introduce and use qemu_clock_enable

By adding the possibility to turn on/off a clock, yet another
incestuous relationship between timers and CPUs can be disentangled.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

vl.c

@@ -578,6 +578,7 @@ void cpu_disable_ticks(void)
 
 struct QEMUClock {
     int type;
+    int enabled;
     /* XXX: add frequency */
 };
 
@@ -812,9 +813,15 @@ static QEMUClock *qemu_new_clock(int type)
     QEMUClock *clock;
     clock = qemu_mallocz(sizeof(QEMUClock));
     clock->type = type;
+    clock->enabled = 1;
     return clock;
 }
 
+static void qemu_clock_enable(QEMUClock *clock, int enabled)
+{
+    clock->enabled = enabled;
+}
+
 QEMUTimer *qemu_new_timer(QEMUClock *clock, QEMUTimerCB *cb, void *opaque)
 {
     QEMUTimer *ts;
@@ -907,6 +914,9 @@ static void qemu_run_timers(QEMUClock *clock)
 {
     QEMUTimer **ptimer_head, *ts;
     int64_t current_time;
+
+    if (!clock->enabled)
+        return;
 
     current_time = qemu_get_clock (clock);
     ptimer_head = &active_timers[clock->type];
@@ -1017,8 +1027,7 @@ static void qemu_run_all_timers(void)
 
     /* vm time timers */
     if (vm_running) {
-        if (!cur_cpu || likely(!(cur_cpu->singlestep_enabled & SSTEP_NOTIMER)))
-            qemu_run_timers(vm_clock);
+        qemu_run_timers(vm_clock);
     }
 
     qemu_run_timers(rt_clock);
@@ -3969,6 +3978,9 @@ static void tcg_cpu_exec(void)
     for (; next_cpu != NULL; next_cpu = next_cpu->next_cpu) {
         CPUState *env = cur_cpu = next_cpu;
 
+        qemu_clock_enable(vm_clock,
+                          (cur_cpu->singlestep_enabled & SSTEP_NOTIMER) == 0);
+
         if (alarm_timer->pending)
             break;
         if (cpu_can_run(env))