Nicholas Piggin <npig...@gmail.com> writes:
> When replaying a trace, it is possible to go from shutdown to running
> with a reverse-debugging step. This can be useful if the problem being
> debugged triggers a reset or shutdown.
>
> This can be tested by making a recording of a machine that shuts down,
> then using -action shutdown=pause when replaying it. Continuing to the
> end of the trace then reverse-stepping in gdb crashes due to invalid
> runstate transition.
>
> Just permitting the transition seems to be all that's necessary for
> reverse-debugging to work well in such a state.
>
> Reviewed-by: Pavel Dovgalyuk <pavel.dovgal...@ispras.ru>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
> ---
> include/sysemu/runstate.h | 1 +
> replay/replay.c | 2 ++
> system/runstate.c | 19 +++++++++++++++++++
> 3 files changed, 22 insertions(+)
>
> diff --git a/include/sysemu/runstate.h b/include/sysemu/runstate.h
> index 0117d243c4..fe25eed3c0 100644
> --- a/include/sysemu/runstate.h
> +++ b/include/sysemu/runstate.h
> @@ -9,6 +9,7 @@ void runstate_set(RunState new_state);
> RunState runstate_get(void);
> bool runstate_is_running(void);
> bool runstate_needs_reset(void);
> +void runstate_replay_enable(void);
>
> typedef void VMChangeStateHandler(void *opaque, bool running, RunState
> state);
>
> diff --git a/replay/replay.c b/replay/replay.c
> index 3fd241a4fc..2951eed3bd 100644
> --- a/replay/replay.c
> +++ b/replay/replay.c
> @@ -383,6 +383,8 @@ static void replay_enable(const char *fname, int mode)
> /* go to the beginning */
> fseek(replay_file, HEADER_SIZE, SEEK_SET);
> replay_fetch_data_kind();
> +
> + runstate_replay_enable();
> }
>
> replay_init_events();
> diff --git a/system/runstate.c b/system/runstate.c
> index d6ab860eca..bd0fed8657 100644
> --- a/system/runstate.c
> +++ b/system/runstate.c
> @@ -182,6 +182,12 @@ static const RunStateTransition
> runstate_transitions_def[] = {
> { RUN_STATE__MAX, RUN_STATE__MAX },
> };
>
> +static const RunStateTransition replay_runstate_transitions_def[] = {
> + { RUN_STATE_SHUTDOWN, RUN_STATE_RUNNING},
> +
> + { RUN_STATE__MAX, RUN_STATE__MAX },
> +};
> +
> static bool runstate_valid_transitions[RUN_STATE__MAX][RUN_STATE__MAX];
>
> bool runstate_check(RunState state)
> @@ -189,6 +195,19 @@ bool runstate_check(RunState state)
> return current_run_state == state;
> }
>
> +void runstate_replay_enable(void)
> +{
> + const RunStateTransition *p;
> +
> + assert(replay_mode == REPLAY_MODE_PLAY);
> +
As the bellow is common to runstate_init it could be
re-factored into a helper taking the runstate_transitions_def pointer.
> + for (p = &replay_runstate_transitions_def[0]; p->from != RUN_STATE__MAX;
> + p++) {
> + runstate_valid_transitions[p->from][p->to] = true;
> + }
> +
> +}
> +
> static void runstate_init(void)
> {
> const RunStateTransition *p;
--
Alex Bennée
Virtualisation Tech Lead @ Linaro
