The perf_event_open might fail due to various reasons, so blindly
reducing precise_ip level might not be the best way to deal with it.

It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
given precise level.  Let's try again with the correct error code.

This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
user events with exclude_kernel=1 cannot make progress.  Let's add the
evsel__handle_error_quirks() to this case specially.  I plan to work on
the kernel side to improve this situation but it'd still need some
special handling for IBS.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 32e30c293d0c6198..ef8356260eea54cd 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
 	return false;
 }
 
+static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
+{
+	/* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
+	if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
+	    evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
+		evsel->core.attr.precise_ip = 0;
+		pr_debug2_peo("removing precise_ip on AMD\n");
+		display_attr(&evsel->core.attr);
+		return true;
+	}
+
+	return false;
+}
+
 static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		struct perf_thread_map *threads,
 		int start_cpu_map_idx, int end_cpu_map_idx)
@@ -2580,9 +2594,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	return 0;
 
 try_fallback:
-	if (evsel__precise_ip_fallback(evsel))
-		goto retry_open;
-
 	if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
 					 idx, threads, thread, err)) {
 		/* We just removed 1 thread, so lower the upper nthreads limit. */
@@ -2599,11 +2610,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
 		goto retry_open;
 
-	if (err != -EINVAL || idx > 0 || thread > 0)
-		goto out_close;
+	if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
+		goto retry_open;
 
-	if (evsel__detect_missing_features(evsel))
+	if (err == -EINVAL && evsel__detect_missing_features(evsel))
 		goto fallback_missing_features;
+
+	if (evsel__handle_error_quirks(evsel, err))
+		goto retry_open;
+
 out_close:
 	if (err)
 		threads->err_thread = thread;
-- 
2.46.1.824.gd892dcdcdd-goog

On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> The perf_event_open might fail due to various reasons, so blindly
> reducing precise_ip level might not be the best way to deal with it.
>
> It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> given precise level.  Let's try again with the correct error code.
>
> This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> user events with exclude_kernel=1 cannot make progress.  Let's add the
> evsel__handle_error_quirks() to this case specially.  I plan to work on
> the kernel side to improve this situation but it'd still need some
> special handling for IBS.
>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
>  1 file changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 32e30c293d0c6198..ef8356260eea54cd 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
>         return false;
>  }
>
> +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> +{
> +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */

Should the quirk handling be specific to evsels with the IBS PMU given
the comment above? ie this is a PMU specific workaround rather than an
AMD specific workaround, however, the PMU only exists on AMD :-)

> +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {

So here rather than x86__is_amd_cpu it would be
!strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
the logic into pmu.c.

Thanks,
Ian


> +               evsel->core.attr.precise_ip = 0;
> +               pr_debug2_peo("removing precise_ip on AMD\n");
> +               display_attr(&evsel->core.attr);
> +               return true;
> +       }
> +
> +       return false;
> +}
> +
>  static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>                 struct perf_thread_map *threads,
>                 int start_cpu_map_idx, int end_cpu_map_idx)
> @@ -2580,9 +2594,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>         return 0;
>
>  try_fallback:
> -       if (evsel__precise_ip_fallback(evsel))
> -               goto retry_open;
> -
>         if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
>                                          idx, threads, thread, err)) {
>                 /* We just removed 1 thread, so lower the upper nthreads limit. */
> @@ -2599,11 +2610,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>         if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
>                 goto retry_open;
>
> -       if (err != -EINVAL || idx > 0 || thread > 0)
> -               goto out_close;
> +       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> +               goto retry_open;
>
> -       if (evsel__detect_missing_features(evsel))
> +       if (err == -EINVAL && evsel__detect_missing_features(evsel))
>                 goto fallback_missing_features;
> +
> +       if (evsel__handle_error_quirks(evsel, err))
> +               goto retry_open;
> +
>  out_close:
>         if (err)
>                 threads->err_thread = thread;
> --
> 2.46.1.824.gd892dcdcdd-goog
>

On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > The perf_event_open might fail due to various reasons, so blindly
> > reducing precise_ip level might not be the best way to deal with it.
> >
> > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > given precise level.  Let's try again with the correct error code.
> >
> > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > the kernel side to improve this situation but it'd still need some
> > special handling for IBS.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> >  1 file changed, 21 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > --- a/tools/perf/util/evsel.c
> > +++ b/tools/perf/util/evsel.c
> > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> >         return false;
> >  }
> >
> > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > +{
> > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> 
> Should the quirk handling be specific to evsels with the IBS PMU given
> the comment above? ie this is a PMU specific workaround rather than an
> AMD specific workaround, however, the PMU only exists on AMD :-)
> 
> > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> 
> So here rather than x86__is_amd_cpu it would be
> !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> the logic into pmu.c.

I guess the problem is that AMD driver does implicit forwarding to IBS
if the legacy hardware events have precise_ip.  So it might have just
core pmu (or no pmu) in the evsel.
 
