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From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: Thu, 22 Sep 2022 17:53:17 +0200
Message-ID: <CAJZ5v0i0NzJfRuqcuJQC3J5moaEikoRusquCybAz0T8dMy8gCw@mail.gmail.com>
Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors
 based on the Zen microarchitecture
To: Borislav Petkov <bp@alien8.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Peter Zijlstra <peterz@infradead.org>, 
	K Prateek Nayak <kprateek.nayak@amd.com>, 
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Len Brown <lenb@kernel.org>, 
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>, Linux PM <linux-pm@vger.kernel.org>, 
	Dave Hansen <dave.hansen@linux.intel.com>, Thomas Gleixner <tglx@linutronix.de>, andi@lisas.de, 
	Pu Wen <puwen@hygon.cn>, Mario Limonciello <mario.limonciello@amd.com>, 
	"Zhang, Rui" <rui.zhang@intel.com>, "Guilherme G. Piccoli" <gpiccoli@igalia.com>, 
	Daniel Lezcano <daniel.lezcano@linaro.org>, ananth.narayan@amd.com, gautham.shenoy@amd.com, 
	Calvin Ong <calvin.ong@amd.com>, Stable <stable@vger.kernel.org>, regressions@lists.linux.dev
Content-Type: text/plain; charset="UTF-8"

On Thu, Sep 22, 2022 at 5:36 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Thu, Sep 22, 2022 at 05:21:21PM +0200, Rafael J. Wysocki wrote:
> > Well, it can be forced to use ACPI idle instead.
>
> Yeah, I did that earlier. The dummy IO read in question costs ~3K on
> average on my Coffeelake box here.

Well, that's the cost of forcing something non-default.