[PATCH 6.19 064/781] cpufreq: intel_pstate: Enable asym capacity only when CPU SMT is not possible

Greg Kroah-Hartman
2026-02-25T01:29:01Z

From: Yaxiong Tian <tianyaxiong@kylinos.cn>

[ Upstream commit 1fedbb589448bee9f20bb2ed9c850d1d2cf9963c ]

According to the description in the intel_pstate.rst documentation,
Capacity-Aware Scheduling and Energy-Aware Scheduling are only
supported on a hybrid processor without SMT. Previously, the system
used sched_smt_active() for judgment, which is not a strict condition
because users can switch it on or off via /sys at any time.

This could lead to incorrect driver settings in certain scenarios.
For example, on a CPU that supports SMT, a user can disable SMT
via the nosmt parameter to enable asym capacity, and then re-enable
SMT via /sys. In such cases, some settings in the driver would no
longer be correct.

To address this issue, replace sched_smt_active() with cpu_smt_possible(),
and only enable asym capacity when CPU SMT is not possible.

Fixes: 929ebc93ccaa ("cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems")
Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20260203024852.301066-1-tianyaxiong@kylinos.cn
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/cpufreq/intel_pstate.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index ec4abe3745736..1625ec2d0d06a 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1161,7 +1161,7 @@ static void hybrid_init_cpu_capacity_scaling(bool refresh)
* the capacity of SMT threads is not deterministic even approximately,
* do not do that when SMT is in use.
*/
- if (hwp_is_hybrid && !sched_smt_active() && arch_enable_hybrid_capacity_scale()) {
+ if (hwp_is_hybrid && !cpu_smt_possible() && arch_enable_hybrid_capacity_scale()) {
hybrid_refresh_cpu_capacity_scaling();
/*
* Disabling ITMT causes sched domains to be rebuilt to disable asym
--
2.51.0