replay: allow loading any snapshots before recording

This patch enables using -loadvm in recording mode to allow starting
the execution recording from any of the available snapshots.
It also fixes loading of the record/replay state, therefore snapshots
created in replay mode may also be used for starting the new recording.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
Message-Id: <20180912081939.3228.56131.stgit@pasha-VirtualBox>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

2 files changed, 16 insertions, 8 deletions

diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c
index 2ab85cfc60..16bacc98bc 100644
--- a/replay/replay-snapshot.c
+++ b/replay/replay-snapshot.c
@@ -33,11 +33,18 @@ static int replay_pre_save(void *opaque)
 static int replay_post_load(void *opaque, int version_id)
 {
     ReplayState *state = opaque;
-    fseek(replay_file, state->file_offset, SEEK_SET);
-    qemu_clock_set_last(QEMU_CLOCK_HOST, state->host_clock_last);
-    /* If this was a vmstate, saved in recording mode,
-       we need to initialize replay data fields. */
-    replay_fetch_data_kind();
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        fseek(replay_file, state->file_offset, SEEK_SET);
+        qemu_clock_set_last(QEMU_CLOCK_HOST, state->host_clock_last);
+        /* If this was a vmstate, saved in recording mode,
+           we need to initialize replay data fields. */
+        replay_fetch_data_kind();
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        /* This is only useful for loading the initial state.
+           Therefore reset all the counters. */
+        state->instructions_count = 0;
+        state->block_request_id = 0;
+    }
 
     return 0;
 }
diff --git a/vl.c b/vl.c
index f2964d9e43..0388852deb 100644
--- a/vl.c
+++ b/vl.c
@@ -4535,9 +4535,7 @@ int main(int argc, char **argv, char **envp)
     replay_checkpoint(CHECKPOINT_RESET);
     qemu_system_reset(SHUTDOWN_CAUSE_NONE);
     register_global_state();
-    if (replay_mode != REPLAY_MODE_NONE) {
-        replay_vmstate_init();
-    } else if (loadvm) {
+    if (loadvm) {
         Error *local_err = NULL;
         if (load_snapshot(loadvm, &local_err) < 0) {
             error_report_err(local_err);
@@ -4545,6 +4543,9 @@ int main(int argc, char **argv, char **envp)
             exit(1);
         }
     }
+    if (replay_mode != REPLAY_MODE_NONE) {
+        replay_vmstate_init();
+    }
 
     qdev_prop_check_globals();
     if (vmstate_dump_file) {