Thanks,
Namhyung

> 
> > +               evsel->core.attr.precise_ip = 0;
> > +               pr_debug2_peo("removing precise_ip on AMD\n");
> > +               display_attr(&evsel->core.attr);
> > +               return true;
> > +       }
> > +
> > +       return false;
> > +}
> > +
> >  static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> >                 struct perf_thread_map *threads,
> >                 int start_cpu_map_idx, int end_cpu_map_idx)
> > @@ -2580,9 +2594,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> >         return 0;
> >
> >  try_fallback:
> > -       if (evsel__precise_ip_fallback(evsel))
> > -               goto retry_open;
> > -
> >         if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
> >                                          idx, threads, thread, err)) {
> >                 /* We just removed 1 thread, so lower the upper nthreads limit. */
> > @@ -2599,11 +2610,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> >         if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
> >                 goto retry_open;
> >
> > -       if (err != -EINVAL || idx > 0 || thread > 0)
> > -               goto out_close;
> > +       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> > +               goto retry_open;
> >
> > -       if (evsel__detect_missing_features(evsel))
> > +       if (err == -EINVAL && evsel__detect_missing_features(evsel))
> >                 goto fallback_missing_features;
> > +
> > +       if (evsel__handle_error_quirks(evsel, err))
> > +               goto retry_open;
> > +
> >  out_close:
> >         if (err)
> >                 threads->err_thread = thread;
> > --
> > 2.46.1.824.gd892dcdcdd-goog
> >

On Tue, Oct 1, 2024 at 2:36 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> > On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > >
> > > The perf_event_open might fail due to various reasons, so blindly
> > > reducing precise_ip level might not be the best way to deal with it.
> > >
> > > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > > given precise level.  Let's try again with the correct error code.
> > >
> > > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > > the kernel side to improve this situation but it'd still need some
> > > special handling for IBS.
> > >
> > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > > ---
> > >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> > >  1 file changed, 21 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > > --- a/tools/perf/util/evsel.c
> > > +++ b/tools/perf/util/evsel.c
> > > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> > >         return false;
> > >  }
> > >
> > > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > > +{
> > > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> >
> > Should the quirk handling be specific to evsels with the IBS PMU given
> > the comment above? ie this is a PMU specific workaround rather than an
> > AMD specific workaround, however, the PMU only exists on AMD :-)
> >
> > > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> >
> > So here rather than x86__is_amd_cpu it would be
> > !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> > the logic into pmu.c.
>
> I guess the problem is that AMD driver does implicit forwarding to IBS
> if the legacy hardware events have precise_ip.  So it might have just
> core pmu (or no pmu) in the evsel.

I think the no PMU case should probably have a PMU possibly similar to
the tool PMU in:
https://lore.kernel.org/all/20240912190341.919229-1-irogers@google.com/
But that's not in place yet. You can always use
perf_pmus__scan_core(NULL) or
perf_pmus__find_by_type(evsel->core.attr.type or PERF_TYPE_RAW).
evsel->pmu->is_core && x86__is_amd_cpu() would identify an AMD core
PMU whereas the code above could fire for IBS or other PMUs.

Thanks,
Ian

> >
> > > +               evsel->core.attr.precise_ip = 0;
> > > +               pr_debug2_peo("removing precise_ip on AMD\n");
> > > +               display_attr(&evsel->core.attr);
> > > +               return true;
> > > +       }
> > > +
> > > +       return false;
> > > +}
> > > +
> > >  static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > >                 struct perf_thread_map *threads,
> > >                 int start_cpu_map_idx, int end_cpu_map_idx)
> > > @@ -2580,9 +2594,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > >         return 0;
> > >
> > >  try_fallback:
> > > -       if (evsel__precise_ip_fallback(evsel))
> > > -               goto retry_open;
> > > -
> > >         if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
> > >                                          idx, threads, thread, err)) {
> > >                 /* We just removed 1 thread, so lower the upper nthreads limit. */
> > > @@ -2599,11 +2610,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > >         if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
> > >                 goto retry_open;
> > >
> > > -       if (err != -EINVAL || idx > 0 || thread > 0)
> > > -               goto out_close;
> > > +       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> > > +               goto retry_open;
> > >
> > > -       if (evsel__detect_missing_features(evsel))
> > > +       if (err == -EINVAL && evsel__detect_missing_features(evsel))
> > >                 goto fallback_missing_features;
> > > +
> > > +       if (evsel__handle_error_quirks(evsel, err))
> > > +               goto retry_open;
> > > +
> > >  out_close:
> > >         if (err)
> > >                 threads->err_thread = thread;
> > > --
> > > 2.46.1.824.gd892dcdcdd-goog
> > >

