CPUIDLE: Avoid remnant LAPIC timer intr while force hpetbroadcast

LAPIC will stop during C3, and resume to work after exit from
C3. Considering below case:
The LAPIC timer was programmed to expire after 1000us, but CPU enter
C3 after 100us and exit C3 at 9xxus.

   0us: reprogram_timer(1000us)
 100us: entry C3, LAPIC timer stop
 9xxus: exit C3 due to unexpected event, LAPIC timer continue running
10xxus: reprogram_timer(1000us), fail due to the past expiring time.
......: no timer softirq raised, no change to LAPIC timer.
......: if entry C3 again, HPET will be forced reprogramed to
 now+small_slop.
......: if entry C2, no change to LAPIC.
18xxus: LAPIC timer expires unexpectedly if no C3 entries after
 10xxus.

Signed-off-by: Wei Gang <gang.wei@intel.com>

diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index 31028cc2a6a65a12cd581a086eab23451f58b890..3857cb0af6e7e15f7e1cfd49157e04707f029757 100644 (file)
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -233,7 +233,15 @@ void hpet_broadcast_exit(void)
 
     if ( cpu_test_and_clear(cpu, ch->cpumask) )
     {
-        reprogram_timer(per_cpu(timer_deadline, cpu));
+        if ( !reprogram_timer(per_cpu(timer_deadline, cpu)) )
+        {
+            /*
+             * The deadline must have passed -- trigger timer work now.
+             * Also cancel any outstanding LAPIC event.
+             */
+            reprogram_timer(0);
+            raise_softirq(TIMER_SOFTIRQ);
+        }
 
         if ( cpus_empty(ch->cpumask) && ch->next_event != STIME_MAX )
             reprogram_hpet_evt_channel(ch, STIME_MAX, 0, 0);