> From: Markus Armbruster [mailto:arm...@redhat.com]
> 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.
Thanks, I'll split this into two functions.
>
> > +
> > +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?
In icount mode iothread and vcpu thread use the replay mutex for
serializing their operations. Therefore such races are impossible.
>
> > + 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)
Ok.
> > + 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?
This is a doxygen-style comment for automatic documentation generation.
Pavel Dovgalyuk