On Tue, Oct 01, 2024 at 03:21:50PM -0700, Ian Rogers wrote:
> On Tue, Oct 1, 2024 at 2:36 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> > > On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > >
> > > > The perf_event_open might fail due to various reasons, so blindly
> > > > reducing precise_ip level might not be the best way to deal with it.
> > > >
> > > > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > > > given precise level.  Let's try again with the correct error code.
> > > >
> > > > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > > > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > > > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > > > the kernel side to improve this situation but it'd still need some
> > > > special handling for IBS.
> > > >
> > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > > > ---
> > > >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> > > >  1 file changed, 21 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > > > --- a/tools/perf/util/evsel.c
> > > > +++ b/tools/perf/util/evsel.c
> > > > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> > > >         return false;
> > > >  }
> > > >
> > > > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > > > +{
> > > > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> > >
> > > Should the quirk handling be specific to evsels with the IBS PMU given
> > > the comment above? ie this is a PMU specific workaround rather than an
> > > AMD specific workaround, however, the PMU only exists on AMD :-)
> > >
> > > > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > > > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> > >
> > > So here rather than x86__is_amd_cpu it would be
> > > !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> > > the logic into pmu.c.
> >
> > I guess the problem is that AMD driver does implicit forwarding to IBS
> > if the legacy hardware events have precise_ip.  So it might have just
> > core pmu (or no pmu) in the evsel.
> 
> I think the no PMU case should probably have a PMU possibly similar to
> the tool PMU in:
> https://lore.kernel.org/all/20240912190341.919229-1-irogers@google.com/
> But that's not in place yet. You can always use
> perf_pmus__scan_core(NULL) or
> perf_pmus__find_by_type(evsel->core.attr.type or PERF_TYPE_RAW).
> evsel->pmu->is_core && x86__is_amd_cpu() would identify an AMD core
> PMU whereas the code above could fire for IBS or other PMUs.

But IBS is the only PMU on AMD that provides precise_ip IIRC.  So I
don't think other events would have it nor have any effect on changing
the value.  So maybe we can skip the PMU scanning and just drop to 0?

Thanks,
Namhyung

> 
> > >
> > > > +               evsel->core.attr.precise_ip = 0;
> > > > +               pr_debug2_peo("removing precise_ip on AMD\n");
> > > > +               display_attr(&evsel->core.attr);
> > > > +               return true;
> > > > +       }
> > > > +
> > > > +       return false;
> > > > +}
> > > > +
> > > >  static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > > >                 struct perf_thread_map *threads,
> > > >                 int start_cpu_map_idx, int end_cpu_map_idx)
> > > > @@ -2580,9 +2594,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > > >         return 0;
> > > >
> > > >  try_fallback:
> > > > -       if (evsel__precise_ip_fallback(evsel))
> > > > -               goto retry_open;
> > > > -
> > > >         if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
> > > >                                          idx, threads, thread, err)) {
> > > >                 /* We just removed 1 thread, so lower the upper nthreads limit. */
> > > > @@ -2599,11 +2610,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > > >         if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
> > > >                 goto retry_open;
> > > >
> > > > -       if (err != -EINVAL || idx > 0 || thread > 0)
> > > > -               goto out_close;
> > > > +       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> > > > +               goto retry_open;
> > > >
> > > > -       if (evsel__detect_missing_features(evsel))
> > > > +       if (err == -EINVAL && evsel__detect_missing_features(evsel))
> > > >                 goto fallback_missing_features;
> > > > +
> > > > +       if (evsel__handle_error_quirks(evsel, err))
> > > > +               goto retry_open;
> > > > +
> > > >  out_close:
> > > >         if (err)
> > > >                 threads->err_thread = thread;
> > > > --
> > > > 2.46.1.824.gd892dcdcdd-goog
> > > >

