Hi Alex,
January 9, 2025 at 3:04 PM, "Alex Bennée" wrote:
> Julian Ganz <neither@nut.email> writes:
> > We recently introduced new plugin API for registration of discontinuity
> > related callbacks. This change introduces a minimal plugin showcasing
> > the new API. It simply counts the occurances of interrupts, exceptions
> > and host calls per CPU and reports the counts when exitting.
> > ---
> > contrib/plugins/meson.build | 3 +-
> > contrib/plugins/traps.c | 96 +++++++++++++++++++++++++++++++++++++
> > 2 files changed, 98 insertions(+), 1 deletion(-)
> > create mode 100644 contrib/plugins/traps.c
> >
> > diff --git a/contrib/plugins/meson.build b/contrib/plugins/meson.build
> > index 63a32c2b4f..9a3015e1c1 100644
> > --- a/contrib/plugins/meson.build
> > +++ b/contrib/plugins/meson.build
> > @@ -1,5 +1,6 @@
> > contrib_plugins = ['bbv', 'cache', 'cflow', 'drcov', 'execlog',
> > 'hotblocks',
> > - 'hotpages', 'howvec', 'hwprofile', 'ips', 'stoptrigger']
> > + 'hotpages', 'howvec', 'hwprofile', 'ips', 'stoptrigger',
> > + 'traps']
> >
> I wonder if this is better in tests/tcg/plugins? We need to do something
> to ensure it gets covered by CI although we might want to be smarter
> about running it together with a test binary that will actually pick up
> something.
The callback is intended as an example. The patch-series does contain a
dedicated testing plugin. And iirc the contrib plugins are now built
with the rest of qemu anyway?
> > +QEMU_PLUGIN_EXPORT
> > +int qemu_plugin_install(qemu_plugin_id_t id, const qemu_info_t *info,
> > + int argc, char **argv)
> > +{
> > + if (!info->system_emulation) {
> > + fputs("trap plugin can only be used in system emulation mode.\n",
> > + stderr);
> > + return -1;
> > + }
> > +
> > + max_vcpus = info->system.max_vcpus;
> > + traps = qemu_plugin_scoreboard_new(sizeof(TrapCounters));
> > + qemu_plugin_register_vcpu_init_cb(id, vcpu_init);
> > + qemu_plugin_vcpu_for_each(id, vcpu_init);
> >
> Hmm at first glances this seems redundant - however I guess this is
> covering the use case you load the plugin after the system is up and
> running.
Yep, but really that was just me being paranoid.
> I wonder if you have unearthed a foot-gun in the API that is easy to
> fall into? Maybe we should expand qemu_plugin_register_vcpu_init_cb to
> call the call back immediately for existing vcpus?
Would probably not hurt.
Regards,
Julian
