libxl: fix timer configuration

The current logic around configuring timers in libxl based on
virDomainDef object is a bit brain dead. Unsupported timers are
silently ignored and tsc is only recognized if it is the first
timer specified.

Change the logic to reject unsupported timers and honor the tsc
timer regardless of its order when multiple timers are specified.

src/libxl/libxl_conf.c

@@ -313,9 +313,10 @@ libxlMakeDomBuildInfo(virDomainDefPtr def,
     for (i = 0; i < virDomainDefGetVcpus(def); i++)
         libxl_bitmap_set((&b_info->avail_vcpus), i);
 
-    if (def->clock.ntimers > 0 &&
-        def->clock.timers[0]->name == VIR_DOMAIN_TIMER_NAME_TSC) {
-        switch (def->clock.timers[0]->mode) {
+    for (i = 0; i < def->clock.ntimers; i++) {
+        switch ((virDomainTimerNameType) def->clock.timers[i]->name) {
+        case VIR_DOMAIN_TIMER_NAME_TSC:
+            switch (def->clock.timers[i]->mode) {
             case VIR_DOMAIN_TIMER_MODE_NATIVE:
                 b_info->tsc_mode = 2;
                 break;
@@ -324,8 +325,35 @@ libxlMakeDomBuildInfo(virDomainDefPtr def,
                 break;
             default:
                 b_info->tsc_mode = 1;
+            }
+            break;
+
+        case VIR_DOMAIN_TIMER_NAME_HPET:
+            if (!hvm) {
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("unsupported timer type (name) '%s'"),
+                               virDomainTimerNameTypeToString(def->clock.timers[i]->name));
+                return -1;
+            }
+            if (def->clock.timers[i]->present == 1)
+                libxl_defbool_set(&b_info->u.hvm.hpet, 1);
+            break;
+
+        case VIR_DOMAIN_TIMER_NAME_PLATFORM:
+        case VIR_DOMAIN_TIMER_NAME_KVMCLOCK:
+        case VIR_DOMAIN_TIMER_NAME_HYPERVCLOCK:
+        case VIR_DOMAIN_TIMER_NAME_RTC:
+        case VIR_DOMAIN_TIMER_NAME_PIT:
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("unsupported timer type (name) '%s'"),
+                           virDomainTimerNameTypeToString(def->clock.timers[i]->name));
+            return -1;
+
+        case VIR_DOMAIN_TIMER_NAME_LAST:
+            break;
         }
     }
+
     b_info->sched_params.weight = 1000;
     b_info->max_memkb = virDomainDefGetMemoryInitial(def);
     b_info->target_memkb = def->mem.cur_balloon;
@@ -341,12 +369,6 @@ libxlMakeDomBuildInfo(virDomainDefPtr def,
         libxl_defbool_set(&b_info->u.hvm.acpi,
                           def->features[VIR_DOMAIN_FEATURE_ACPI] ==
                           VIR_TRISTATE_SWITCH_ON);
-        for (i = 0; i < def->clock.ntimers; i++) {
-            if (def->clock.timers[i]->name == VIR_DOMAIN_TIMER_NAME_HPET &&
-                def->clock.timers[i]->present == 1) {
-                libxl_defbool_set(&b_info->u.hvm.hpet, 1);
-            }
-        }
 
         if (def->nsounds > 0) {
             /*