linux-kernel - Re: [RFC PATCH v4 5/8] x86/smp native_play_dead: Prefer cpuidle_play_dead() over mwait_play

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Message-ID: <a8d53d86-d658-4e18-bfd6-b37a2656b180@linux.intel.com>
Date: Tue, 26 Nov 2024 12:56:01 +0100
From: Patryk Wlazlyn <patryk.wlazlyn@...ux.intel.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
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 5/8] x86/smp native_play_dead: Prefer
 cpuidle_play_dead() over mwait_play_dead()

>>> If you first make intel_idle provide :enter_dead() for all CPUs on all
>>> platforms and implement it by calling mwait_play_dead_with_hint(), you
>>> won't need mwait_play_dead() any more.
>> Crossed my mind, but because mwait_play_dead doesn't filter on Intel
>> vendor specifically,
>
> In practice, it does.
>
> The vendor check in it is equivalent to "if Intel".

Actually, what about INTEL_IDLE=n?
We might hit acpi_idle, which would call mwait_play_dead_with_hint() now, but
if we don't, don't we want to try mwait_play_dead before hlt or is it too
unrealistic to happen?