[Qemu-devel] [RFC PATCH v8 14/21] replay: checkpoints

[Pavel Dovgalyuk]

This patch introduces checkpoints that synchronize cpu thread and iothread.
When checkpoint is met in the code all asynchronous events from the queue
are executed.

Signed-off-by: Pavel Dovgalyuk <address@hidden>
---
 block.c                  |   11 ++++++++++
 cpus.c                   |    7 ++++++-
 include/qemu/timer.h     |    6 ++++--
 main-loop.c              |    5 +++++
 qemu-timer.c             |   49 ++++++++++++++++++++++++++++++++++++++--------
 replay/replay-internal.h |    5 ++++-
 replay/replay.c          |   36 ++++++++++++++++++++++++++++++++++
 replay/replay.h          |   21 ++++++++++++++++++++
 stubs/replay.c           |   11 ++++++++++
 vl.c                     |    4 +++-
 10 files changed, 142 insertions(+), 13 deletions(-)

diff --git a/block.c b/block.c
index cbe4a32..a4f45c3 100644
--- a/block.c
+++ b/block.c
@@ -1994,6 +1994,11 @@ void bdrv_drain_all(void)
     BlockDriverState *bs;
 
     while (busy) {
+        if (!replay_checkpoint(CHECKPOINT_BDRV_DRAIN)) {
+            /* Do not wait anymore, we stopped at some place in
+               the middle of execution during replay */
+            return;
+        }
         busy = false;
 
         QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
@@ -2004,6 +2009,12 @@ void bdrv_drain_all(void)
             aio_context_release(aio_context);
         }
     }
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        /* Skip checkpoints from the log */
+        while (replay_checkpoint(CHECKPOINT_BDRV_DRAIN)) {
+            /* Nothing */
+        }
+    }
 }
 
 /* make a BlockDriverState anonymous by removing from bdrv_state and
diff --git a/cpus.c b/cpus.c
index 01d89aa..9c32491 100644
--- a/cpus.c
+++ b/cpus.c
@@ -388,7 +388,7 @@ void qtest_clock_warp(int64_t dest)
         timers_state.qemu_icount_bias += warp;
         seqlock_write_unlock(&timers_state.vm_clock_seqlock);
 
-        qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL);
+        qemu_clock_run_timers(QEMU_CLOCK_VIRTUAL, false);
         clock = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
     }
     qemu_clock_notify(QEMU_CLOCK_VIRTUAL);
@@ -408,6 +408,11 @@ void qemu_clock_warp(QEMUClockType type)
         return;
     }
 
+    /* warp clock deterministically in record/replay mode */
+    if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP)) {
+        return;
+    }
+
     /*
      * If the CPUs have been sleeping, advance QEMU_CLOCK_VIRTUAL timer now.
      * This ensures that the deadline for the timer is computed correctly 
below.
diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 0c2472c..26927b0 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -240,13 +240,14 @@ void qemu_clock_unregister_reset_notifier(QEMUClockType 
type,
 /**
  * qemu_clock_run_timers:
  * @type: clock on which to operate
+ * @run_all: true, when called from qemu_clock_run_all_timers
  *
  * Run all the timers associated with the default timer list
  * of a clock.
  *
  * Returns: true if any timer ran.
  */
-bool qemu_clock_run_timers(QEMUClockType type);
+bool qemu_clock_run_timers(QEMUClockType type, bool run_all);
 
 /**
  * qemu_clock_run_all_timers:
@@ -337,12 +338,13 @@ QEMUClockType timerlist_get_clock(QEMUTimerList 
*timer_list);
 /**
  * timerlist_run_timers:
  * @timer_list: the timer list to use
+ * @run_all: true, when called from qemu_clock_run_all_timers
  *
  * Call all expired timers associated with the timer list.
  *
  * Returns: true if any timer expired
  */
-bool timerlist_run_timers(QEMUTimerList *timer_list);
+bool timerlist_run_timers(QEMUTimerList *timer_list, bool run_all);
 
 /**
  * timerlist_notify:
diff --git a/main-loop.c b/main-loop.c
index 981bcb5..d6e93c3 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -497,6 +497,11 @@ int main_loop_wait(int nonblocking)
     slirp_pollfds_poll(gpollfds, (ret < 0));
 #endif
 
+    /* CPU thread can infinitely wait for event after
+       missing the warp */
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        qemu_clock_warp(QEMU_CLOCK_VIRTUAL);
+    }
     qemu_clock_run_all_timers();
 
     return ret;
diff --git a/qemu-timer.c b/qemu-timer.c
index bc981a2..b6eb7b3 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -465,7 +465,7 @@ bool timer_expired(QEMUTimer *timer_head, int64_t 
current_time)
     return timer_expired_ns(timer_head, current_time * timer_head->scale);
 }
 
