qemu: reserve PCI addresses for implicit i440fx devices

Somewhere around commit 9ff9d9f5 reserving entire PCI slots was
eliminated, as demonstrated by commit 6cc20142.

Reserve the functions required by the implicit devices:
00:01.0 ISA Bridge
00:01.1 IDE Controller
00:01.2 USB Controller (unless USB is disabled)
00:01.3 Bridge

https://bugzilla.redhat.com/show_bug.cgi?id=1460143

src/qemu/qemu_domain_address.c

@@ -1429,15 +1429,24 @@ qemuDomainValidateDevicePCISlotsPIIX3(virDomainDefPtr def,
                 cont->info.addr.pci.slot = 1;
                 cont->info.addr.pci.function = 2;
             }
+        } else {
+            /* this controller is not skipped in qemuDomainCollectPCIAddress */
+            continue;
         }
+        if (addrs->nbuses &&
+            virDomainPCIAddressReserveAddr(addrs, &cont->info.addr.pci, flags, 0) < 0)
+            goto cleanup;
     }
 
-    /* PIIX3 (ISA bridge, IDE controller, something else unknown, USB controller)
-     * hardcoded slot=1, multifunction device
-     */
+    /* Implicit PIIX3 devices living on slot 1 not handled above */
     if (addrs->nbuses) {
         memset(&tmp_addr, 0, sizeof(tmp_addr));
         tmp_addr.slot = 1;
+        /* ISA Bridge at 00:01.0 */
+        if (virDomainPCIAddressReserveAddr(addrs, &tmp_addr, flags, 0) < 0)
+            goto cleanup;
+        /* Bridge at 00:01.3 */
+        tmp_addr.function = 3;
         if (virDomainPCIAddressReserveAddr(addrs, &tmp_addr, flags, 0) < 0)
             goto cleanup;
     }

tests/qemuxml2argvdata/qemuxml2argv-440fx-ide-address-conflict.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-i686</emulator>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'>
+      <address type='pci' slot='1' function='1'/>
+    </memballoon>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -2259,6 +2259,7 @@ mymain(void)
             QEMU_CAPS_DEVICE_VIDEO_PRIMARY,
             QEMU_CAPS_DEVICE_QXL);
     DO_TEST_PARSE_ERROR("440fx-wrong-root", NONE);
+    DO_TEST_PARSE_ERROR("440fx-ide-address-conflict", NONE);
 
     DO_TEST_PARSE_ERROR("pcie-root-port-too-many",
             QEMU_CAPS_DEVICE_IOH3420,