hw/i386/pc: support '-nic' for xen-net-device

The default NIC creation seems a bit hackish to me. I don't understand
why each platform has to call pci_nic_init_nofail() from a point in the
code where it actually has a pointer to the PCI bus, and then we have
the special cases for things like ne2k_isa.

If qmp_device_add() can *find* the appropriate bus and instantiate
the device on it, why can't we just do that from generic code for
creating the default NICs too?

But that isn't a yak I want to shave today. Add a xenbus field to the
PCMachineState so that it can make its way from pc_basic_device_init()
to pc_nic_init() and be handled as a special case like ne2k_isa is.

Now we can launch emulated Xen guests with '-nic user'.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

hw/i386/pc.c

@@ -1261,7 +1261,7 @@ void pc_basic_device_init(struct PCMachineState *pcms,
         if (pcms->bus) {
             pci_create_simple(pcms->bus, -1, "xen-platform");
         }
-        xen_bus_init();
+        pcms->xenbus = xen_bus_init();
         xen_be_init();
     }
 #endif
@@ -1289,7 +1289,8 @@ void pc_basic_device_init(struct PCMachineState *pcms,
                     pcms->vmport != ON_OFF_AUTO_ON);
 }
 
-void pc_nic_init(PCMachineClass *pcmc, ISABus *isa_bus, PCIBus *pci_bus)
+void pc_nic_init(PCMachineClass *pcmc, ISABus *isa_bus, PCIBus *pci_bus,
+                 BusState *xen_bus)
 {
     MachineClass *mc = MACHINE_CLASS(pcmc);
     int i;
@@ -1299,7 +1300,11 @@ void pc_nic_init(PCMachineClass *pcmc, ISABus *isa_bus, PCIBus *pci_bus)
         NICInfo *nd = &nd_table[i];
         const char *model = nd->model ? nd->model : mc->default_nic;
 
-        if (g_str_equal(model, "ne2k_isa")) {
+        if (xen_bus && (!nd->model || g_str_equal(model, "xen-net-device"))) {
+            DeviceState *dev = qdev_new("xen-net-device");
+            qdev_set_nic_properties(dev, nd);
+            qdev_realize_and_unref(dev, xen_bus, &error_fatal);
+        } else if (g_str_equal(model, "ne2k_isa")) {
             pc_init_ne2k_isa(isa_bus, nd);
         } else {
             pci_nic_init_nofail(nd, pci_bus, model, NULL);

hw/i386/pc_piix.c

@@ -342,7 +342,7 @@ static void pc_init1(MachineState *machine,
     pc_basic_device_init(pcms, isa_bus, x86ms->gsi, rtc_state, true,
                          0x4);
 
-    pc_nic_init(pcmc, isa_bus, pci_bus);
+    pc_nic_init(pcmc, isa_bus, pci_bus, pcms->xenbus);
 
     if (pcmc->pci_enabled) {
         pc_cmos_init(pcms, idebus[0], idebus[1], rtc_state);

hw/i386/pc_q35.c

@@ -340,7 +340,7 @@ static void pc_q35_init(MachineState *machine)
 
     /* the rest devices to which pci devfn is automatically assigned */
     pc_vga_init(isa_bus, host_bus);
-    pc_nic_init(pcmc, isa_bus, host_bus);
+    pc_nic_init(pcmc, isa_bus, host_bus, pcms->xenbus);
 
     if (machine->nvdimms_state->is_enabled) {
         nvdimm_init_acpi_state(machine->nvdimms_state, system_io,

hw/xen/xen-bus.c

@@ -1133,11 +1133,13 @@ static void xen_register_types(void)
 
 type_init(xen_register_types)
 
-void xen_bus_init(void)
+BusState *xen_bus_init(void)
 {
     DeviceState *dev = qdev_new(TYPE_XEN_BRIDGE);
     BusState *bus = qbus_new(TYPE_XEN_BUS, dev, NULL);
 
     sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
     qbus_set_bus_hotplug_handler(bus);
+
+    return bus;
 }

include/hw/i386/pc.h

@@ -33,6 +33,7 @@ typedef struct PCMachineState {
 
     /* Pointers to devices and objects: */
     PCIBus *bus;
+    BusState *xenbus;
     I2CBus *smbus;
     PFlashCFI01 *flash[2];
     ISADevice *pcspk;
@@ -184,7 +185,8 @@ void pc_basic_device_init(struct PCMachineState *pcms,
 void pc_cmos_init(PCMachineState *pcms,
                   BusState *ide0, BusState *ide1,
                   ISADevice *s);
-void pc_nic_init(PCMachineClass *pcmc, ISABus *isa_bus, PCIBus *pci_bus);
+void pc_nic_init(PCMachineClass *pcmc, ISABus *isa_bus, PCIBus *pci_bus,
+                 BusState *xen_bus);
 
 void pc_i8259_create(ISABus *isa_bus, qemu_irq *i8259_irqs);
 

include/hw/xen/xen-bus.h

@@ -75,7 +75,7 @@ struct XenBusClass {
 OBJECT_DECLARE_TYPE(XenBus, XenBusClass,
                     XEN_BUS)
 
-void xen_bus_init(void);
+BusState *xen_bus_init(void);
 
 void xen_device_backend_set_state(XenDevice *xendev,
                                   enum xenbus_state state);