pci address conflict when virtio disk with drive type

When using the xml as below:
------------------------------------------------------
<devices>
  <emulator>/home/soulxu/data/work-code/qemu-kvm/x86_64-softmmu/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
    <driver name='qemu' type='qcow2'/>
    <source file='/home/soulxu/data/VM/images/linux.img'/>
    <target dev='vda' bus='virtio'/>
    <address type='drive' controller='0' bus='0' unit='0'/>
  </disk>
  <input type='mouse' bus='ps2'/>
  <graphics type='vnc' port='-1' autoport='yes'/>
  <video>
    <model type='cirrus' vram='9216' heads='1'/>
    <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
  </video>
  <memballoon model='virtio'>
    <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
  </memballoon>
</devices>
------------------------------------------------------

Then can't startup qemu, the error message as below:
virsh # start test-vm
error: Failed to start domain test-vm
error: internal error process exited while connecting to monitor: qemu-system-x86_64: -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3: PCI: slot 3 function 0 not available for virtio-balloon-pci, in use by virtio-blk-pci
qemu-system-x86_64: -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3: Device 'virtio-balloon-pci' could not be initialized

So adding check for bus type and address type. Only the address of pci type support by virtio bus.
Signed-off-by: NXu He Jie <xuhj@linux.vnet.ibm.com>

src/qemu/qemu_command.c

@@ -1319,15 +1319,21 @@ qemuAssignDevicePCISlots(virDomainDefPtr def, qemuDomainPCIAddressSetPtr addrs)
             goto error;
     }
 
-    /* Disks (VirtIO only for now */
+    /* Disks (VirtIO only for now) */
     for (i = 0; i < def->ndisks ; i++) {
-        if (def->disks[i]->info.type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE)
-            continue;
-
         /* Only VirtIO disks use PCI addrs */
         if (def->disks[i]->bus != VIR_DOMAIN_DISK_BUS_VIRTIO)
             continue;
 
+        if (def->disks[i]->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI)
+            continue;
+
+        if (def->disks[i]->info.type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE) {
+            qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                          _("virtio only support device address type 'PCI'"));
+            goto error;
+        }
+
         if (qemuDomainPCIAddressSetNextAddr(addrs, &def->disks[i]->info) < 0)
             goto error;
     }