-bool timerlist_run_timers(QEMUTimerList *timer_list)
+bool timerlist_run_timers(QEMUTimerList *timer_list, bool run_all)
 {
     QEMUTimer *ts;
     int64_t current_time;
@@ -473,6 +473,32 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
     QEMUTimerCB *cb;
     void *opaque;
 
+    switch (timer_list->clock->type) {
+    case QEMU_CLOCK_REALTIME:
+        break;
+    default:
+    case QEMU_CLOCK_VIRTUAL:
+        if ((replay_mode != REPLAY_MODE_NONE && !runstate_is_running())
+            || !replay_checkpoint(run_all ? CHECKPOINT_CLOCK_VIRTUAL_ALL
+                                          : CHECKPOINT_CLOCK_VIRTUAL)) {
+            return false;
+        }
+        break;
+    case QEMU_CLOCK_HOST:
+        if ((replay_mode != REPLAY_MODE_NONE && !runstate_is_running())
+            || !replay_checkpoint(run_all ? CHECKPOINT_CLOCK_HOST_ALL
+                                          : CHECKPOINT_CLOCK_HOST)) {
+            return false;
+        }
+    case QEMU_CLOCK_VIRTUAL_RT:
+        if ((replay_mode != REPLAY_MODE_NONE && !runstate_is_running())
+            || !replay_checkpoint(run_all ? CHECKPOINT_CLOCK_VIRTUAL_RT_ALL
+                                          : CHECKPOINT_CLOCK_VIRTUAL_RT)) {
+            return false;
+        }
+        break;
+    }
+
     qemu_event_reset(&timer_list->timers_done_ev);
     if (!timer_list->clock->enabled) {
         goto out;
@@ -505,9 +531,9 @@ out:
     return progress;
 }
 
-bool qemu_clock_run_timers(QEMUClockType type)
+bool qemu_clock_run_timers(QEMUClockType type, bool run_all)
 {
-    return timerlist_run_timers(main_loop_tlg.tl[type]);
+    return timerlist_run_timers(main_loop_tlg.tl[type], run_all);
 }
 
 void timerlistgroup_init(QEMUTimerListGroup *tlg,
@@ -532,7 +558,7 @@ bool timerlistgroup_run_timers(QEMUTimerListGroup *tlg)
     QEMUClockType type;
     bool progress = false;
     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
-        progress |= timerlist_run_timers(tlg->tl[type]);
+        progress |= timerlist_run_timers(tlg->tl[type], false);
     }
     return progress;
 }
@@ -541,11 +567,18 @@ int64_t timerlistgroup_deadline_ns(QEMUTimerListGroup 
*tlg)
 {
     int64_t deadline = -1;
     QEMUClockType type;
+    bool play = replay_mode == REPLAY_MODE_PLAY;
     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
         if (qemu_clock_use_for_deadline(tlg->tl[type]->clock->type)) {
-            deadline = qemu_soonest_timeout(deadline,
-                                            timerlist_deadline_ns(
-                                                tlg->tl[type]));
+            if (!play || tlg->tl[type]->clock->type == QEMU_CLOCK_REALTIME) {
+                deadline = qemu_soonest_timeout(deadline,
+                                                timerlist_deadline_ns(
+                                                    tlg->tl[type]));
+            } else {
+                /* Read clock from the replay file and
+                   do not calculate the deadline, based on virtual clock. */
+                qemu_clock_get_ns(tlg->tl[type]->clock->type);
+            }
         }
     }
     return deadline;
@@ -615,7 +648,7 @@ bool qemu_clock_run_all_timers(void)
     QEMUClockType type;
 
     for (type = 0; type < QEMU_CLOCK_MAX; type++) {
-        progress |= qemu_clock_run_timers(type);
+        progress |= qemu_clock_run_timers(type, true);
     }
 
     return progress;
diff --git a/replay/replay-internal.h b/replay/replay-internal.h
index 68b2d45..c0a5800 100755
--- a/replay/replay-internal.h
+++ b/replay/replay-internal.h
@@ -31,7 +31,10 @@ enum ReplayEvents {
     EVENT_SHUTDOWN,
     /* for clock read/writes */
     /* some of grteater codes are reserved for clocks */
-    EVENT_CLOCK
+    EVENT_CLOCK,
+    /* for checkpoint event */
+    /* some of grteater codes are reserved for checkpoints */
+    EVENT_CHECKPOINT = EVENT_CLOCK + REPLAY_CLOCK_COUNT
 };
 