On Thu, Oct 3, 2024 at 10:06 AM Namhyung Kim <namhyung@kernel.org> wrote:
>
> On Tue, Oct 01, 2024 at 03:21:50PM -0700, Ian Rogers wrote:
> > On Tue, Oct 1, 2024 at 2:36 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > >
> > > On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> > > > On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > > >
> > > > > The perf_event_open might fail due to various reasons, so blindly
> > > > > reducing precise_ip level might not be the best way to deal with it.
> > > > >
> > > > > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > > > > given precise level.  Let's try again with the correct error code.
> > > > >
> > > > > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > > > > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > > > > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > > > > the kernel side to improve this situation but it'd still need some
> > > > > special handling for IBS.
> > > > >
> > > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > > > > ---
> > > > >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> > > > >  1 file changed, 21 insertions(+), 6 deletions(-)
> > > > >
> > > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > > > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > > > > --- a/tools/perf/util/evsel.c
> > > > > +++ b/tools/perf/util/evsel.c
> > > > > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> > > > >         return false;
> > > > >  }
> > > > >
> > > > > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > > > > +{
> > > > > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> > > >
> > > > Should the quirk handling be specific to evsels with the IBS PMU given
> > > > the comment above? ie this is a PMU specific workaround rather than an
> > > > AMD specific workaround, however, the PMU only exists on AMD :-)
> > > >
> > > > > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > > > > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> > > >
> > > > So here rather than x86__is_amd_cpu it would be
> > > > !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> > > > the logic into pmu.c.
> > >
> > > I guess the problem is that AMD driver does implicit forwarding to IBS
> > > if the legacy hardware events have precise_ip.  So it might have just
> > > core pmu (or no pmu) in the evsel.
> >
> > I think the no PMU case should probably have a PMU possibly similar to
> > the tool PMU in:
> > https://lore.kernel.org/all/20240912190341.919229-1-irogers@google.com/
> > But that's not in place yet. You can always use
> > perf_pmus__scan_core(NULL) or
> > perf_pmus__find_by_type(evsel->core.attr.type or PERF_TYPE_RAW).
> > evsel->pmu->is_core && x86__is_amd_cpu() would identify an AMD core
> > PMU whereas the code above could fire for IBS or other PMUs.
>
> But IBS is the only PMU on AMD that provides precise_ip IIRC.  So I
> don't think other events would have it nor have any effect on changing
> the value.  So maybe we can skip the PMU scanning and just drop to 0?

cpu supports precise_ip as it forwards it to IBS, IBS is an ambiguous
term as there are ibs_op and ibs_fetch PMUs. The code is using values
in the attribute to infer the PMU that is being used, it feels it
would be more intention revealing to do things like:
```
if (error == ... && perf_pmu__is_ibs_op_or_fetch(evsel->pmu)) ..
```
perhaps to not burden the code this can be:
```
if (...) {
  assert(perf_pmu__is_ibs_op_or_fetch(evsel->pmu));
```

Thanks,
Ian

> >
> > > >
> > > > > +               evsel->core.attr.precise_ip = 0;
> > > > > +               pr_debug2_peo("removing precise_ip on AMD\n");
> > > > > +               display_attr(&evsel->core.attr);
> > > > > +               return true;
> > > > > +       }
> > > > > +
> > > > > +       return false;
> > > > > +}
> > > > > +
> > > > >  static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > > > >                 struct perf_thread_map *threads,
> > > > >                 int start_cpu_map_idx, int end_cpu_map_idx)
> > > > > @@ -2580,9 +2594,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > > > >         return 0;
> > > > >
> > > > >  try_fallback:
> > > > > -       if (evsel__precise_ip_fallback(evsel))
> > > > > -               goto retry_open;
> > > > > -
> > > > >         if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
> > > > >                                          idx, threads, thread, err)) {
> > > > >                 /* We just removed 1 thread, so lower the upper nthreads limit. */
> > > > > @@ -2599,11 +2610,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> > > > >         if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
> > > > >                 goto retry_open;
> > > > >
> > > > > -       if (err != -EINVAL || idx > 0 || thread > 0)
> > > > > -               goto out_close;
> > > > > +       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> > > > > +               goto retry_open;
> > > > >
> > > > > -       if (evsel__detect_missing_features(evsel))
> > > > > +       if (err == -EINVAL && evsel__detect_missing_features(evsel))
> > > > >                 goto fallback_missing_features;
> > > > > +
> > > > > +       if (evsel__handle_error_quirks(evsel, err))
> > > > > +               goto retry_open;
> > > > > +
> > > > >  out_close:
> > > > >         if (err)
> > > > >                 threads->err_thread = thread;
> > > > > --
> > > > > 2.46.1.824.gd892dcdcdd-goog
> > > > >

