replay: recording and replaying clock ticks

Clock ticks are considered as the sources of non-deterministic data for
virtual machine. This patch implements saving the clock values when they
are acquired (virtual, host clock).
When replaying the execution corresponding values are read from log and
transfered to the module, which wants to read the values.
Such a design required the clock polling to be synchronized. Sometimes
it is not true - e.g. when timeouts for timer lists are checked. In this case
we use a cached value of the clock, passing it to the client code.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20150917162427.8676.36558.stgit@PASHA-ISP.def.inno>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>

1 files changed, 11 insertions, 0 deletions

diff --git a/replay/replay-internal.h b/replay/replay-internal.h
index 23807ca..f042c46 100644
--- a/replay/replay-internal.h
+++ b/replay/replay-internal.h
@@ -23,6 +23,10 @@ enum ReplayEvents {
     EVENT_EXCEPTION,
     /* for async events */
     EVENT_ASYNC,
+    /* for clock read/writes */
+    /* some of greater codes are reserved for clocks */
+    EVENT_CLOCK,
+    EVENT_CLOCK_LAST = EVENT_CLOCK + REPLAY_CLOCK_COUNT - 1,
     EVENT_COUNT
 };
 
@@ -35,6 +39,8 @@ enum ReplayAsyncEventKind {
 typedef enum ReplayAsyncEventKind ReplayAsyncEventKind;
 
 typedef struct ReplayState {
+    /*! Cached clock values. */
+    int64_t cached_clock[REPLAY_CLOCK_COUNT];
     /*! Current step - number of processed instructions and timer events. */
     uint64_t current_step;
     /*! Number of instructions to be executed before other events happen. */
@@ -85,6 +91,11 @@ void replay_save_instructions(void);
     \return true, if event was found */
 bool replay_next_event_is(int event);
 
+/*! Reads next clock value from the file.
+    If clock kind read from the file is different from the parameter,
+    the value is not used. */
+void replay_read_next_clock(unsigned int kind);
+
 /* Asynchronous events queue */
 
 /*! Initializes events' processing internals */