qemu: Fix auto-adding PCI bridge when all slots are reserved

Commit 93c8ca tried to fix the issue with auto-adding of a PCI bridge
controller, but didn't work properly in all scenarios.

This patch provides a better fix of the issue when all slots on a PCI bus
are reserved by devices with user specified addresses and no additional
bridges need to be created.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1132900

src/qemu/qemu_command.c

@@ -1910,6 +1910,8 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
         int nbuses = 0;
         size_t i;
         int rv;
+        bool buses_reserved = true;
+
         virDomainPCIConnectFlags flags = VIR_PCI_CONNECT_TYPE_PCI;
 
         for (i = 0; i < def->ncontrollers; i++) {
@@ -1932,18 +1934,21 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
             if (qemuValidateDevicePCISlotsChipsets(def, qemuCaps, addrs) < 0)
                 goto cleanup;
 
-            if (qemuAssignDevicePCISlots(def, addrs) < 0)
-                goto cleanup;
-
             for (i = 0; i < addrs->nbuses; i++) {
-                if (!qemuDomainPCIBusFullyReserved(&addrs->buses[i])) {
-
-                    /* Reserve 1 extra slot for a (potential) bridge */
-                    if (virDomainPCIAddressReserveNextSlot(addrs, &info, flags) < 0)
-                        goto cleanup;
-                }
+                if (!qemuDomainPCIBusFullyReserved(&addrs->buses[i]))
+                    buses_reserved = false;
             }
 
+            /* Reserve 1 extra slot for a (potential) bridge only if buses
+             * are not fully reserved yet
+             */
+            if (!buses_reserved &&
+                virDomainPCIAddressReserveNextSlot(addrs, &info, flags) < 0)
+                goto cleanup;
+
+            if (qemuAssignDevicePCISlots(def, addrs) < 0)
+                goto cleanup;
+
             for (i = 1; i < addrs->nbuses; i++) {
                 virDomainPCIAddressBusPtr bus = &addrs->buses[i];