Re: [PATCH v1 0/2] Fix RAPL PMU access from non-lead CPUs

[Rafael J. Wysocki]

On Tue, Feb 10, 2026 at 6:53 PM srinivas pandruvada
<srinivas.pandruvada@xxxxxxxxxxxxxxx> wrote:
>
> On Mon, 2026-02-09 at 15:43 -0800, Kuppuswamy Sathyanarayanan wrote:
> > This series fixes issues with RAPL PMU event access when using CPUs
> > other than the package lead_cpu.
> >
> > The problem was discovered when turbostat reported zero power values
> > when run on a non-lead CPU in the package.
> >
> > Investigation revealed two issues:
> >
> > 1. The RAPL MSR driver incorrectly validated that the current CPU
> > must
> >    match the lead CPU of the package when reading from PMU context,
> > even
> >    though package-scoped MSRs are readable from any CPU in the
> > package.
> >
> > 2. The RAPL PMU cpumask only exposed one CPU per package (the
> > lead_cpu)
> >    for both MSR and TPMI interfaces, forcing tools to use that
> > specific
> >    CPU even though package-scoped registers are readable from any CPU
> >    in the package.
> >
> > The perf tool avoided issue #1 by checking the cpumask before opening
> > events, but turbostat does not perform this validation. The
> > restrictive
> > cpumask in issue #2 was unnecessary since both MSR and TPMI
> > interfaces
> > support reads from any CPU in the package for package-scoped
> > registers.
> >
> > These patches:
> > - Remove the incorrect CPU validation check in PMU context
> > - Expand the PMU cpumask to include all CPUs in each package for both
> >   MSR and TPMI RAPL interfaces
> > - Rename 'atomic' parameter to 'pmu_ctx' for clarity
> >
> > After these changes, tools can successfully read RAPL events from any
> > CPU in the package, matching the architectural capability of the
> > hardware for both MSR and TPMI based RAPL implementations.
> >
> > Testing (PTL & GNR platform):
> > - Verified turbostat --no-msr --show power works on all CPUs
> > - Verified perf stat -e power/energy-pkg/ works on all CPUs
> > - Confirmed /sys/bus/event_source/devices/power/cpumask shows all
> >   package CPUs instead of just lead_cpu
> > - Tested on both MSR-based (PTL) and TPMI-based (GNR) RAPL system
> >
> > Kuppuswamy Sathyanarayanan (2):
> >   powercap: intel_rapl: Remove incorrect CPU check in PMU context
> >   powercap: intel_rapl: Expose all package CPUs in PMU cpumask
> >
>
> Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>

Both patches applied as 7.0-rc material, thanks!