 /* Asynchronous events IDs */
diff --git a/replay/replay.c b/replay/replay.c
index cfa69fa..7c4a801 100755
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -163,3 +163,39 @@ void replay_shutdown_request(void)
         replay_put_event(EVENT_SHUTDOWN);
     }
 }
+
+bool replay_checkpoint(ReplayCheckpoint checkpoint)
+{
+    bool res = false;
+    replay_save_instructions();
+
+    if (replay_file) {
+        if (replay_mode == REPLAY_MODE_PLAY) {
+            replay_mutex_lock();
+            if (!skip_async_events(EVENT_CHECKPOINT + checkpoint)) {
+                if (replay_data_kind == EVENT_ASYNC) {
+                    replay_read_events(checkpoint);
+                    replay_fetch_data_kind();
+                    res = replay_data_kind != EVENT_ASYNC;
+                    replay_mutex_unlock();
+                    return res;
+                }
+                replay_mutex_unlock();
+                return res;
+            }
+            replay_has_unread_data = 0;
+            replay_read_events(checkpoint);
+            replay_fetch_data_kind();
+            res = replay_data_kind != EVENT_ASYNC;
+            replay_mutex_unlock();
+            return res;
+        } else if (replay_mode == REPLAY_MODE_RECORD) {
+            replay_mutex_lock();
+            replay_put_event(EVENT_CHECKPOINT + checkpoint);
+            replay_save_events(checkpoint);
+            replay_mutex_unlock();
+        }
+    }
+
+    return true;
+}
diff --git a/replay/replay.h b/replay/replay.h
index e1c5fcf..39822b4 100755
--- a/replay/replay.h
+++ b/replay/replay.h
@@ -29,6 +29,21 @@ enum ReplayClockKind {
 };
 typedef enum ReplayClockKind ReplayClockKind;
 
+/* IDs of the checkpoints */
+enum ReplayCheckpoint {
+    CHECKPOINT_BDRV_DRAIN,
+    CHECKPOINT_CLOCK_WARP,
+    CHECKPOINT_RESET_REQUESTED,
+    CHECKPOINT_CLOCK_VIRTUAL,
+    CHECKPOINT_CLOCK_VIRTUAL_ALL,
+    CHECKPOINT_CLOCK_HOST,
+    CHECKPOINT_CLOCK_HOST_ALL,
+    CHECKPOINT_CLOCK_VIRTUAL_RT,
+    CHECKPOINT_CLOCK_VIRTUAL_RT_ALL,
+    CHECKPOINT_COUNT
+};
+typedef enum ReplayCheckpoint ReplayCheckpoint;
+
 extern ReplayMode replay_mode;
 
 /* Processing the instructions */
@@ -80,6 +95,12 @@ void replay_get_timedate(struct tm *tm);
 
 /*! Called when qemu shutdown is requested. */
 void replay_shutdown_request(void);
+/*! Should be called at check points in the execution.
+    These check points are skipped, if they were not met.
+    Saves checkpoint in the SAVE mode and validates in the PLAY mode.
+    Returns 0 in PLAY mode if checkpoint was not found.
+    Returns 1 in all other cases. */
+bool replay_checkpoint(ReplayCheckpoint checkpoint);
 
 /* Asynchronous events queue */
 
diff --git a/stubs/replay.c b/stubs/replay.c
index 121bca6..1be3575 100755
--- a/stubs/replay.c
+++ b/stubs/replay.c
@@ -1,4 +1,5 @@
 #include "replay/replay.h"
+#include "sysemu/sysemu.h"
 
 ReplayMode replay_mode;
 
@@ -10,3 +11,13 @@ int64_t replay_read_clock(unsigned int kind)
 {
     return 0;
 }
+
+bool replay_checkpoint(ReplayCheckpoint checkpoint)
+{
+    return 0;
+}
+
+int runstate_is_running(void)
+{
+    return 0;
+}
diff --git a/vl.c b/vl.c
index 905ea8a..86ba385 100644
--- a/vl.c
+++ b/vl.c
@@ -1767,7 +1767,9 @@ static bool main_loop_should_exit(void)
             return true;
         }
     }
-    if (qemu_reset_requested()) {
+    if (qemu_reset_requested_get()
+        && replay_checkpoint(CHECKPOINT_RESET_REQUESTED)) {
+        qemu_reset_requested();
         pause_all_vcpus();
         cpu_synchronize_all_states();
         qemu_system_reset(VMRESET_REPORT);