linux-kernel - Re: [PATCH 4/7] governors/haltpoll: Drop kvm_para

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Date:   Thu, 10 Aug 2023 21:25:41 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Mihai Carabas <mihai.carabas@...cle.com>
Cc:     Joao Martins <joao.m.martins@...cle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Juerg Haefliger <juerg.haefliger@...onical.com>,
        Mickaël Salaün <mic@...ikod.net>,
        Arnd Bergmann <arnd@...db.de>,
        Ankur Arora <ankur.a.arora@...cle.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvm@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 4/7] governors/haltpoll: Drop kvm_para_available() check

On Wed, Aug 9, 2023 at 2:54 PM Mihai Carabas <mihai.carabas@...cle.com> wrote:
>
> From: Joao Martins <joao.m.martins@...cle.com>
>
> This is duplicated already in the haltpoll idle driver,
> and there's no need to re-check KVM guest availability in
> the governor.
>
> Either guests uses the module which explicitly selects this
> governor, and given that it has the lowest rating of all governors
> (menu=20,teo=19,ladder=10/25,haltpoll=9) means that unless it's
> the only one compiled in, it won't be selected.
>
> Dropping such check also allows to test haltpoll in baremetal.

Fair enough.

> Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
> Signed-off-by: Mihai Carabas <mihai.carabas@...cle.com>

Acked-by: Rafael J. Wysocki <rafael@...nel.org>

> ---
>  drivers/cpuidle/governors/haltpoll.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
> index 1dff3a52917d..c9b69651d377 100644
> --- a/drivers/cpuidle/governors/haltpoll.c
> +++ b/drivers/cpuidle/governors/haltpoll.c
> @@ -143,10 +143,7 @@ static int haltpoll_enable_device(struct cpuidle_driver *drv,
>
>  static int __init init_haltpoll(void)
>  {
> -       if (kvm_para_available())
> -               return cpuidle_register_governor(&haltpoll_governor);
> -
> -       return 0;
> +       return cpuidle_register_governor(&haltpoll_governor);
>  }
>
>  postcore_initcall(init_haltpoll);
> --
> 1.8.3.1
>