On machines without a usable core PMU, like an aarch64 box with no DT
node for the ARM PMU, the expectations that pin the legacy hardware
encoding can't be checked: without a core PMU at all 'cycles' doesn't
even resolve, and with one that can't be opened 'perf record' takes the
software fallback and records attributes they can never match:
expected type=0, got 1
expected config=0, got 1
FAILED '.../attr/test-record-group-sampling1' - match failure
And since attr.py stops at the first failure, every expectation that
would come after that one ends up not being run at all.
Add a 'requires' limitation, modelled after the existing 'arch', 'auxv'
and 'kernel_since/until' ones, with 'core-pmu' as its first value, that
is checked by asking perf itself to open 'cycles' via its python
binding: a parse failure or an ENOENT means there is no PMU that can
count it, hence nothing to check and the test gets skipped, while any
other error means we can't tell, so the test keeps running as it does
today, where there is no binding to ask either.
When there is no core PMU, asking the binding fails and prints a parse
error, once for every test that asks, so the answer is kept: it is asked
once per run. A value other than 'core-pmu' is warned about, not
silently ignored, so a typo can't turn the skip into a no-op.
An old distro python package may have a 'perf' module without
parse_events(), i.e. there is nothing to ask with, so that
AttributeError gets the same treatment as the ImportError: let the
expectations speak.
The expectations that have a strict 'type=0', plus the group tests,
where the fallback drops a member and leaves nothing to compare the
group leader attributes with, now state that they require a core PMU.
They are marked here, before the commit that has the group tests ask for
the legacy encodings, so the requisite comes with that dependency.
Reviewed-by: Ian Rogers <irogers@google.com>
Tested-by: Ian Rogers <irogers@google.com>
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>