linux-kernel - [PATCH 0/4] ACPI: CPPC: Fixes to limit actions to online CPUs

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Message-ID: <20251105143851.4251-1-gautham.shenoy@amd.com>
Date: Wed, 5 Nov 2025 20:08:47 +0530
From: "Gautham R. Shenoy" <gautham.shenoy@....com>
To: "Rafael J . Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
	Mario Limonciello <mario.limonciello@....com>, Yunhui Cui
	<cuiyunhui@...edance.com>, Jeremy Linton <jeremy.linton@....com>, "Viresh
 Kumar" <viresh.kumar@...aro.org>, Ionela Voinescu <ionela.voinescu@....com>
CC: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>, "Christopher
 Harris" <chris.harris79@...il.com>, <linux-pm@...r.kernel.org>, "Gautham R.
 Shenoy" <gautham.shenoy@....com>
Subject: [PATCH 0/4] ACPI: CPPC: Fixes to limit actions to online CPUs

Hello,

Christopher Harris reported a regression between v6.10 to v6.11 that
the amd-pstate driver failed to load even when the commandline had
"amd_pstate=passive"
(https://lore.kernel.org/lkml/CAM+eXpdDT7KjLV0AxEwOLkSJ2QtrsvGvjA2cCHvt1d0k2_C4Cw@mail.gmail.com/)

On debugging the issue it was observed that when the commandline
contains "nosmt=force", the CPPC code fails when performing certain
checks such as checking for the presence of preferred cores and
validity of the _CPC object since it iterates through all "present"
CPUs while the object state was populated only for "online" CPUs.

This patchset contains fixes to address this issue.

The first two patches in the series address the issue reported by
Chris.

Patches 3 and 4 harden the code in a couple of more functions which
iterated through the present CPUs when it is more apt to restrict the
operations to online CPUs

Gautham R. Shenoy (4):
  ACPI: CPPC: Detect preferred core availability on online CPUs
  ACPI: CPPC: Check _CPC validity for only the online CPUs
  ACPI: CPPC: Perform fast check switch only for online CPUs
  ACPI: CPPC: Limit perf ctrs in PCC check only to online CPUs

 arch/x86/kernel/acpi/cppc.c | 2 +-
 drivers/acpi/cppc_acpi.c    | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

-- 
2.34.1