On Thu, Oct 03, 2024 at 10:32:47AM -0700, Ian Rogers wrote:
> On Thu, Oct 3, 2024 at 10:06 AM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > On Tue, Oct 01, 2024 at 03:21:50PM -0700, Ian Rogers wrote:
> > > On Tue, Oct 1, 2024 at 2:36 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > >
> > > > On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> > > > > On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > > > >
> > > > > > The perf_event_open might fail due to various reasons, so blindly
> > > > > > reducing precise_ip level might not be the best way to deal with it.
> > > > > >
> > > > > > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > > > > > given precise level.  Let's try again with the correct error code.
> > > > > >
> > > > > > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > > > > > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > > > > > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > > > > > the kernel side to improve this situation but it'd still need some
> > > > > > special handling for IBS.
> > > > > >
> > > > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > > > > > ---
> > > > > >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> > > > > >  1 file changed, 21 insertions(+), 6 deletions(-)
> > > > > >
> > > > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > > > > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > > > > > --- a/tools/perf/util/evsel.c
> > > > > > +++ b/tools/perf/util/evsel.c
> > > > > > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> > > > > >         return false;
> > > > > >  }
> > > > > >
> > > > > > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > > > > > +{
> > > > > > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> > > > >
> > > > > Should the quirk handling be specific to evsels with the IBS PMU given
> > > > > the comment above? ie this is a PMU specific workaround rather than an
> > > > > AMD specific workaround, however, the PMU only exists on AMD :-)
> > > > >
> > > > > > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > > > > > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> > > > >
> > > > > So here rather than x86__is_amd_cpu it would be
> > > > > !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> > > > > the logic into pmu.c.
> > > >
> > > > I guess the problem is that AMD driver does implicit forwarding to IBS
> > > > if the legacy hardware events have precise_ip.  So it might have just
> > > > core pmu (or no pmu) in the evsel.
> > >
> > > I think the no PMU case should probably have a PMU possibly similar to
> > > the tool PMU in:
> > > https://lore.kernel.org/all/20240912190341.919229-1-irogers@google.com/
> > > But that's not in place yet. You can always use
> > > perf_pmus__scan_core(NULL) or
> > > perf_pmus__find_by_type(evsel->core.attr.type or PERF_TYPE_RAW).
> > > evsel->pmu->is_core && x86__is_amd_cpu() would identify an AMD core
> > > PMU whereas the code above could fire for IBS or other PMUs.
> >
> > But IBS is the only PMU on AMD that provides precise_ip IIRC.  So I
> > don't think other events would have it nor have any effect on changing
> > the value.  So maybe we can skip the PMU scanning and just drop to 0?
> 
> cpu supports precise_ip as it forwards it to IBS, IBS is an ambiguous
> term as there are ibs_op and ibs_fetch PMUs. The code is using values
> in the attribute to infer the PMU that is being used, it feels it
> would be more intention revealing to do things like:
> ```
> if (error == ... && perf_pmu__is_ibs_op_or_fetch(evsel->pmu)) ..
> ```

I guess it'd get a core PMU for the default cycles event.  I think the
intention is already confusing with the implicit forwarding.

Thanks,
Namhyung


> perhaps to not burden the code this can be:
> ```
> if (...) {
>   assert(perf_pmu__is_ibs_op_or_fetch(evsel->pmu));
> ```
> 
> Thanks,
> Ian

Hi Ian,

On Thu, Oct 03, 2024 at 03:38:01PM -0700, Namhyung Kim wrote:
> On Thu, Oct 03, 2024 at 10:32:47AM -0700, Ian Rogers wrote:
> > On Thu, Oct 3, 2024 at 10:06 AM Namhyung Kim <namhyung@kernel.org> wrote:
> > >
> > > On Tue, Oct 01, 2024 at 03:21:50PM -0700, Ian Rogers wrote:
> > > > On Tue, Oct 1, 2024 at 2:36 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > > >
> > > > > On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> > > > > > On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > > > > >
> > > > > > > The perf_event_open might fail due to various reasons, so blindly
> > > > > > > reducing precise_ip level might not be the best way to deal with it.
> > > > > > >
> > > > > > > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > > > > > > given precise level.  Let's try again with the correct error code.
> > > > > > >
> > > > > > > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > > > > > > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > > > > > > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > > > > > > the kernel side to improve this situation but it'd still need some
> > > > > > > special handling for IBS.
> > > > > > >
> > > > > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > > > > > > ---
> > > > > > >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> > > > > > >  1 file changed, 21 insertions(+), 6 deletions(-)
> > > > > > >
> > > > > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > > > > > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > > > > > > --- a/tools/perf/util/evsel.c
> > > > > > > +++ b/tools/perf/util/evsel.c
> > > > > > > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> > > > > > >         return false;
> > > > > > >  }
> > > > > > >
> > > > > > > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > > > > > > +{
> > > > > > > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> > > > > >
> > > > > > Should the quirk handling be specific to evsels with the IBS PMU given
> > > > > > the comment above? ie this is a PMU specific workaround rather than an
> > > > > > AMD specific workaround, however, the PMU only exists on AMD :-)
> > > > > >
> > > > > > > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > > > > > > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> > > > > >
> > > > > > So here rather than x86__is_amd_cpu it would be
> > > > > > !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> > > > > > the logic into pmu.c.
> > > > >
> > > > > I guess the problem is that AMD driver does implicit forwarding to IBS
> > > > > if the legacy hardware events have precise_ip.  So it might have just
> > > > > core pmu (or no pmu) in the evsel.
> > > >
> > > > I think the no PMU case should probably have a PMU possibly similar to
> > > > the tool PMU in:
> > > > https://lore.kernel.org/all/20240912190341.919229-1-irogers@google.com/
> > > > But that's not in place yet. You can always use
> > > > perf_pmus__scan_core(NULL) or
> > > > perf_pmus__find_by_type(evsel->core.attr.type or PERF_TYPE_RAW).
> > > > evsel->pmu->is_core && x86__is_amd_cpu() would identify an AMD core
> > > > PMU whereas the code above could fire for IBS or other PMUs.
> > >
> > > But IBS is the only PMU on AMD that provides precise_ip IIRC.  So I
> > > don't think other events would have it nor have any effect on changing
> > > the value.  So maybe we can skip the PMU scanning and just drop to 0?
> > 
> > cpu supports precise_ip as it forwards it to IBS, IBS is an ambiguous
> > term as there are ibs_op and ibs_fetch PMUs. The code is using values
> > in the attribute to infer the PMU that is being used, it feels it
> > would be more intention revealing to do things like:
> > ```
> > if (error == ... && perf_pmu__is_ibs_op_or_fetch(evsel->pmu)) ..
> > ```
> 
> I guess it'd get a core PMU for the default cycles event.  I think the
> intention is already confusing with the implicit forwarding.

