linux-kernel - Re: [RFC PATCH v4 8/8] acpi_idle: Disallow play

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Message-ID: <CAJZ5v0jnbf-BpikaVayfW=5Rrf61XNtW1JyraJ_V=advADe_VQ@mail.gmail.com>
Date: Mon, 25 Nov 2024 14:46:46 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, 
	rafael.j.wysocki@...el.com, len.brown@...el.com, 
	artem.bityutskiy@...ux.intel.com, dave.hansen@...ux.intel.com, 
	peterz@...radead.org, tglx@...utronix.de, gautham.shenoy@....com
Subject: Re: [RFC PATCH v4 8/8] acpi_idle: Disallow play_dead with FFH cstate
 on AMD platforms

On Mon, Nov 25, 2024 at 2:21 PM Patryk Wlazlyn
<patryk.wlazlyn@...ux.intel.com> wrote:
>
> Signed-off-by: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
> Suggested-by: Gautham R. Shenoy <gautham.shenoy@....com>
> ---
>  drivers/acpi/processor_idle.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 586cc7d1d8aa..4b4ac8d55b55 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -803,7 +803,11 @@ static int acpi_processor_setup_cstates(struct acpi_processor *pr)
>
>                 state->flags = 0;
>
> -               state->enter_dead = acpi_idle_play_dead;
> +               /* AMD doesn't want to use mwait for play dead. */
> +               bool amd_or_hygon = boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
> +                                   boot_cpu_data.x86_vendor == X86_VENDOR_HYGON;
> +               if (!(cx->entry_method == ACPI_CSTATE_FFH && amd_or_hygon))
> +                       state->enter_dead = acpi_idle_play_dead;
>
>                 if (cx->type == ACPI_STATE_C1 || cx->type == ACPI_STATE_C2)
>                         drv->safe_state_index = count;
> --

I don't think this is needed.

There is a vendor check in mwait_play_dead() already, no need to
duplicate it in the otherwise arch-agnostic ACPI code.