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, 64 insertions, 0 deletions

diff --git a/replay/replay-time.c b/replay/replay-time.c
new file mode 100644
index 0000000000..6d06951f5e
--- /dev/null
+++ b/replay/replay-time.c
@@ -0,0 +1,64 @@
+/*
+ * replay-time.c
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "qemu/error-report.h"
+
+int64_t replay_save_clock(ReplayClockKind kind, int64_t clock)
+{
+    replay_save_instructions();
+
+    if (replay_file) {
+        replay_mutex_lock();
+        replay_put_event(EVENT_CLOCK + kind);
+        replay_put_qword(clock);
+        replay_mutex_unlock();
+    }
+
+    return clock;
+}
+
+void replay_read_next_clock(ReplayClockKind kind)
+{
+    unsigned int read_kind = replay_data_kind - EVENT_CLOCK;
+
+    assert(read_kind == kind);
+
+    int64_t clock = replay_get_qword();
+
+    replay_check_error();
+    replay_finish_event();
+
+    replay_state.cached_clock[read_kind] = clock;
+}
+
+/*! Reads next clock event from the input. */
+int64_t replay_read_clock(ReplayClockKind kind)
+{
+    replay_account_executed_instructions();
+
+    if (replay_file) {
+        int64_t ret;
+        replay_mutex_lock();
+        if (replay_next_event_is(EVENT_CLOCK + kind)) {
+            replay_read_next_clock(kind);
+        }
+        ret = replay_state.cached_clock[kind];
+        replay_mutex_unlock();
+
+        return ret;
+    }
+
+    error_report("REPLAY INTERNAL ERROR %d", __LINE__);
+    exit(1);
+}