qemu: report a nicer error when USB is disabled

If the user tries to define a domain that has

  <controller type='usb' model='none'/>

and also some USB devices, we report an error:
  error: internal error: No free USB ports

Which is technically still correct for a domain with no USB ports.

Change it to:

USB is disabled for this domain, but USB devices are present in the domain XML

https://bugzilla.redhat.com/show_bug.cgi?id=1347550Signed-off-by: NJán Tomko <jtomko@redhat.com>

src/conf/domain_conf.c

@@ -5225,7 +5225,7 @@ virDomainDiskDefValidate(const virDomainDiskDef *disk)
     return 0;
 }
 
-static bool
+bool
 virDomainDefHasUSB(const virDomainDef *def)
 {
     size_t i;

src/conf/domain_conf.h

@@ -2700,6 +2700,8 @@ int virDomainDefPostParse(virDomainDefPtr def,
                           unsigned int parseFlags,
                           virDomainXMLOptionPtr xmlopt,
                           void *parseOpaque);
+bool
+virDomainDefHasUSB(const virDomainDef *def);
 
 int virDomainDeviceValidateAliasForHotplug(virDomainObjPtr vm,
                                            virDomainDeviceDefPtr dev,

src/libvirt_private.syms

@@ -276,6 +276,7 @@ virDomainDefGetVcpusTopology;
 virDomainDefHasDeviceAddress;
 virDomainDefHasMemballoon;
 virDomainDefHasMemoryHotplug;
+virDomainDefHasUSB;
 virDomainDefHasVcpusOffline;
 virDomainDefLifecycleActionAllowed;
 virDomainDefMaybeAddController;

src/qemu/qemu_domain_address.c

@@ -2701,6 +2701,13 @@ qemuDomainUSBAddressAddHubs(virDomainDefPtr def)
                                               &data,
                                               false));
 
+    if (data.count && !virDomainDefHasUSB(def)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("USB is disabled for this domain, but USB devices "
+                         "are present in the domain XML"));
+        return -1;
+    }
+
     if (data.count > available_ports)
         hubs_needed = VIR_DIV_UP(data.count - available_ports + 1,
                                  VIR_DOMAIN_USB_HUB_PORTS - 1);