Pavel Dovgalyuk <pavel.dovga...@ispras.ru> writes:
> This patch introduces replay_break qmp and hmp commands.
> These commands allow stopping at the specified instruction.
> It may be useful for debugging when there are some known
> events that should be investigated.
> The commands have one argument - number of instructions
> executed since the start of the replay.
>
> Signed-off-by: Pavel Dovgalyuk <pavel.dovga...@ispras.ru>
>
> --
>
> v2:
> - renamed replay_break qmp command into replay-break
> (suggested by Eric Blake)
> ---
> hmp-commands.hx | 15 ++++++++++++
> hmp.h | 1 +
> include/sysemu/replay.h | 3 ++
> qapi/misc.json | 17 ++++++++++++++
> replay/replay-debugging.c | 55
> +++++++++++++++++++++++++++++++++++++++++++++
> replay/replay-internal.h | 4 +++
> replay/replay.c | 17 ++++++++++++++
> 7 files changed, 112 insertions(+)
>
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index db0c681..aa0794e 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1888,6 +1888,21 @@ Set QOM property @var{property} of object at location
> @var{path} to value @var{v
> ETEXI
>
> {
> + .name = "replay_break",
> + .args_type = "step:i",
> + .params = "step",
> + .help = "sets breakpoint on the specified step of the replay",
> + .cmd = hmp_replay_break,
> + },
> +
> +STEXI
> +@item replay_break @var{step}
> +@findex replay_break
> +Set breakpoint on the specified step of the replay.
> +Execution stops when the specified step is reached.
> +ETEXI
> +
> + {
> .name = "info",
> .args_type = "item:s?",
> .params = "[subcommand]",
> diff --git a/hmp.h b/hmp.h
> index d792149..ad94abe 100644
> --- a/hmp.h
> +++ b/hmp.h
> @@ -149,5 +149,6 @@ void hmp_info_vm_generation_id(Monitor *mon, const QDict
> *qdict);
> void hmp_info_memory_size_summary(Monitor *mon, const QDict *qdict);
> void hmp_info_sev(Monitor *mon, const QDict *qdict);
> void hmp_info_replay(Monitor *mon, const QDict *qdict);
> +void hmp_replay_break(Monitor *mon, const QDict *qdict);
>
> #endif
> diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
> index a5510f2..c9ba75a 100644
> --- a/include/sysemu/replay.h
> +++ b/include/sysemu/replay.h
> @@ -73,6 +73,9 @@ void replay_finish(void);
> void replay_add_blocker(Error *reason);
> /*! Returns name of the replay log file */
> const char *replay_get_filename(void);
> +/*! Sets breakpoint at the specified step.
> + If step = -1LL the existing breakpoint is removed. */
> +void replay_break(int64_t step, QEMUTimerCB callback, void *opaque);
>
> /* Processing the instructions */
>
> diff --git a/qapi/misc.json b/qapi/misc.json
> index e246ce3..4fcd211 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -3135,6 +3135,23 @@
> 'returns': 'ReplayInfo' }
>
> ##
> +# @replay-break:
> +#
> +# Set breakpoint on the specified step of the replay.
> +# Execution stops when the specified step is reached.
> +#
> +# @step: execution step to stop at
> +#
> +# Since: 3.1
> +#
> +# Example:
> +#
> +# -> { "execute": "replay-break", "data": { "step": 220414 } }
> +#
> +##
> +{ 'command': 'replay-break', 'data': { 'step': 'int' } }
> +
> +##
> # @xen-load-devices-state:
> #
> # Load the state of all devices from file. The RAM and the block devices
> diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
> index 2d364fa..c6b80c0 100644
> --- a/replay/replay-debugging.c
> +++ b/replay/replay-debugging.c
> @@ -16,6 +16,8 @@
> #include "hmp.h"
> #include "monitor/monitor.h"
> #include "qapi/qapi-commands-misc.h"
> +#include "qapi/qmp/qdict.h"
> +#include "qemu/timer.h"
>
> void hmp_info_replay(Monitor *mon, const QDict *qdict)
> {
> @@ -39,3 +41,56 @@ ReplayInfo *qmp_query_replay(Error **errp)
> retval->step = replay_get_current_step();
> return retval;
> }
> +
> +void replay_break(int64_t step, QEMUTimerCB callback, void *opaque)
> +{
> + assert(replay_mode == REPLAY_MODE_PLAY);
> + assert(replay_mutex_locked());
> +
> + replay_break_step = step;
> + if (replay_break_timer) {
> + timer_del(replay_break_timer);
> + timer_free(replay_break_timer);
> + replay_break_timer = NULL;
> + }
> +
> + if (replay_break_step == -1LL) {
> + return;
> + }
> + assert(replay_break_step >= replay_get_current_step());
> + assert(callback);
> +
> + replay_break_timer = timer_new_ns(QEMU_CLOCK_REALTIME, callback, opaque);
> +}
This function multiplexes
(a) deleting the breakpoint: @step is -1, @callback and @opaque are
ignored
(b) setting the breakpoint: step must be >= replay_get_current_step()
(which implies it's not -1), @callback must be non-null
I hate such multiplexing. I'd be more willing to tolerate it for a
static function. Why isn't it static? I can't see uses outside this
file...
To avoid the multiplexing, you could duplicate the function, specialize
both copies, then factor out the common code into a helper function.
> +
> +static void replay_stop_vm(void *opaque)
> +{
> + vm_stop(RUN_STATE_PAUSED);
> + replay_break(-1LL, NULL, NULL);
> +}
> +
> +void qmp_replay_break(int64_t step, Error **errp)
> +{
> + if (replay_mode == REPLAY_MODE_PLAY) {
> + if (step >= replay_get_current_step()) {
Pardon another ignorant question: what ensures replay_get_current_step()
stays put until we completed setting the breakpoint?
> + replay_break(step, replay_stop_vm, NULL);
> + } else {
> + error_setg(errp, "cannot set break at the step in the past");
> + }
Duplicates the >= replay_get_current_step() check we just saw in
replay_break(). Consider
if (replay_mode == REPLAY_MODE_PLAY) {
replay_break(step, replay_stop_vm, NULL, errp);
and setting an error in replay_break(). Suggestion, not demand.
> + } else {
> + error_setg(errp, "setting the break is allowed only in play mode");
s/the break/the breakpoint/
> + }
> +}
> +
> +void hmp_replay_break(Monitor *mon, const QDict *qdict)
> +{
> + int64_t step = qdict_get_try_int(qdict, "step", -1LL);
> + Error *err = NULL;
> +
> + qmp_replay_break(step, &err);
> + if (err) {
> + monitor_printf(mon, "replay_break error: %s\n",
> error_get_pretty(err));
> + error_free(err);
There's no need for the "replay_break error: " prefix; the user already
knows what command he just issued. Thus:
error_report_err(err)
> + return;
> + }
> +}
> diff --git a/replay/replay-internal.h b/replay/replay-internal.h
> index 4f82676..f9cad9d 100644
> --- a/replay/replay-internal.h
> +++ b/replay/replay-internal.h
> @@ -91,6 +91,10 @@ extern ReplayState replay_state;
>
> /* File for replay writing */
> extern FILE *replay_file;
> +/*! Step of the replay breakpoint */
Why the bang?
> +extern int64_t replay_break_step;
> +/*! Timer for the replay breakpoint callback */
Likewise.
> +extern QEMUTimer *replay_break_timer;
>
> void replay_put_byte(uint8_t byte);
> void replay_put_event(uint8_t event);
[...]
