replay: ptimer

This patch adds deterministic replay for hardware periodic countdown timers.
ptimer uses bottom halves layer to execute such an asynchronous callback.
We put this callback into the replay queue instead of bottom halves one.
When checkpoint is met by main loop thread, the replay queue is processed
and callback is executed. Binding callback moment to one of the checkpoints
makes it deterministic.
Signed-off-by: NPavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162456.8676.83366.stgit@PASHA-ISP.def.inno>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>

hw/core/ptimer.c

@@ -9,6 +9,7 @@
 #include "qemu/timer.h"
 #include "hw/ptimer.h"
 #include "qemu/host-utils.h"
+#include "sysemu/replay.h"
 
 struct ptimer_state
 {
@@ -27,7 +28,7 @@ struct ptimer_state
 static void ptimer_trigger(ptimer_state *s)
 {
     if (s->bh) {
-        qemu_bh_schedule(s->bh);
+        replay_bh_schedule_event(s->bh);
     }
 }
 

include/sysemu/replay.h

@@ -15,6 +15,7 @@
 #include <stdbool.h>
 #include <stdint.h>
 #include "qapi-types.h"
+#include "qemu/typedefs.h"
 
 /* replay clock kinds */
 enum ReplayClockKind {
@@ -97,5 +98,7 @@ bool replay_checkpoint(ReplayCheckpoint checkpoint);
 void replay_disable_events(void);
 /*! Returns true when saving events is enabled */
 bool replay_events_enabled(void);
+/*! Adds bottom half event to the queue */
+void replay_bh_schedule_event(QEMUBH *bh);
 
 #endif

replay/replay-events.c

@@ -13,6 +13,7 @@
 #include "qemu/error-report.h"
 #include "sysemu/replay.h"
 #include "replay-internal.h"
+#include "block/aio.h"
 
 typedef struct Event {
     ReplayAsyncEventKind event_kind;
@@ -35,6 +36,9 @@ static bool events_enabled;
 static void replay_run_event(Event *event)
 {
     switch (event->event_kind) {
+    case REPLAY_ASYNC_EVENT_BH:
+        aio_bh_call(event->opaque);
+        break;
     default:
         error_report("Replay: invalid async event ID (%d) in the queue",
                     event->event_kind);
@@ -89,7 +93,6 @@ void replay_clear_events(void)
 }
 
 /*! Adds specified async event to the queue */
-#if 0
 static void replay_add_event(ReplayAsyncEventKind event_kind,
                              void *opaque,
                              void *opaque2, uint64_t id)
@@ -117,7 +120,16 @@ static void replay_add_event(ReplayAsyncEventKind event_kind,
     QTAILQ_INSERT_TAIL(&events_list, event, events);
     replay_mutex_unlock();
 }
-#endif
+
+void replay_bh_schedule_event(QEMUBH *bh)
+{
+    if (replay_mode != REPLAY_MODE_NONE) {
+        uint64_t id = replay_get_current_step();
+        replay_add_event(REPLAY_ASYNC_EVENT_BH, bh, NULL, id);
+    } else {
+        qemu_bh_schedule(bh);
+    }
+}
 
 static void replay_save_event(Event *event, int checkpoint)
 {
@@ -129,10 +141,12 @@ static void replay_save_event(Event *event, int checkpoint)
 
         /* save event-specific data */
         switch (event->event_kind) {
+        case REPLAY_ASYNC_EVENT_BH:
+            replay_put_qword(event->id);
+            break;
         default:
             error_report("Unknown ID %d of replay event", read_event_kind);
             exit(1);
-            break;
         }
     }
 }
@@ -168,6 +182,11 @@ static Event *replay_read_event(int checkpoint)
 
     /* Events that has not to be in the queue */
     switch (read_event_kind) {
+    case REPLAY_ASYNC_EVENT_BH:
+        if (read_id == -1) {
+            read_id = replay_get_qword();
+        }
+        break;
     default:
         error_report("Unknown ID %d of replay event", read_event_kind);
         exit(1);

replay/replay-internal.h

@@ -39,6 +39,7 @@ enum ReplayEvents {
 /* Asynchronous events IDs */
 
 enum ReplayAsyncEventKind {
+    REPLAY_ASYNC_EVENT_BH,
     REPLAY_ASYNC_COUNT
 };