qemu: Allow to specify pit timer tick policy=discard

Separate out the "policy=discard" into it's own specific
qemu command line.

We'll rename "kvm-pit-device" test case to be "kvm-pit-discard"
since it has the syntax we'd be using.

Signed-off-by: Maxim Nestratov <mnestratov@virtuozzo.com>

src/qemu/qemu_command.c

@@ -6261,9 +6261,15 @@ qemuBuildClockCommandLine(virCommandPtr cmd,
                     return -1;
                 }
                 break;
-            case VIR_DOMAIN_TIMER_TICKPOLICY_MERGE:
             case VIR_DOMAIN_TIMER_TICKPOLICY_DISCARD:
-                /* no way to support these modes for pit in qemu */
+                if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_KVM_PIT_TICK_POLICY))
+                    virCommandAddArgList(cmd, "-global",
+                                         "kvm-pit.lost_tick_policy=discard", NULL);
+                else if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_NO_KVM_PIT))
+                    virCommandAddArg(cmd, "-no-kvm-pit-reinjection");
+                break;
+            case VIR_DOMAIN_TIMER_TICKPOLICY_MERGE:
+                /* no way to support this mode for pit in qemu */
                 virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                                _("unsupported pit tickpolicy '%s'"),
                                virDomainTimerTickpolicyTypeToString(def->clock.timers[i]->tickpolicy));

tests/qemuxml2argvdata/qemuxml2argv-kvm-pit-discard.xml

@@ -9,7 +9,7 @@
     <boot dev='hd'/>
   </os>
   <clock offset='utc'>
-    <timer name='pit' tickpolicy='delay'/>
+    <timer name='pit' tickpolicy='discard'/>
   </clock>
   <on_poweroff>destroy</on_poweroff>
   <on_reboot>restart</on_reboot>

tests/qemuxml2argvtest.c

@@ -2275,6 +2275,7 @@ mymain(void)
     qemuTestSetHostArch(driver.caps, VIR_ARCH_NONE);
 
     DO_TEST("kvm-pit-delay", QEMU_CAPS_KVM_PIT_TICK_POLICY);
+    DO_TEST("kvm-pit-discard", QEMU_CAPS_KVM_PIT_TICK_POLICY);
 
     DO_TEST("panic", QEMU_CAPS_DEVICE_PANIC,
             QEMU_CAPS_NODEFCONFIG);