linux-kernel - Re: [PATCH v1 3/4] ACPI: OSL: Allow Notify () handlers to run on all CPUs

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Message-ID: <ZWdF_XdUD6gxtYIW@smile.fi.intel.com>
Date:   Wed, 29 Nov 2023 16:09:01 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Michal Wilczynski <michal.wilczynski@...el.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v1 3/4] ACPI: OSL: Allow Notify () handlers to run on all
 CPUs

On Wed, Nov 29, 2023 at 02:50:54PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Notify () handlers, like GPE handlers, are only allowed to run on CPU0
> now out of the concern that they might trigger an SMM trap and that (in
> some cases) the SMM code running as a result of that might corrupt
> memory if not run on CPU0.

Pardon my French, but I'm a bit lost in the semantics of all those "that".
Maybe the above can be simplified?

> However, Notify () handlers are registered by kernel code and they
> are not likely to evaluate AML that would trigger an SMM trap.  In
> fact, many of them don't even evaluate any AML at all and even if
> they do, that AML may as well be evaluated in other code paths.  In
> other words, they are not special from the AML evaluation perspective,
> so there is no real reason to treat them in any special way.
> 
> Accordingly, allow Notify () handlers, unlike GPE handlers, to be
> executed by all CPUs in the system.
> 
> Also adjust the allocation of the "notify" workqueue to allow multiple
> handlers to be executed at the same time, because they need not be
> serialized.

Code wise LGTM,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko