linux-kernel - Re: [PATCH v3] xen/acpi: upload

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Message-ID: <bbf536dc-3c3d-8a25-47e8-7fd52850835d@oracle.com>
Date:   Thu, 15 Mar 2018 11:45:01 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Joao Martins <joao.m.martins@...cle.com>,
        linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Erik Schmauss <erik.schmauss@...el.com>,
        xen-devel@...ts.xenproject.org, linux-acpi@...r.kernel.org,
        devel@...ica.org
Subject: Re: [PATCH v3] xen/acpi: upload _PSD info for non Dom0 CPUs too

On 03/15/2018 10:22 AM, Joao Martins wrote:
> All uploaded PM data from non-dom0 CPUs takes the info from vCPU 0 and
> changing only the acpi_id. For processors which P-state coordination type
> is HW_ALL (0xFD) it is OK to upload bogus P-state dependency information
> (_PSD), because Xen will ignore any cpufreq domains created for past CPUs.
>
> Albeit for platforms which expose coordination types as SW_ANY or SW_ALL,
> this will have some unintended side effects. Effectively, it will look at
> the P-state domain existence and *if it already exists* it will skip the
> acpi-cpufreq initialization and thus inherit the policy from the first CPU
> in the cpufreq domain. This will finally lead to the original cpu not
> changing target freq to P0 other than the first in the domain. Which will
> make turbo boost not getting enabled (e.g. for 'performance' governor) for
> all cpus.
>
> This patch fixes that, by also evaluating _PSD when we enumerate all ACPI
> processors and thus always uploading the correct info to Xen. We export
> acpi_processor_get_psd() for that this purpose, but change signature
> to not assume an existent of acpi_processor given that ACPI isn't creating
> an acpi_processor for non-dom0 CPUs.
>
> Signed-off-by: Joao Martins <joao.m.martins@...cle.com>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>