[Qemu-devel] [RFC PATCH v11 14/23] replay: checkpoints

[Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>]

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 <pavel.dovgaluk@ispras.ru>
---
 cpus.c                   |    5 +++++
 main-loop.c              |    6 ++++++
 qemu-timer.c             |   38 ++++++++++++++++++++++++++++++++++----
 replay/replay-internal.h |    4 ++++
 replay/replay.c          |   34 ++++++++++++++++++++++++++++++++++
 replay/replay.h          |   19 +++++++++++++++++++
 stubs/replay.c           |   11 +++++++++++
 vl.c                     |   13 ++++++++++++-
 8 files changed, 125 insertions(+), 5 deletions(-)

diff --git a/cpus.c b/cpus.c
index 3f33e0c..f6e0c44 100644
--- a/cpus.c
+++ b/cpus.c
@@ -395,6 +395,11 @@ 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/main-loop.c b/main-loop.c
index 981bcb5..06aad06 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -29,6 +29,7 @@
 #include "slirp/libslirp.h"
 #include "qemu/main-loop.h"
 #include "block/aio.h"
+#include "replay/replay.h"
 
 #ifndef _WIN32
 
@@ -497,6 +498,11 @@ 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 d605afd..37d9098 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -478,10 +478,33 @@ bool timerlist_run_timers(QEMUTimerList *timer_list)
     void *opaque;
 
     qemu_event_reset(&timer_list->timers_done_ev);
-    if (!timer_list->clock->enabled) {
+    if (!timer_list->clock->enabled || !timer_list->active_timers) {
         goto out;
     }
 
+    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(CHECKPOINT_CLOCK_VIRTUAL)) {
+            goto out;
+        }
+        break;
+    case QEMU_CLOCK_HOST:
+        if ((replay_mode != REPLAY_MODE_NONE && !runstate_is_running())
+            || !replay_checkpoint(CHECKPOINT_CLOCK_HOST)) {
+            goto out;
+        }
+    case QEMU_CLOCK_VIRTUAL_RT:
+        if ((replay_mode != REPLAY_MODE_NONE && !runstate_is_running())
+            || !replay_checkpoint(CHECKPOINT_CLOCK_VIRTUAL_RT)) {
+            goto out;
+        }
+        break;
+    }
+
     current_time = qemu_clock_get_ns(timer_list->clock->type);
     for(;;) {
         qemu_mutex_lock(&timer_list->active_timers_lock);
@@ -545,11 +568,18 @@ 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;
diff --git a/replay/replay-internal.h b/replay/replay-internal.h
index 92d4749..f758371 100755
--- a/replay/replay-internal.h
+++ b/replay/replay-internal.h
@@ -29,6 +29,10 @@ enum ReplayEvents {
     /* some of grteater codes are reserved for clocks */
     EVENT_CLOCK,
     EVENT_CLOCK_LAST = EVENT_CLOCK + REPLAY_CLOCK_COUNT - 1,
+    /* for checkpoint event */
+    /* some of grteater codes are reserved for checkpoints */
+    EVENT_CHECKPOINT,
+    EVENT_CHECKPOINT_LAST = EVENT_CHECKPOINT + CHECKPOINT_COUNT - 1,
     EVENT_COUNT
 };
 
diff --git a/replay/replay.c b/replay/replay.c
index 5c3a8c9..e5c61c4 100755
--- a/replay/replay.c
+++ b/replay/replay.c
@@ -158,3 +158,37 @@ void replay_shutdown_request(void)
         replay_mutex_unlock();
     }
 }
+
+bool replay_checkpoint(ReplayCheckpoint checkpoint)
+{
+    bool res = false;
+    assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);
+    replay_save_instructions();
+
+    if (!replay_file) {
+        return true;
+    }
+
+    replay_mutex_lock();
+
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
+            replay_finish_event();
+        } else if (replay_data_kind != EVENT_ASYNC) {
+            res = false;
+            goto out;
+        }
+        replay_read_events(checkpoint);
+        /* replay_read_events may leave some unread events.
+           Return false if not all of the events associated with
+           checkpoint were processed */
+        res = replay_data_kind != EVENT_ASYNC;
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        replay_put_event(EVENT_CHECKPOINT + checkpoint);
+        replay_save_events(checkpoint);
+        res = true;
+    }
+out:
+    replay_mutex_unlock();
+    return res;
+}
diff --git a/replay/replay.h b/replay/replay.h
index fcc93d1..b6c4a8d 100755
--- a/replay/replay.h
+++ b/replay/replay.h
@@ -26,6 +26,19 @@ enum ReplayClockKind {
 };
 typedef enum ReplayClockKind ReplayClockKind;
 
+/* IDs of the checkpoints */
+enum ReplayCheckpoint {
+    CHECKPOINT_CLOCK_WARP,
+    CHECKPOINT_RESET_REQUESTED,
+    CHECKPOINT_CLOCK_VIRTUAL,
+    CHECKPOINT_CLOCK_HOST,
+    CHECKPOINT_CLOCK_VIRTUAL_RT,
+    CHECKPOINT_INIT,
+    CHECKPOINT_RESET,
+    CHECKPOINT_COUNT
+};
+typedef enum ReplayCheckpoint ReplayCheckpoint;
+
 extern ReplayMode replay_mode;
 
 /* Processing the instructions */
@@ -70,6 +83,12 @@ int64_t replay_read_clock(ReplayClockKind kind);
 
 /*! 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 78b1c4a..9c5c39e 100644
--- a/vl.c
+++ b/vl.c
@@ -119,6 +119,7 @@ int main(int argc, char **argv)
 #include "qapi/opts-visitor.h"
 #include "qom/object_interfaces.h"
 #include "qapi-event.h"
+#include "replay/replay.h"
 
 #define DEFAULT_RAM_SIZE 128
 
@@ -1757,7 +1758,9 @@ 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);
@@ -4216,6 +4219,10 @@ int main(int argc, char **argv, char **envp)
     }
     qemu_add_globals();
 
+    /* This checkpoint is required by replay to separate prior clock
+       reading from the other reads, because timer polling functions query
+       clock values from the log. */
+    replay_checkpoint(CHECKPOINT_INIT);
     qdev_machine_init();
 
     current_machine->ram_size = ram_size;
@@ -4325,6 +4332,10 @@ int main(int argc, char **argv, char **envp)
     /* Done notifiers can load ROMs */
     rom_load_done();
 
+    /* This checkpoint is required by replay to separate prior clock
+       reading from the other reads, because timer polling functions query
+       clock values from the log. */
+    replay_checkpoint(CHECKPOINT_RESET);
     qemu_system_reset(VMRESET_SILENT);
     if (loadvm) {
         if (load_vmstate(loadvm) < 0) {