From: Mark Rutland mark.rutland@arm.com
[ Upstream commit 25412c0364f7110faa6053c73e3fd47ca956b8c3 ]
Currently the perf tool doesn't detect support for extended event types on Apple M1/M2 systems, and will not auto-expand plain PERF_EVENT_TYPE hardware events into per-PMU events. This is due to the detection of extended event types not handling mandatory filters required by the M1/M2 PMU driver.
PMU drivers and the core perf_events code can require that perf_event_attr::exclude_* filters are configured in a specific way and may reject certain configurations of filters, for example:
(a) Many PMUs lack support for any event filtering, and require all perf_event_attr::exclude_* bits to be clear. This includes Alpha's CPU PMU, and ARM CPU PMUs prior to the introduction of PMUv2 in ARMv7,
(b) When /proc/sys/kernel/perf_event_paranoid >= 2, the perf core requires that perf_event_attr::exclude_kernel is set.
(c) The Apple M1/M2 PMU requires that perf_event_attr::exclude_guest is set as the hardware PMU does not count while a guest is running (but might be extended in future to do so).
In is_event_supported(), we try to account for cases (a) and (b), first attempting to open an event without any filters, and if this fails, retrying with perf_event_attr::exclude_kernel set. We do not account for case (c), or any other filters that drivers could theoretically require to be set.
Thus is_event_supported() will fail to detect support for any events targeting an Apple M1/M2 PMU, even where events would be supported with perf_event_attr:::exclude_guest set.
Since commit:
82fe2e45cdb00de4 ("perf pmus: Check if we can encode the PMU number in perf_event_attr.type")
... we use is_event_supported() to detect support for extended types, with the PMU ID encoded into the perf_event_attr::type. As above, on an Apple M1/M2 system this will always fail to detect that the event is supported, and consequently we fail to detect support for extended types even when these are supported, as they have been since commit:
5c816728651ae425 ("arm_pmu: Add PERF_PMU_CAP_EXTENDED_HW_TYPE capability")
Due to this, the perf tool will not automatically expand plain PERF_TYPE_HARDWARE events into per-PMU events, even when all the necessary kernel support is present.
This patch updates is_event_supported() to additionally try opening events with perf_event_attr::exclude_guest set, allowing support for events to be detected on Apple M1/M2 systems. I believe that this is sufficient for all contemporary CPU PMU drivers, though in future it may be necessary to check for other combinations of filter bits.
I've deliberately changed the check to not expect a specific error code for missing filters, as today ;the kernel may return a number of different error codes for missing filters (e.g. -EACCESS, -EINVAL, or -EOPNOTSUPP) depending on why and where the filter configuration is rejected, and retrying for any error is more robust.
Note that this does not remove the need for commit:
a24d9d9dc096fc0d ("perf parse-events: Make legacy events lower priority than sysfs/JSON")
... which is still necessary so that named-pmu/event/ events work on kernels without extended type support, even if the event name happens to be the same as a PERF_EVENT_TYPE_HARDWARE event (e.g. as is the case for the M1/M2 PMU's 'cycles' and 'instructions' events).
Fixes: 82fe2e45cdb00de4 ("perf pmus: Check if we can encode the PMU number in perf_event_attr.type") Signed-off-by: Mark Rutland mark.rutland@arm.com Tested-by: Ian Rogers irogers@google.com Tested-by: James Clark james.clark@arm.com Tested-by: Marc Zyngier maz@kernel.org Cc: Hector Martin marcan@marcan.st Cc: James Clark james.clark@arm.com Cc: John Garry john.g.garry@oracle.com Cc: Leo Yan leo.yan@linux.dev Cc: Mike Leach mike.leach@linaro.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Cc: Thomas Richter tmricht@linux.ibm.com Cc: Will Deacon will@kernel.org Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Namhyung Kim namhyung@kernel.org Link: https://lore.kernel.org/r/20240126145605.1005472-1-mark.rutland@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/perf/util/print-events.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c index a7566edc86a3e..9bee082194d5e 100644 --- a/tools/perf/util/print-events.c +++ b/tools/perf/util/print-events.c @@ -232,7 +232,6 @@ void print_sdt_events(const struct print_callbacks *print_cb, void *print_state) bool is_event_supported(u8 type, u64 config) { bool ret = true; - int open_return; struct evsel *evsel; struct perf_event_attr attr = { .type = type, @@ -246,20 +245,32 @@ bool is_event_supported(u8 type, u64 config)
evsel = evsel__new(&attr); if (evsel) { - open_return = evsel__open(evsel, NULL, tmap); - ret = open_return >= 0; + ret = evsel__open(evsel, NULL, tmap) >= 0;
- if (open_return == -EACCES) { + if (!ret) { /* - * This happens if the paranoid value + * The event may fail to open if the paranoid value * /proc/sys/kernel/perf_event_paranoid is set to 2 - * Re-run with exclude_kernel set; we don't do that - * by default as some ARM machines do not support it. - * + * Re-run with exclude_kernel set; we don't do that by + * default as some ARM machines do not support it. */ evsel->core.attr.exclude_kernel = 1; ret = evsel__open(evsel, NULL, tmap) >= 0; } + + if (!ret) { + /* + * The event may fail to open if the PMU requires + * exclude_guest to be set (e.g. as the Apple M1 PMU + * requires). + * Re-run with exclude_guest set; we don't do that by + * default as it's equally legitimate for another PMU + * driver to require that exclude_guest is clear. + */ + evsel->core.attr.exclude_guest = 1; + ret = evsel__open(evsel, NULL, tmap) >= 0; + } + evsel__delete(evsel); }