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Date:   Thu, 22 Sep 2022 09:36:05 -0700
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Subject: Re: [PATCH] ACPI: processor_idle: Skip dummy wait for processors
 based on the Zen microarchitecture
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To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Borislav Petkov <bp@alien8.de>
Cc:     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
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From:   Dave Hansen <dave.hansen@intel.com>
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On 9/22/22 08:53, Rafael J. Wysocki wrote:
> 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.

Just to be clear: The _original_ AMD Zen problem that this thread is
addressing is from a *default* configuration, right?  It isn't that
someone overrode the idle defaults?