Re: [PATCH v2] perf evlist: Don't restrict uncore events to PMU CPUs

The PMU CPU map has different semantics for core and uncore PMUs.

For core PMUs, pmu_cpus contains the CPUs on which the event can be
opened. Intersect the user-requested CPU map with the PMU CPU map to
reject CPUs unsupported by the PMU.

For uncore PMUs, pmu_cpus is read from the PMU's cpumask sysfs attribute,
which lists the default CPU to open the event on per socket/die, not the
set of CPUs it can only be opened on. The user-requested CPU may override
these defaults, and the driver can redirect the event to the appropriate
control CPU.

Currently, __perf_evlist__propagate_maps() intersects the user-requested
CPU map with pmu_cpus for all PMUs. If the user-requested CPU is not in
pmu_cpus, the intersection becomes empty and the evsel is removed before
perf_event_open() is called.

Add evsel->is_pmu_uncore, set once from pmu->is_uncore at parse time,
to skip the intersection for uncore PMUs. Core PMUs, and other
non-core PMUs such as software events, breakpoints, or tracepoints,
continue to be restricted to their PMU CPU map.

Fixes: 811082e4b668 ("perf parse-events: Support user CPUs mixed with threads/processes")

Assisted-by: Claude Sonnet 5
Signed-off-by: Nia Su <redacted>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260909-perf-evlist-uncore-cpu-b4-v2-1-dc673a1f4592@sifive.com?part=1