linux-kernel - Re: [PATCH 30/35] perf intel-pt: Track guest context switches

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Date:   Tue, 19 Jul 2022 18:13:54 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 30/35] perf intel-pt: Track guest context switches

On Mon, Jul 11, 2022 at 2:33 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Use guest context switch events to keep track of which guest thread is
> running on a particular guest machine and VCPU.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

Acked-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/util/intel-pt.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index a8798b5bb311..98b097fec476 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -78,6 +78,7 @@ struct intel_pt {
>         bool use_thread_stack;
>         bool callstack;
>         bool cap_event_trace;
> +       bool have_guest_sideband;
>         unsigned int br_stack_sz;
>         unsigned int br_stack_sz_plus;
>         int have_sched_switch;
> @@ -3079,6 +3080,25 @@ static int intel_pt_context_switch_in(struct intel_pt *pt,
>         return machine__set_current_tid(pt->machine, cpu, pid, tid);
>  }
>
> +static int intel_pt_guest_context_switch(struct intel_pt *pt,
> +                                        union perf_event *event,
> +                                        struct perf_sample *sample)
> +{
> +       bool out = event->header.misc & PERF_RECORD_MISC_SWITCH_OUT;
> +       struct machines *machines = &pt->session->machines;
> +       struct machine *machine = machines__find(machines, sample->machine_pid);
> +
> +       pt->have_guest_sideband = true;
> +
> +       if (out)
> +               return 0;
> +
> +       if (!machine)
> +               return -EINVAL;
> +
> +       return machine__set_current_tid(machine, sample->vcpu, sample->pid, sample->tid);
> +}
> +
>  static int intel_pt_context_switch(struct intel_pt *pt, union perf_event *event,
>                                    struct perf_sample *sample)
>  {
> @@ -3086,6 +3106,9 @@ static int intel_pt_context_switch(struct intel_pt *pt, union perf_event *event,
>         pid_t pid, tid;
>         int cpu, ret;
>
> +       if (perf_event__is_guest(event))
> +               return intel_pt_guest_context_switch(pt, event, sample);
> +
>         cpu = sample->cpu;
>
>         if (pt->have_sched_switch == 3) {
> --
> 2.25.1
>