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

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Date:   Tue, 20 Mar 2018 10:41:49 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Joao Martins <joao.m.martins@...cle.com>
Cc:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        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,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        devel@...ica.org
Subject: Re: [PATCH v3] xen/acpi: upload _PSD info for non Dom0 CPUs too

On Fri, Mar 16, 2018 at 2:57 PM, Joao Martins <joao.m.martins@...cle.com> wrote:
> On 03/15/2018 03:45 PM, Boris Ostrovsky wrote:
>> 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>
>>
> Thanks!
>
> I suppose what's remaining is review (or ack) from ACPI folks on the interface
> changes made to acpi_processor_get_psd().

There you go:

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Do you want to route this via Xen?