linux-kernel - Re: [PATCH 2/7] x86/kvm: Move haltpoll

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Date:   Wed, 29 Nov 2023 21:55:42 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Mihai Carabas <mihai.carabas@...cle.com>
Cc:     linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        pbonzini@...hat.com, wanpengli@...cent.com, vkuznets@...hat.com,
        rafael@...nel.org, daniel.lezcano@...aro.org,
        akpm@...ux-foundation.org, pmladek@...e.com, peterz@...radead.org,
        dianders@...omium.org, npiggin@...il.com,
        rick.p.edgecombe@...el.com, joao.m.martins@...cle.com,
        juerg.haefliger@...onical.com, mic@...ikod.net, arnd@...db.de,
        ankur.a.arora@...cle.com
Subject: Re: [PATCH 2/7] x86/kvm: Move haltpoll_want() to be arch defined

On Mon, Nov 20, 2023 at 4:15 PM Mihai Carabas <mihai.carabas@...cle.com> wrote:
>
> From: Joao Martins <joao.m.martins@...cle.com>
>
> Right now, kvm_para_has_hint(KVM_HINTS_REALTIME) is x86 only, and so in the
> pursuit of making cpuidle-haltpoll arch independent, move the check for
> haltpoll enablement to be defined per architecture. Same thing for
> boot_option_idle_override. To that end, add a arch_haltpoll_want() and move the
> check there.
>
> Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
> Signed-off-by: Mihai Carabas <mihai.carabas@...cle.com>

>From the cpuidle side:

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

> ---
>  arch/x86/include/asm/cpuidle_haltpoll.h |  1 +
>  arch/x86/kernel/kvm.c                   | 10 ++++++++++
>  drivers/cpuidle/cpuidle-haltpoll.c      |  8 ++------
>  include/linux/cpuidle_haltpoll.h        |  5 +++++
>  4 files changed, 18 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/cpuidle_haltpoll.h b/arch/x86/include/asm/cpuidle_haltpoll.h
> index c8b39c6716ff..2c5a53ce266f 100644
> --- a/arch/x86/include/asm/cpuidle_haltpoll.h
> +++ b/arch/x86/include/asm/cpuidle_haltpoll.h
> @@ -4,5 +4,6 @@
>
>  void arch_haltpoll_enable(unsigned int cpu);
>  void arch_haltpoll_disable(unsigned int cpu);
> +bool arch_haltpoll_want(void);
>
>  #endif
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 1cceac5984da..75a24f107b2a 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -1151,4 +1151,14 @@ void arch_haltpoll_disable(unsigned int cpu)
>         smp_call_function_single(cpu, kvm_enable_host_haltpoll, NULL, 1);
>  }
>  EXPORT_SYMBOL_GPL(arch_haltpoll_disable);
> +
> +bool arch_haltpoll_want(void)
> +{
> +       /* Do not load haltpoll if idle= is passed */
> +       if (boot_option_idle_override != IDLE_NO_OVERRIDE)
> +               return false;
> +
> +       return kvm_para_has_hint(KVM_HINTS_REALTIME);
> +}
> +EXPORT_SYMBOL_GPL(arch_haltpoll_want);
>  #endif
> diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
> index e66df22f9695..72f9c84990c5 100644
> --- a/drivers/cpuidle/cpuidle-haltpoll.c
> +++ b/drivers/cpuidle/cpuidle-haltpoll.c
> @@ -96,7 +96,7 @@ static void haltpoll_uninit(void)
>
>  static bool haltpoll_want(void)
>  {
> -       return kvm_para_has_hint(KVM_HINTS_REALTIME) || force;
> +       return (kvm_para_available() && arch_haltpoll_want()) || force;
>  }
>
>  static int __init haltpoll_init(void)
> @@ -104,11 +104,7 @@ static int __init haltpoll_init(void)
>         int ret;
>         struct cpuidle_driver *drv = &haltpoll_driver;
>
> -       /* Do not load haltpoll if idle= is passed */
> -       if (boot_option_idle_override != IDLE_NO_OVERRIDE)
> -               return -ENODEV;
> -
> -       if (!kvm_para_available() || !haltpoll_want())
> +       if (!haltpoll_want())
>                 return -ENODEV;
>
>         cpuidle_poll_state_init(drv);
> diff --git a/include/linux/cpuidle_haltpoll.h b/include/linux/cpuidle_haltpoll.h
> index d50c1e0411a2..bae68a6603e3 100644
> --- a/include/linux/cpuidle_haltpoll.h
> +++ b/include/linux/cpuidle_haltpoll.h
> @@ -12,5 +12,10 @@ static inline void arch_haltpoll_enable(unsigned int cpu)
>  static inline void arch_haltpoll_disable(unsigned int cpu)
>  {
>  }
> +
> +static inline bool arch_haltpoll_want(void)
> +{
> +       return false;
> +}
>  #endif
>  #endif
> --
> 1.8.3.1
>