qemu: prefer to put a Q35 machine's dmi-to-pci-bridge at 00:1E.0

This resolves one of the issues listed in:

   https://bugzilla.redhat.com/show_bug.cgi?id=1003983

00:1E.0 is the location of this controller on at least some actual Q35
hardware, so we try to replicate the placement. The bridge should work
just as well in any other location though, so if 00:1E.0 isn't
available, just allow it to be auto-assigned anywhere appropriate.

src/qemu/qemu_command.c

@@ -2560,6 +2560,28 @@ qemuDomainValidateDevicePCISlotsQ35(virDomainDefPtr def,
                 }
             }
             break;
+
+        case VIR_DOMAIN_CONTROLLER_TYPE_PCI:
+            if (def->controllers[i]->model == VIR_DOMAIN_CONTROLLER_MODEL_DMI_TO_PCI_BRIDGE &&
+                def->controllers[i]->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_NONE) {
+                /* Try to assign this bridge to 00:1E.0 (because that
+                * is its standard location on real hardware) unless
+                * it's already taken, but don't insist on it.
+                */
+                memset(&tmp_addr, 0, sizeof(tmp_addr));
+                tmp_addr.slot = 0x1E;
+                if (!qemuDomainPCIAddressSlotInUse(addrs, &tmp_addr)) {
+                    if (qemuDomainPCIAddressReserveAddr(addrs, &tmp_addr,
+                                                        flags, true, false) < 0)
+                        goto cleanup;
+                    def->controllers[i]->info.type = VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI;
+                    def->controllers[i]->info.addr.pci.domain = 0;
+                    def->controllers[i]->info.addr.pci.bus = 0;
+                    def->controllers[i]->info.addr.pci.slot = 0x1E;
+                    def->controllers[i]->info.addr.pci.function = 0;
+                }
+            }
+            break;
         }
     }
 

tests/qemuxml2argvdata/qemuxml2argv-pcie-root.args

@@ -2,5 +2,5 @@ LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
 /usr/libexec/qemu-kvm \
 -S -M q35 -m 2048 -smp 2 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
--device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x2 \
+-device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1e \
 -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1

tests/qemuxml2argvdata/qemuxml2argv-pcihole64-q35.args

@@ -2,7 +2,7 @@ LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
 /usr/libexec/qemu-kvm -S -M q35 -m 2048 -smp 2 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi \
 -boot c -global q35-pcihost.pci-hole64-size=1048576K \
--device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x2 \
+-device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1e \
 -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1 \
 -drive file=/dev/HostVG/QEMUGuest1,if=none,id=drive-sata0-0-0 \
 -device ide-drive,bus=ide.0,drive=drive-sata0-0-0,id=sata0-0-0 \

tests/qemuxml2argvdata/qemuxml2argv-q35.args

 LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
 /usr/libexec/qemu-kvm -S -M q35 -m 2048 -smp 2 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
--device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x2 \
+-device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x1e \
 -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1 \
 -drive file=/dev/HostVG/QEMUGuest1,if=none,id=drive-sata0-0-0 \
 -device ide-drive,bus=ide.0,drive=drive-sata0-0-0,id=sata0-0-0 \