Re: [PATCH 2/9] x86/mwait-idle: clean up BYT/CHT auto demotion disable

[Jan Beulich <jbeulich@suse.com>]

On 24.04.2026 16:47, Roger Pau Monné wrote:
> On Thu, Mar 12, 2026 at 05:54:56PM +0100, Jan Beulich wrote:
>> @@ -1700,12 +1694,24 @@ static void mwait_idle_cpu_tweak(unsigne
>>  	case C1E_PROMOTION_PRESERVE:
>>  		break;
>>  	}
>> +
>> +	/* Pkg-scope MSRs on 1-socket-only systems need writing only once. */
>> +	if (!bsp)
>> +		return;
>> +
>> +	switch (boot_cpu_data.vfm) {
>> +	case INTEL_ATOM_SILVERMONT:
>> +	case INTEL_ATOM_AIRMONT:
>> +		byt_cht_auto_demotion_disable();
>> +		break;
>> +	}
>>  }
>>  
>>  static int cf_check mwait_idle_cpu_init(
>>      struct notifier_block *nfb, unsigned long action, void *hcpu)
>>  {
>>  	unsigned int cpu = (unsigned long)hcpu, cstate;
>> +	static bool first;
> 
> I think you want to init first = true here, so that after the first
> call to mwait_idle_cpu_tweak() it gets set to false for future calls?

Ouch, yes, definitely.

Jan