pci: don't hw_error() when no slot is available.

Current PCI code will simply hw_error() and thus abort in case no free
PCI slot is available or the requested PCI slot is already in use by
another device.  For the hotplug case this behavior is not acceptable.
This patch makes qemu pass up the error properly, so the calling code
can decide whenever it wants to exit with an error (on startup) or
whenever it wants to continue (hotplug).
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/pci.c

@@ -580,11 +580,13 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
             if (!bus->devices[devfn])
                 goto found;
         }
-        hw_error("PCI: no devfn available for %s, all in use\n", name);
+        qemu_error("PCI: no devfn available for %s, all in use\n", name);
+        return NULL;
     found: ;
     } else if (bus->devices[devfn]) {
-        hw_error("PCI: devfn %d not available for %s, in use by %s\n", devfn,
+        qemu_error("PCI: devfn %d not available for %s, in use by %s\n", devfn,
                  name, bus->devices[devfn]->name);
+        return NULL;
     }
     pci_dev->bus = bus;
     pci_dev->devfn = devfn;
@@ -625,6 +627,9 @@ PCIDevice *pci_register_device(PCIBus *bus, const char *name,
     pci_dev = do_pci_register_device(pci_dev, bus, name, devfn,
                                      config_read, config_write,
                                      PCI_HEADER_TYPE_NORMAL);
+    if (pci_dev == NULL) {
+        hw_error("PCI: can't register device\n");
+    }
     return pci_dev;
 }
 static target_phys_addr_t pci_to_cpu_addr(target_phys_addr_t addr)
@@ -1376,6 +1381,8 @@ static int pci_qdev_init(DeviceState *qdev, DeviceInfo *base)
     pci_dev = do_pci_register_device(pci_dev, bus, base->name, devfn,
                                      info->config_read, info->config_write,
                                      info->header_type);
+    if (pci_dev == NULL)
+        return -1;
     rc = info->init(pci_dev);
     if (rc != 0)
         return rc;