Re: [PATCH 0/2] ACPI/CPPC: make policy-limit updates safe

On Wed, Jul 22, 2026 at 11:38 AM Christian Loehle
<[email protected]> wrote:
>
> Commit ea3db45ae476 ("cpufreq: cppc: Update MIN_PERF/MAX_PERF in target
> callbacks") made cppc-cpufreq submit policy bounds from both target
> callbacks. Two correctness issues remain in that path.
>
> ACPI permits the CPPC controls to use different address spaces. Fast
> switching can consequently enter the sleeping PCC path when DESIRED_PERF
> is directly accessible but MIN_PERF or MAX_PERF is PCC-backed. Fix it by
> doing the simple thing and only allowing fast-switch when all controls
> are directly accessible.
>
> The policy bounds are also read without the policy lock. Because the core
> updates policy->min and policy->max separately, a lockless reader can form
> an inverted pair. Patch 2 sanitizes that snapshot before converting it to
> CPPC performance values.
>
> Christian Loehle (2):
>   ACPI: CPPC: Check all controls for fast switching
>   cpufreq: cppc: Sanitize lockless policy limit snapshots
>
>  drivers/acpi/cppc_acpi.c       | 22 +++++++++++++++++-----
>  drivers/cpufreq/cppc_cpufreq.c | 33 +++++++++++++++++++++++----------
>  include/acpi/cppc_acpi.h       |  5 +++--
>  3 files changed, 43 insertions(+), 17 deletions(-)
>
> --

Applied as 7.2-rc material, thanks!