qemu: add a USB3 controller to Q35 domains by default

Previously we added a set of EHCI+UHCI controllers to Q35 machines to
mimic real hardware as closely as possible, but recent discussions
have pointed out that the nec-usb-xhci (USB3) controller is much more
virtualization-friendly (uses less CPU), so this patch switches the
default for Q35 machinetypes to add an XHCI instead (if it's
supported, which it of course *will* be).

Since none of the existing test cases left out USB controllers in the
input XML, a new Q35 test case was added which has *no* devices, so
ends up with only the defaults always put in by qemu, plus those added
by libvirt.

src/qemu/qemu_domain.c

@@ -2190,10 +2190,14 @@ qemuDomainDefAddDefaultDevices(virDomainDefPtr def,
             addPCIeRoot = true;
             addImplicitSATA = true;
 
-            /* add a USB2 controller set, but only if the
-             * ich9-usb-ehci1 device is supported
+            /* Prefer adding USB3 controller if supported
+             * (nec-usb-xhci). Failing that, add a USB2 controller set
+             * if the ich9-usb-ehci1 device is supported. Otherwise
+             * don't add anything.
              */
-            if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_ICH9_USB_EHCI1))
+            if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_NEC_USB_XHCI))
+                usbModel = VIR_DOMAIN_CONTROLLER_MODEL_USB_NEC_XHCI;
+            else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_ICH9_USB_EHCI1))
                 usbModel = VIR_DOMAIN_CONTROLLER_MODEL_USB_ICH9_EHCI1;
             else
                 addDefaultUSB = false;

tests/qemuxml2argvdata/qemuxml2argv-q35-default-devices-only.args

@@ -0,0 +1,22 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/libexec/qemu-kvm \
+-name q35-test \
+-S \
+-M q35 \
+-m 2048 \
+-smp 2,sockets=2,cores=1,threads=1 \
+-uuid 11dbdcdd-4c3b-482b-8903-9bdb8c0a2774 \
+-nographic \
+-nodefaults \
+-monitor unix:/tmp/lib/domain--1-q35-test/monitor.sock,server,nowait \
+-no-acpi \
+-boot c \
+-device ioh3420,port=0x8,chassis=1,id=pci.1,bus=pcie.0,addr=0x1 \
+-device ioh3420,port=0x10,chassis=2,id=pci.2,bus=pcie.0,addr=0x2 \
+-device nec-usb-xhci,id=usb,bus=pci.1,addr=0x0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.2,addr=0x0

tests/qemuxml2argvdata/qemuxml2argv-q35-default-devices-only.xml

@@ -0,0 +1,18 @@
+<domain type='qemu'>
+  <name>q35-test</name>
+  <uuid>11dbdcdd-4c3b-482b-8903-9bdb8c0a2774</uuid>
+  <memory unit='KiB'>2097152</memory>
+  <currentMemory unit='KiB'>2097152</currentMemory>
+  <vcpu placement='static' cpuset='0-1'>2</vcpu>
+  <os>
+    <type arch='x86_64' machine='q35'>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/libexec/qemu-kvm</emulator>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1844,6 +1844,29 @@ mymain(void)
             QEMU_CAPS_ICH9_USB_EHCI1,
             QEMU_CAPS_NEC_USB_XHCI,
             QEMU_CAPS_DEVICE_VIDEO_PRIMARY);
+    DO_TEST("q35-default-devices-only",
+            QEMU_CAPS_VIRTIO_PCI_DISABLE_LEGACY,
+            QEMU_CAPS_DEVICE_VIRTIO_RNG,
+            QEMU_CAPS_OBJECT_RNG_RANDOM,
+            QEMU_CAPS_NETDEV,
+            QEMU_CAPS_DEVICE_VIRTIO_NET,
+            QEMU_CAPS_DEVICE_VIRTIO_GPU,
+            QEMU_CAPS_VIRTIO_GPU_VIRGL,
+            QEMU_CAPS_VIRTIO_KEYBOARD,
+            QEMU_CAPS_VIRTIO_MOUSE,
+            QEMU_CAPS_VIRTIO_TABLET,
+            QEMU_CAPS_VIRTIO_INPUT_HOST,
+            QEMU_CAPS_VIRTIO_SCSI,
+            QEMU_CAPS_FSDEV,
+            QEMU_CAPS_FSDEV_WRITEOUT,
+            QEMU_CAPS_DEVICE_PCI_BRIDGE,
+            QEMU_CAPS_DEVICE_DMI_TO_PCI_BRIDGE,
+            QEMU_CAPS_DEVICE_IOH3420,
+            QEMU_CAPS_ICH9_AHCI,
+            QEMU_CAPS_PCI_MULTIFUNCTION,
+            QEMU_CAPS_ICH9_USB_EHCI1,
+            QEMU_CAPS_NEC_USB_XHCI,
+            QEMU_CAPS_DEVICE_VIDEO_PRIMARY);
     DO_TEST("pcie-root-port",
             QEMU_CAPS_DEVICE_PCI_BRIDGE,
             QEMU_CAPS_DEVICE_DMI_TO_PCI_BRIDGE,

