linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Disable SMT when hybrid systems are enabled

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Message-ID: <7cc76b59-964d-4ce2-b3c4-e1337dbe0c67@kylinos.cn>
Date: Fri, 23 Jan 2026 09:20:09 +0800
From: Yaxiong Tian <tianyaxiong@...inos.cn>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc: srinivas.pandruvada@...ux.intel.com, lenb@...nel.org, rafael@...nel.org,
 viresh.kumar@...aro.org, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: intel_pstate: Disable SMT when hybrid systems
 are enabled


在 2026/1/22 23:55, Ricardo Neri 写道:
> On Mon, Jan 19, 2026 at 03:41:18PM +0800, Yaxiong Tian wrote:
>> When hwp_is_hybrid && !sched_smt_active(), the driver enables
>> hybrid_capacity_scale and disables ITMT. According to the original code
>> logic, these related actions are one-time operations; therefore, I
>> believe the original design intent did not support dynamic runtime
>> switching.
>>
>> However, SMT can be toggled via related interfaces in /sys. When SMT is
>> enabled, the system is no longer hybrid, and the original settings become
>> incorrect.
> Indeed I was able to enable SMT siblings:
>
> 	$ echo on > /sys/devices/system/cpu/smt
> 	$ echo 1 > /sys/devices/system/cpu/cpu1/online
>
>> To resolve this confusion, permanently disable SMT by calling
>> cpuhp_smt_disable().
> IMHO, the user should be able to enable SMT back if she or he chooses to. Instead,
> the sched domains should be rebuilt with asym packing and without asymmetric
> capacity.
Yes, I also agree with this viewpoint. I think a better solution is to 
place it within cpufreq online for heterogeneous judgment and to clearly 
address sched domain rebuilt and asymmetry issues. I ran some tests the 
day before yesterday and encountered a few locking problems. I will 
publish the patch a bit later.