What about this?

---8<---

From 70d39fb5c2956ba264a292f112f7fd7272dc91be Mon Sep 17 00:00:00 2001
From: Namhyung Kim <namhyung@kernel.org>
Date: Tue, 3 Sep 2024 22:50:09 -0700
Subject: [PATCH] perf tools: Check fallback error and order

The perf_event_open might fail due to various reasons, so blindly
reducing precise_ip level might not be the best way to deal with it.

It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
given precise level.  Let's try again with the correct error code.

This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
user events with exclude_kernel=1 cannot make progress.  Let's add the
evsel__handle_error_quirks() to this case specially.  I plan to work on
the kernel side to improve this situation but it'd still need some
special handling for IBS.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/util/evsel.c | 50 ++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 476658143822c346..2c45c55222c43dd4 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2246,6 +2246,43 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
 	return false;
 }
 
+/*
+ * AMD core PMU forwards some events with precise_ip to IBS implicitly.
+ * This logic matches to the kernel function (core_pmu_ibs_config).
+ */
+static bool evsel__is_implicit_ibs_event(struct evsel *evsel)
+{
+	if (evsel->core.attr.precise_ip == 0 || !x86__is_amd_cpu())
+		return false;
+
+	if (evsel->core.attr.type == PERF_TYPE_HARDWARE &&
+	    evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES)
+		return true;
+
+	if (evsel->core.attr.type == PERF_TYPE_RAW &&
+	    (evsel->core.attr.config == 0x76 || evsel->core.attr.config == 0xc1))
+		return true;
+
+	return false;
+}
+
+static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
+{
+	/*
+	 * AMD IBS doesn't support exclude_kernel, forward it back to the core
+	 * PMU by clearing precise_ip only if it's from precise_max (:P).
+	 */
+	if (error == -EINVAL && evsel__is_implicit_ibs_event(evsel) &&
+	    evsel->core.attr.exclude_kernel && evsel->precise_max) {
+		evsel->core.attr.precise_ip = 0;
+		pr_debug2_peo("removing precise_ip on AMD\n");
+		display_attr(&evsel->core.attr);
+		return true;
+	}
+
+	return false;
+}
+
 static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 		struct perf_thread_map *threads,
 		int start_cpu_map_idx, int end_cpu_map_idx)
@@ -2366,9 +2403,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	return 0;
 
 try_fallback:
-	if (evsel__precise_ip_fallback(evsel))
-		goto retry_open;
-
 	if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
 					 idx, threads, thread, err)) {
 		/* We just removed 1 thread, so lower the upper nthreads limit. */
@@ -2385,11 +2419,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
 		goto retry_open;
 
-	if (err != -EINVAL || idx > 0 || thread > 0)
-		goto out_close;
+	if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
+		goto retry_open;
 
-	if (evsel__detect_missing_features(evsel))
+	if (err == -EINVAL && evsel__detect_missing_features(evsel))
 		goto fallback_missing_features;
+
+	if (evsel__handle_error_quirks(evsel, err))
+		goto retry_open;
+
 out_close:
 	if (err)
 		threads->err_thread = thread;
-- 
2.47.0.rc1.288.g06298d1525-goog

On Mon, Oct 14, 2024 at 12:22 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hi Ian,
>
> On Thu, Oct 03, 2024 at 03:38:01PM -0700, Namhyung Kim wrote:
> > On Thu, Oct 03, 2024 at 10:32:47AM -0700, Ian Rogers wrote:
> > > On Thu, Oct 3, 2024 at 10:06 AM Namhyung Kim <namhyung@kernel.org> wrote:
> > > >
> > > > On Tue, Oct 01, 2024 at 03:21:50PM -0700, Ian Rogers wrote:
> > > > > On Tue, Oct 1, 2024 at 2:36 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > > > >
> > > > > > On Tue, Oct 01, 2024 at 11:00:20AM -0700, Ian Rogers wrote:
> > > > > > > On Mon, Sep 30, 2024 at 5:20 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > > > > > > >
> > > > > > > > The perf_event_open might fail due to various reasons, so blindly
> > > > > > > > reducing precise_ip level might not be the best way to deal with it.
> > > > > > > >
> > > > > > > > It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> > > > > > > > given precise level.  Let's try again with the correct error code.
> > > > > > > >
> > > > > > > > This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> > > > > > > > user events with exclude_kernel=1 cannot make progress.  Let's add the
> > > > > > > > evsel__handle_error_quirks() to this case specially.  I plan to work on
> > > > > > > > the kernel side to improve this situation but it'd still need some
> > > > > > > > special handling for IBS.
> > > > > > > >
> > > > > > > > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > > > > > > > ---
> > > > > > > >  tools/perf/util/evsel.c | 27 +++++++++++++++++++++------
> > > > > > > >  1 file changed, 21 insertions(+), 6 deletions(-)
> > > > > > > >
> > > > > > > > diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> > > > > > > > index 32e30c293d0c6198..ef8356260eea54cd 100644
> > > > > > > > --- a/tools/perf/util/evsel.c
> > > > > > > > +++ b/tools/perf/util/evsel.c
> > > > > > > > @@ -2419,6 +2419,20 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
> > > > > > > >         return false;
> > > > > > > >  }
> > > > > > > >
> > > > > > > > +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> > > > > > > > +{
> > > > > > > > +       /* AMD IBS doesn't support exclude_kernel, forward it to core PMU */
> > > > > > >
> > > > > > > Should the quirk handling be specific to evsels with the IBS PMU given
> > > > > > > the comment above? ie this is a PMU specific workaround rather than an
> > > > > > > AMD specific workaround, however, the PMU only exists on AMD :-)
> > > > > > >
> > > > > > > > +       if (error == -EINVAL && evsel->precise_max && evsel->core.attr.precise_ip &&
> > > > > > > > +           evsel->core.attr.exclude_kernel && x86__is_amd_cpu()) {
> > > > > > >
> > > > > > > So here rather than x86__is_amd_cpu it would be
> > > > > > > !strcmp(evsel->pmu->name, "ibs_...") . But it may be cleaner to move
> > > > > > > the logic into pmu.c.
> > > > > >
> > > > > > I guess the problem is that AMD driver does implicit forwarding to IBS
> > > > > > if the legacy hardware events have precise_ip.  So it might have just
> > > > > > core pmu (or no pmu) in the evsel.
> > > > >
> > > > > I think the no PMU case should probably have a PMU possibly similar to
> > > > > the tool PMU in:
> > > > > https://lore.kernel.org/all/20240912190341.919229-1-irogers@google.com/
> > > > > But that's not in place yet. You can always use
> > > > > perf_pmus__scan_core(NULL) or
> > > > > perf_pmus__find_by_type(evsel->core.attr.type or PERF_TYPE_RAW).
> > > > > evsel->pmu->is_core && x86__is_amd_cpu() would identify an AMD core
> > > > > PMU whereas the code above could fire for IBS or other PMUs.
> > > >
> > > > But IBS is the only PMU on AMD that provides precise_ip IIRC.  So I
> > > > don't think other events would have it nor have any effect on changing
> > > > the value.  So maybe we can skip the PMU scanning and just drop to 0?
> > >
> > > cpu supports precise_ip as it forwards it to IBS, IBS is an ambiguous
> > > term as there are ibs_op and ibs_fetch PMUs. The code is using values
> > > in the attribute to infer the PMU that is being used, it feels it
> > > would be more intention revealing to do things like:
> > > ```
> > > if (error == ... && perf_pmu__is_ibs_op_or_fetch(evsel->pmu)) ..
> > > ```
> >
> > I guess it'd get a core PMU for the default cycles event.  I think the
> > intention is already confusing with the implicit forwarding.
>
> What about this?
>
> ---8<---
>
> From 70d39fb5c2956ba264a292f112f7fd7272dc91be Mon Sep 17 00:00:00 2001
> From: Namhyung Kim <namhyung@kernel.org>
> Date: Tue, 3 Sep 2024 22:50:09 -0700
> Subject: [PATCH] perf tools: Check fallback error and order
>
> The perf_event_open might fail due to various reasons, so blindly
> reducing precise_ip level might not be the best way to deal with it.
>
> It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
> given precise level.  Let's try again with the correct error code.
>
> This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
> user events with exclude_kernel=1 cannot make progress.  Let's add the
> evsel__handle_error_quirks() to this case specially.  I plan to work on
> the kernel side to improve this situation but it'd still need some
> special handling for IBS.
>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/perf/util/evsel.c | 50 ++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 44 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 476658143822c346..2c45c55222c43dd4 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2246,6 +2246,43 @@ static bool evsel__detect_missing_features(struct evsel *evsel)
>         return false;
>  }
>
> +/*
> + * AMD core PMU forwards some events with precise_ip to IBS implicitly.
> + * This logic matches to the kernel function (core_pmu_ibs_config).
> + */
> +static bool evsel__is_implicit_ibs_event(struct evsel *evsel)
> +{
> +       if (evsel->core.attr.precise_ip == 0 || !x86__is_amd_cpu())
> +               return false;
> +
> +       if (evsel->core.attr.type == PERF_TYPE_HARDWARE &&
> +           evsel->core.attr.config == PERF_COUNT_HW_CPU_CYCLES)
> +               return true;