tests/qemuxml2xmloutdata/qemuxml2xmlout-q35-default-devices-only.xml

@@ -0,0 +1,40 @@
+<domain type='qemu'>
+  <name>q35-test</name>
+  <uuid>11dbdcdd-4c3b-482b-8903-9bdb8c0a2774</uuid>
+  <memory unit='KiB'>2097152</memory>
+  <currentMemory unit='KiB'>2097152</currentMemory>
+  <vcpu placement='static' cpuset='0-1'>2</vcpu>
+  <os>
+    <type arch='x86_64' machine='q35'>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/libexec/qemu-kvm</emulator>
+    <controller type='usb' index='0' model='nec-xhci'>
+      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
+    </controller>
+    <controller type='sata' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
+    </controller>
+    <controller type='pci' index='0' model='pcie-root'/>
+    <controller type='pci' index='1' model='pcie-root-port'>
+      <model name='ioh3420'/>
+      <target chassis='1' port='0x8'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
+    </controller>
+    <controller type='pci' index='2' model='pcie-root-port'>
+      <model name='ioh3420'/>
+      <target chassis='2' port='0x10'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
+    </controller>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'>
+      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
+    </memballoon>
+  </devices>
+</domain>

tests/qemuxml2xmltest.c

@@ -765,6 +765,29 @@ mymain(void)
             QEMU_CAPS_ICH9_USB_EHCI1,
             QEMU_CAPS_NEC_USB_XHCI,
             QEMU_CAPS_DEVICE_VIDEO_PRIMARY);
+    DO_TEST("q35-default-devices-only",
+            QEMU_CAPS_VIRTIO_PCI_DISABLE_LEGACY,
+            QEMU_CAPS_DEVICE_VIRTIO_RNG,
+            QEMU_CAPS_OBJECT_RNG_RANDOM,
+            QEMU_CAPS_NETDEV,
+            QEMU_CAPS_DEVICE_VIRTIO_NET,
+            QEMU_CAPS_DEVICE_VIRTIO_GPU,
+            QEMU_CAPS_VIRTIO_GPU_VIRGL,
+            QEMU_CAPS_VIRTIO_KEYBOARD,
+            QEMU_CAPS_VIRTIO_MOUSE,
+            QEMU_CAPS_VIRTIO_TABLET,
+            QEMU_CAPS_VIRTIO_INPUT_HOST,
+            QEMU_CAPS_VIRTIO_SCSI,
+            QEMU_CAPS_FSDEV,
+            QEMU_CAPS_FSDEV_WRITEOUT,
+            QEMU_CAPS_DEVICE_PCI_BRIDGE,
+            QEMU_CAPS_DEVICE_DMI_TO_PCI_BRIDGE,
+            QEMU_CAPS_DEVICE_IOH3420,
+            QEMU_CAPS_ICH9_AHCI,
+            QEMU_CAPS_PCI_MULTIFUNCTION,
+            QEMU_CAPS_ICH9_USB_EHCI1,
+            QEMU_CAPS_NEC_USB_XHCI,
+            QEMU_CAPS_DEVICE_VIDEO_PRIMARY);
     DO_TEST("pcie-root",
             QEMU_CAPS_DEVICE_PCI_BRIDGE, QEMU_CAPS_DEVICE_DMI_TO_PCI_BRIDGE,
             QEMU_CAPS_DEVICE_IOH3420, QEMU_CAPS_ICH9_AHCI,