linux-kernel - Re: [PATCH v3 11/13] perf tools: improve IBS error handling

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Date:   Wed, 1 Dec 2021 12:40:49 -0800
From:   Stephane Eranian <eranian@...gle.com>
To:     Kim Phillips <kim.phillips@....com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        acme@...hat.com, jolsa@...hat.com, songliubraving@...com,
        mpe@...erman.id.au, maddy@...ux.ibm.com
Subject: Re: [PATCH v3 11/13] perf tools: improve IBS error handling

Kim,

Could you send me the patch you want to integrate in the series. I
thought I had integrated the change in V3.


On Wed, Dec 1, 2021 at 7:30 AM Kim Phillips <kim.phillips@....com> wrote:
>
> Hi Stephane,
>
> This v3 looks like it's the same as in the v1 of the series,
> which got nacked by acme.
>
> Please use the newer patches provided.  Instructions to do
> so haven't changed since then.
>
> Thanks,
>
> Kim
>
> On 11/30/21 7:02 PM, Stephane Eranian wrote:
> > From: Kim Phillips <kim.phillips@....com>
> >
> > This patch improves the error message returned on failed perf_event_open() on
> > AMD when using IBS.
> >
> > Signed-off-by: Kim Phillips <kim.phillips@....com>
> > ---
> >   tools/perf/util/evsel.c | 42 +++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 42 insertions(+)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index ac0127be0459..39e9063c0a80 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -2852,12 +2852,52 @@ static bool find_process(const char *name)
> >       return ret ? false : true;
> >   }
> >
> > +static bool is_amd;
> > +
> > +static char *fgrep(FILE *inf, const char *str)
> > +{
> > +     char line[256];
> > +     int slen = strlen(str);
> > +
> > +     while (!feof(inf)) {
> > +             if (!fgets(line, 256, inf))
> > +                     break;
> > +             if (strncmp(line, str, slen))
> > +                     continue;
> > +
> > +             return strdup(line);
> > +     }
> > +
> > +     return NULL;
> > +}
> > +
> > +static void detect_amd(void)
> > +{
> > +     FILE *inf = fopen("/proc/cpuinfo", "r");
> > +     char *res;
> > +
> > +     if (!inf)
> > +             return;
> > +
> > +     res = fgrep(inf, "vendor_id");
> > +
> > +     if (res) {
> > +             char *s = strchr(res, ':');
> > +
> > +             is_amd = s && !strcmp(s, ": AuthenticAMD\n");
> > +             free(res);
> > +     }
> > +     fclose(inf);
> > +}
> > +
> >   int evsel__open_strerror(struct evsel *evsel, struct target *target,
> >                        int err, char *msg, size_t size)
> >   {
> >       char sbuf[STRERR_BUFSIZE];
> >       int printed = 0, enforced = 0;
> >
> > +     detect_amd();
> > +
> >       switch (err) {
> >       case EPERM:
> >       case EACCES:
> > @@ -2950,6 +2990,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
> >                       return scnprintf(msg, size, "wrong clockid (%d).", clockid);
> >               if (perf_missing_features.aux_output)
> >                       return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
> > +             if (is_amd && (evsel->core.attr.precise_ip || !strncmp(evsel->pmu_name, "ibs", 3)) && (evsel->core.attr.exclude_kernel))
> > +                     return scnprintf(msg, size, "AMD IBS can't exclude kernel events.  Try running at a higher privilege level.");
> >               break;
> >       case ENODATA:
> >               return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
> >