Lgtm, still seems strange we're not asserting something like
evsel->is_pmu_core. There's some clean up of that in (unmerged):
https://lore.kernel.org/lkml/20240918220133.102964-3-irogers@google.com/#t

Thanks,
Ian

> +
> +       if (evsel->core.attr.type == PERF_TYPE_RAW &&
> +           (evsel->core.attr.config == 0x76 || evsel->core.attr.config == 0xc1))
> +               return true;
> +
> +       return false;
> +}
> +
> +static bool evsel__handle_error_quirks(struct evsel *evsel, int error)
> +{
> +       /*
> +        * AMD IBS doesn't support exclude_kernel, forward it back to the core
> +        * PMU by clearing precise_ip only if it's from precise_max (:P).
> +        */
> +       if (error == -EINVAL && evsel__is_implicit_ibs_event(evsel) &&
> +           evsel->core.attr.exclude_kernel && evsel->precise_max) {
> +               evsel->core.attr.precise_ip = 0;
> +               pr_debug2_peo("removing precise_ip on AMD\n");
> +               display_attr(&evsel->core.attr);
> +               return true;
> +       }
> +
> +       return false;
> +}
> +
>  static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>                 struct perf_thread_map *threads,
>                 int start_cpu_map_idx, int end_cpu_map_idx)
> @@ -2366,9 +2403,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>         return 0;
>
>  try_fallback:
> -       if (evsel__precise_ip_fallback(evsel))
> -               goto retry_open;
> -
>         if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
>                                          idx, threads, thread, err)) {
>                 /* We just removed 1 thread, so lower the upper nthreads limit. */
> @@ -2385,11 +2419,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>         if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
>                 goto retry_open;
>
> -       if (err != -EINVAL || idx > 0 || thread > 0)
> -               goto out_close;
> +       if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> +               goto retry_open;
>
> -       if (evsel__detect_missing_features(evsel))
> +       if (err == -EINVAL && evsel__detect_missing_features(evsel))
>                 goto fallback_missing_features;
> +
> +       if (evsel__handle_error_quirks(evsel, err))
> +               goto retry_open;
> +
>  out_close:
>         if (err)
>                 threads->err_thread = thread;
> --
> 2.47.0.rc1.288.g06298d1525-goog
>

> @@ -2366,9 +2403,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>  	return 0;
>  
>  try_fallback:
> -	if (evsel__precise_ip_fallback(evsel))
> -		goto retry_open;
> -
>  	if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
>  					 idx, threads, thread, err)) {
>  		/* We just removed 1 thread, so lower the upper nthreads limit. */
> @@ -2385,11 +2419,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
>  	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
>  		goto retry_open;
>  
> -	if (err != -EINVAL || idx > 0 || thread > 0)
> -		goto out_close;
> +	if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> +		goto retry_open;

This will change the behavior of events like instructions:P on AMD.

Without patch:
  $ ./perf record -e instructions:P -- true
  [ perf record: Woken up 2 times to write data ]
  [ perf record: Captured and wrote 0.009 MB perf.data (9 samples) ]

With the patch:

  $ ./perf record -e instructions:P -- true
  Error:
  The instructions:Pu event is not supported.

Thanks,
Ravi

Hello Ravi,

On Tue, Oct 15, 2024 at 09:51:50AM +0530, Ravi Bangoria wrote:
> > @@ -2366,9 +2403,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> >  	return 0;
> >  
> >  try_fallback:
> > -	if (evsel__precise_ip_fallback(evsel))
> > -		goto retry_open;
> > -
> >  	if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),
> >  					 idx, threads, thread, err)) {
> >  		/* We just removed 1 thread, so lower the upper nthreads limit. */
> > @@ -2385,11 +2419,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
> >  	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))
> >  		goto retry_open;
> >  
> > -	if (err != -EINVAL || idx > 0 || thread > 0)
> > -		goto out_close;
> > +	if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))
> > +		goto retry_open;
> 
> This will change the behavior of events like instructions:P on AMD.
> 
> Without patch:
>   $ ./perf record -e instructions:P -- true
>   [ perf record: Woken up 2 times to write data ]
>   [ perf record: Captured and wrote 0.009 MB perf.data (9 samples) ]
> 
> With the patch:
> 
>   $ ./perf record -e instructions:P -- true
>   Error:
>   The instructions:Pu event is not supported.

Thanks for the test, it should support other events too.  I've noticed
it returns -ENOENT for non-IBS events with precise_ip > 0.  Will handle
them as well.

Thanks,
Namhyung