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Subject: Re: [PATCH v3] xen/acpi: upload _PSD info for non Dom0 CPUs too
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Juergen Gross <jgross@suse.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        Robert Moore <robert.moore@intel.com>,
        Erik Schmauss <erik.schmauss@intel.com>,
        xen-devel@lists.xenproject.org,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        devel@acpica.org
References: <20180315142205.15839-1-joao.m.martins@oracle.com>
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From:   Joao Martins <joao.m.martins@oracle.com>
Message-ID: <5549560b-44ba-8063-de11-2e74b99a3e20@oracle.com>
Date:   Tue, 20 Mar 2018 11:07:51 +0000
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On 03/20/2018 09:41 AM, Rafael J. Wysocki wrote:
> On Fri, Mar 16, 2018 at 2:57 PM, Joao Martins <joao.m.martins@oracle.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@oracle.com>
>>>
>>> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.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@intel.com>
>
Thank you!

> Do you want to route this via Xen?
> 
I suppose that makes sense given that the majority of the change is on xen acpi
processor. But it's ultimately Boris/Juergen call.

	Joao