linux-kernel - Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors based on the Zen microarchitecture

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Date:   Wed, 21 Sep 2022 16:09:16 +0530
From:   K Prateek Nayak <kprateek.nayak@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, rafael@...nel.org, lenb@...nel.org,
        linux-acpi@...r.kernel.org, linux-pm@...r.kernel.org,
        dave.hansen@...ux.intel.com, tglx@...utronix.de, andi@...as.de,
        puwen@...on.cn, mario.limonciello@....com, peterz@...radead.org,
        rui.zhang@...el.com, gpiccoli@...lia.com,
        daniel.lezcano@...aro.org, ananth.narayan@....com,
        gautham.shenoy@....com, Calvin Ong <calvin.ong@....com>,
        stable@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors
 based on the Zen microarchitecture

Hello Boris,

On 9/21/2022 2:17 PM, Borislav Petkov wrote:
> On Wed, Sep 21, 2022 at 12:06:38PM +0530, K Prateek Nayak wrote:
>> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
>> index 16a1663d02d4..18850aa2b79b 100644
>> --- a/drivers/acpi/processor_idle.c
>> +++ b/drivers/acpi/processor_idle.c
>> @@ -528,8 +528,11 @@ static int acpi_idle_bm_check(void)
>>  static void wait_for_freeze(void)
>>  {
>>  #ifdef	CONFIG_X86
>> -	/* No delay is needed if we are in guest */
>> -	if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
>> +	/*
>> +	 * No delay is needed if we are in guest or on a processor
>> +	 * based on the Zen microarchitecture.
>> +	 */
>> +	if (boot_cpu_has(X86_FEATURE_HYPERVISOR) || boot_cpu_has(X86_FEATURE_ZEN))
> 
> s/boot_cpu_has/cpu_feature_enabled/g

I was not aware of cpu_feature_enabled() and it makes perfect sense to
use it here. Thank you for bringing it to my notice.
I'll make this change in v2.

> 
> while at it.
> 

--
Thanks and Regards,
Prateek