schema: Fix guest timer specification schema according to the docs

According to the documentation describing various tunables for domain
timers not all the fields are supported by all the driver types. Express
these in the RNG:

- rtc, platform: Only these support the "track" attribute.
- tsc: only one to support "frequency" and "mode" attributes
- hpet, pit: tickpolicy/catchup attribute/element
- kvmclock: no extra attributes are supported

Additionally the attributes of the <catchup> element for
tickpolicy='catchup' are optional according to the parsing code. Express
this in the XML and fix a spurious space added while formatting the
<catchup> element and add tests for it.

docs/schemas/domaincommon.rng

@@ -857,14 +857,12 @@
   </define>
   <define name="timer">
     <element name="timer">
+      <choice>
+        <group>
           <attribute name="name">
             <choice>
               <value>platform</value>
-          <value>hpet</value>
-          <value>kvmclock</value>
-          <value>pit</value>
               <value>rtc</value>
-          <value>tsc</value>
             </choice>
           </attribute>
           <optional>
@@ -877,17 +875,15 @@
             </attribute>
           </optional>
           <optional>
-        <attribute name="tickpolicy">
-          <choice>
-            <value>delay</value>
-            <value>catchup</value>
-            <value>merge</value>
-            <value>discard</value>
-          </choice>
-        </attribute>
+            <ref name="tickpolicy"/>
           </optional>
+        </group>
+        <group>
+          <attribute name="name">
+            <value>tsc</value>
+          </attribute>
           <optional>
-        <ref name="catchup"/>
+            <ref name="tickpolicy"/>
           </optional>
           <optional>
             <attribute name="frequency">
@@ -905,6 +901,24 @@
               </choice>
             </attribute>
           </optional>
+        </group>
+        <group>
+          <attribute name="name">
+            <choice>
+              <value>hpet</value>
+              <value>pit</value>
+            </choice>
+          </attribute>
+          <optional>
+            <ref name="tickpolicy"/>
+          </optional>
+        </group>
+        <group>
+          <attribute name="name">
+            <value>kvmclock</value>
+          </attribute>
+        </group>
+      </choice>
       <optional>
         <attribute name="present">
           <choice>
@@ -916,20 +930,43 @@
       <empty/>
     </element>
   </define>
-  <define name="catchup">
+
+  <define name="tickpolicy">
+    <choice>
+      <group>
+        <attribute name="tickpolicy">
+          <choice>
+            <value>delay</value>
+            <value>merge</value>
+            <value>discard</value>
+          </choice>
+        </attribute>
+      </group>
+      <group>
+        <attribute name="tickpolicy">
+          <value>catchup</value>
+        </attribute>
+        <optional>
           <element name="catchup">
             <optional>
               <attribute name="threshold">
                 <ref name="unsignedInt"/>
               </attribute>
+            </optional>
+            <optional>
               <attribute name="slew">
                 <ref name="unsignedInt"/>
               </attribute>
+            </optional>
+            <optional>
               <attribute name="limit">
                 <ref name="unsignedInt"/>
               </attribute>
             </optional>
           </element>
+        </optional>
+      </group>
+    </choice>
   </define>
 <!--
       A bootloader may be used to extract the OS information instead of

tests/qemuxml2argvdata/qemuxml2argv-clock-catchup.args

@@ -0,0 +1,5 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
+/usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic \
+-monitor unix:/tmp/test-monitor,server,nowait -rtc base=utc,driftfix=slew \
+-no-acpi -boot c -usb -hda /dev/HostVG/QEMUGuest1 \
+-net none -serial none -parallel none

tests/qemuxml2argvdata/qemuxml2argv-clock-catchup.xml

@@ -0,0 +1,37 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'>
+    <timer name='rtc' tickpolicy='catchup'>
+      <catchup slew='4636'/>
+    </timer>
+    <timer name='pit' tickpolicy='catchup'>
+      <catchup threshold='123'/>
+    </timer>
+    <timer name='hpet' tickpolicy='catchup'>
+      <catchup limit='2342'/>
+    </timer>
+  </clock>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -633,6 +633,7 @@ mymain(void)
     DO_TEST("clock-france", QEMU_CAPS_RTC);
     DO_TEST("clock-hpet-off", QEMU_CAPS_RTC, QEMU_CAPS_NO_HPET,
             QEMU_CAPS_NO_KVM_PIT);
+    DO_TEST("clock-catchup", QEMU_CAPS_RTC, QEMU_CAPS_NO_KVM_PIT);
     DO_TEST("cpu-kvmclock", QEMU_CAPS_ENABLE_KVM);
     DO_TEST("cpu-host-kvmclock", QEMU_CAPS_ENABLE_KVM, QEMU_CAPS_CPU_HOST);
     DO_TEST("kvmclock", QEMU_CAPS_KVM);

tests/qemuxml2xmltest.c

@@ -158,6 +158,7 @@ mymain(void)
     DO_TEST("clock-localtime");
     DO_TEST("cpu-kvmclock");
     DO_TEST("cpu-host-kvmclock");
+    DO_TEST("clock-catchup");
     DO_TEST("kvmclock");
 
     DO_TEST("cpu-eoi-disabled");