qemu: reorganize loop in qemuDomainAssignPCIAddresses

This loop occurs just after we've assured that all devices that
require a PCI device have been assigned and all necessary PCI
controllers have been added. It is the perfect place to add other
potentially auto-generated PCI controller attributes that are
dependent on the controller's PCI address (upcoming patch).

There is a convenient loop through all controllers at the end of the
function, but the patch to add new functionality will be cleaner if we
first rearrange that loop a bit.

Note that the loop originally was accessing info.addr.pci.bus prior to
determining that the pci part of the object was valid. This isn't
dangerous in any way, but seemed a bit ugly, so I fixed it.

src/qemu/qemu_command.c

@@ -2248,20 +2248,24 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
                 goto cleanup;
 
             for (i = 0; i < def->ncontrollers; i++) {
+                virDomainControllerDefPtr cont = def->controllers[i];
+                int idx = cont->idx;
+                virDevicePCIAddressPtr addr;
+
+                if (cont->type != VIR_DOMAIN_CONTROLLER_TYPE_PCI)
+                    continue;
+
+                addr = &cont->info.addr.pci;
                 /* check if every PCI bridge controller's ID is greater than
                  * the bus it is placed onto
                  */
-                virDomainControllerDefPtr cont = def->controllers[i];
-                int idx = cont->idx;
-                int bus = cont->info.addr.pci.bus;
-                if (cont->type == VIR_DOMAIN_CONTROLLER_TYPE_PCI &&
-                    cont->model == VIR_DOMAIN_CONTROLLER_MODEL_PCI_BRIDGE &&
-                    idx <= bus) {
+                if (cont->model == VIR_DOMAIN_CONTROLLER_MODEL_PCI_BRIDGE &&
+                    idx <= addr->bus) {
                     virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                                    _("failed to create PCI bridge "
                                      "on bus %d: too many devices with fixed "
                                      "addresses"),
-                                   bus);
+                                   addr->bus);
                     goto cleanup;
                 }
             }