ObjectClass *oc, void *data)
     mc->default_ram_size = 1600 * MiB;
     mc->kvm_type = mips_kvm_type;
     mc->minimum_page_bits = 14;
+    mc->default_nic = "virtio-net-pci";
 }
 
 static const TypeInfo loongson3_machine_types[] = {