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Message-ID: <a7b7df27-d49c-a6a7-46a0-47cc1098e644@linux.ibm.com>
Date:   Wed, 5 Jul 2023 13:57:05 +0200
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Subject: Re: [PATCH v3 6/9] cpu/SMT: Allow enabling partial SMT states via
 sysfs
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To:     "Zhang, Rui" <rui.zhang@intel.com>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Cc:     lkp <lkp@intel.com>, "npiggin@gmail.com" <npiggin@gmail.com>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>,
        "christophe.leroy@csgroup.eu" <christophe.leroy@csgroup.eu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "mpe@ellerman.id.au" <mpe@ellerman.id.au>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
References: <20230629143149.79073-1-ldufour@linux.ibm.com>
 <20230629143149.79073-7-ldufour@linux.ibm.com>
 <5801fb9a94c2ce00ca44220be0b1a5bd7f8ff44f.camel@intel.com>
From:   Laurent Dufour <ldufour@linux.ibm.com>
In-Reply-To: <5801fb9a94c2ce00ca44220be0b1a5bd7f8ff44f.camel@intel.com>
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Le 05/07/2023 à 05:14, Zhang, Rui a écrit :
> On Thu, 2023-06-29 at 16:31 +0200, Laurent Dufour wrote:
>> @@ -2580,6 +2597,17 @@ static ssize_t control_show(struct device
>> *dev,
>>   {
>>          const char *state = smt_states[cpu_smt_control];
>>   
>> +#ifdef CONFIG_HOTPLUG_SMT
>> +       /*
>> +        * If SMT is enabled but not all threads are enabled then
>> show the
>> +        * number of threads. If all threads are enabled show "on".
>> Otherwise
>> +        * show the state name.
>> +        */
>> +       if (cpu_smt_control == CPU_SMT_ENABLED &&
>> +           cpu_smt_num_threads != cpu_smt_max_threads)
>> +               return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
>> +#endif
>> +
> 
> My understanding is that cpu_smt_control is always set to
> CPU_SMT_NOT_IMPLEMENTED when CONFIG_HOTPLUG_SMT is not set, so this
> ifdef is not necessary, right?

Hi Rui,

Indeed, cpu_smt_control, cpu_smt_num_threads and cpu_smt_max_threads are 
only defined when CONFIG_HOTPLUG_SMT is set. This is the reason for this 
#ifdef block.

This has been reported by the kernel test robot testing v2:
https://lore.kernel.org/oe-kbuild-all/202306282340.Ihqm0fLA-lkp@intel.com

Cheers,
Laurent.