[PATCH RESEND] cpufreq: intel_pstate: Sync policy->cur when setting min pstate during CPU offline

[PATCH RESEND] cpufreq: intel_pstate: Sync policy->cur when setting min pstate during CPU offline

[Fushuai Wang]

From: Fushuai Wang <wangfushuai@baidu.com>

When a CPU goes offline with HWP disabled, intel_pstate_set_min_pstate()
sets the MSR_IA32_PERF_CTL to minimum frequency to prevent SMT siblings
from being restricted. However, the policy->cur value was not updated,
leaving it at the previous value.

When the CPU comes back online, governor->limits() checks if target_freq
equals policy->cur and skips the frequency adjustment if they match. Since
policy->cur still holds the previous value, the governor does not call
cpufreq_driver->target to update MSR_IA32_PERF_CTL.

Fix this by synchronizing policy->cur with the hardware state when setting
minimum pstate during CPU offline.

Fixes: f6ebbcf08f37 ("cpufreq: intel_pstate: Implement passive mode with HWP enabled")
Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
---
 drivers/cpufreq/intel_pstate.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 1292da53e5fc..0bd6388caa9d 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2986,8 +2986,10 @@ static int intel_cpufreq_cpu_offline(struct cpufreq_policy *policy)
 	 */
 	if (hwp_active)
 		intel_pstate_hwp_offline(cpu);
-	else
+	else {
 		intel_pstate_set_min_pstate(cpu);
+		policy->cur = cpu->pstate.min_freq;
+	}
 
 	intel_pstate_exit_perf_limits(policy);
 
-- 
2.36.1

Re: [PATCH RESEND] cpufreq: intel_pstate: Sync policy->cur when setting min pstate during CPU offline

[srinivas pandruvada]

On Tue, 2026-05-19 at 19:24 +0800, Fushuai Wang wrote:
> From: Fushuai Wang <wangfushuai@baidu.com>
> 
> When a CPU goes offline with HWP disabled,
> intel_pstate_set_min_pstate()
> sets the MSR_IA32_PERF_CTL to minimum frequency to prevent SMT
> siblings
> from being restricted. However, the policy->cur value was not
> updated,
> leaving it at the previous value.
> 
> When the CPU comes back online, governor->limits() checks if
> target_freq
> equals policy->cur and skips the frequency adjustment if they match.
> Since
> policy->cur still holds the previous value, the governor does not
> call
> cpufreq_driver->target to update MSR_IA32_PERF_CTL.
> 
> Fix this by synchronizing policy->cur with the hardware state when
> setting
> minimum pstate during CPU offline.
> 
> Fixes: f6ebbcf08f37 ("cpufreq: intel_pstate: Implement passive mode
> with HWP enabled")

The patch is fine with some comments below, but this Fixes tag is not
necessary added this. This was implementation from
Commit bb18008f8086283f8f03e8e50fbbf17f213b9ea9
Author: Dirk Brandewie <dirk.j.brandewie@intel.com>
Date:   Wed Mar 19 08:45:54 2014 -0700

    intel_pstate: Set core to min P state during core offline
 


> Signed-off-by: Fushuai Wang <wangfushuai@baidu.com>
> ---
>  drivers/cpufreq/intel_pstate.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c
> b/drivers/cpufreq/intel_pstate.c
> index 1292da53e5fc..0bd6388caa9d 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -2986,8 +2986,10 @@ static int intel_cpufreq_cpu_offline(struct
> cpufreq_policy *policy)
>  	 */
>  	if (hwp_active)

{

>  		intel_pstate_hwp_offline(cpu);
> -	else
> +	else {

s/else / } else {

>  		intel_pstate_set_min_pstate(cpu);
> +		policy->cur = cpu->pstate.min_freq;
> +	}

>  
>  	intel_pstate_exit_perf_limits(policy);
>