linux-kernel - Re: [PATCH 32/35] perf intel-pt: Determine guest thread from guest sideband

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Message-ID: <CAP-5=fWRH0wUfsUA+=s8BFJLycth+xopfM-miyk0EPe+rUwoJw@mail.gmail.com>
Date:   Tue, 19 Jul 2022 18:15:52 -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 32/35] perf intel-pt: Determine guest thread from guest sideband

On Mon, Jul 11, 2022 at 2:34 AM Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> Prior to decoding, determine what guest thread, if any, is running.
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

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

Thanks,
Ian

> ---
>  tools/perf/util/intel-pt.c | 69 ++++++++++++++++++++++++++++++++++++--
>  1 file changed, 67 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
> index dc2af64f9e31..a08c2f059d5a 100644
> --- a/tools/perf/util/intel-pt.c
> +++ b/tools/perf/util/intel-pt.c
> @@ -196,6 +196,10 @@ struct intel_pt_queue {
>         struct machine *guest_machine;
>         struct thread *guest_thread;
>         struct thread *unknown_guest_thread;
> +       pid_t guest_machine_pid;
> +       pid_t guest_pid;
> +       pid_t guest_tid;
> +       int vcpu;
>         bool exclude_kernel;
>         bool have_sample;
>         u64 time;
> @@ -759,8 +763,13 @@ static int intel_pt_walk_next_insn(struct intel_pt_insn *intel_pt_insn,
>         cpumode = intel_pt_nr_cpumode(ptq, *ip, nr);
>
>         if (nr) {
> -               if ((!symbol_conf.guest_code && cpumode != PERF_RECORD_MISC_GUEST_KERNEL) ||
> -                   intel_pt_get_guest(ptq)) {
> +               if (ptq->pt->have_guest_sideband) {
> +                       if (!ptq->guest_machine || ptq->guest_machine_pid != ptq->pid) {
> +                               intel_pt_log("ERROR: guest sideband but no guest machine\n");
> +                               return -EINVAL;
> +                       }
> +               } else if ((!symbol_conf.guest_code && cpumode != PERF_RECORD_MISC_GUEST_KERNEL) ||
> +                          intel_pt_get_guest(ptq)) {
>                         intel_pt_log("ERROR: no guest machine\n");
>                         return -EINVAL;
>                 }
> @@ -1385,6 +1394,55 @@ static void intel_pt_first_timestamp(struct intel_pt *pt, u64 timestamp)
>         }
>  }
>
> +static int intel_pt_get_guest_from_sideband(struct intel_pt_queue *ptq)
> +{
> +       struct machines *machines = &ptq->pt->session->machines;
> +       struct machine *machine;
> +       pid_t machine_pid = ptq->pid;
> +       pid_t tid;
> +       int vcpu;
> +
> +       if (machine_pid <= 0)
> +               return 0; /* Not a guest machine */
> +
> +       machine = machines__find(machines, machine_pid);
> +       if (!machine)
> +               return 0; /* Not a guest machine */
> +
> +       if (ptq->guest_machine != machine) {
> +               ptq->guest_machine = NULL;
> +               thread__zput(ptq->guest_thread);
> +               thread__zput(ptq->unknown_guest_thread);
> +
> +               ptq->unknown_guest_thread = machine__find_thread(machine, 0, 0);
> +               if (!ptq->unknown_guest_thread)
> +                       return -1;
> +               ptq->guest_machine = machine;
> +       }
> +
> +       vcpu = ptq->thread ? ptq->thread->guest_cpu : -1;
> +       if (vcpu < 0)
> +               return -1;
> +
> +       tid = machine__get_current_tid(machine, vcpu);
> +
> +       if (ptq->guest_thread && ptq->guest_thread->tid != tid)
> +               thread__zput(ptq->guest_thread);
> +
> +       if (!ptq->guest_thread) {
> +               ptq->guest_thread = machine__find_thread(machine, -1, tid);
> +               if (!ptq->guest_thread)
> +                       return -1;
> +       }
> +
> +       ptq->guest_machine_pid = machine_pid;
> +       ptq->guest_pid = ptq->guest_thread->pid_;
> +       ptq->guest_tid = tid;
> +       ptq->vcpu = vcpu;
> +
> +       return 0;
> +}
> +
>  static void intel_pt_set_pid_tid_cpu(struct intel_pt *pt,
>                                      struct auxtrace_queue *queue)
>  {
> @@ -1405,6 +1463,13 @@ static void intel_pt_set_pid_tid_cpu(struct intel_pt *pt,
>                 if (queue->cpu == -1)
>                         ptq->cpu = ptq->thread->cpu;
>         }
> +
> +       if (pt->have_guest_sideband && intel_pt_get_guest_from_sideband(ptq)) {
> +               ptq->guest_machine_pid = 0;
> +               ptq->guest_pid = -1;
> +               ptq->guest_tid = -1;
> +               ptq->vcpu = -1;
> +       }
>  }
>
>  static void intel_pt_sample_flags(struct intel_pt_queue *ptq)
> --
> 2.25.1
>