linux-kernel - Re: [PATCH] turbostat: Running on virtual machine is not supported

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Message-ID: <8aa1f7ec-1d21-f027-f4c4-7c3d8e88b8d2@redhat.com>
Date:   Fri, 28 Jul 2017 07:54:27 -0400
From:   Prarit Bhargava <prarit@...hat.com>
To:     Len Brown <lenb@...nel.org>,
        Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] turbostat: Running on virtual machine is not supported



On 07/26/2017 11:09 PM, Len Brown wrote:
> Henrique,
> 
> I like your suggestion, thanks!
> 
> BTW. let's discuss (and patch) turbostat on linux-pm, rather than on lkml.
> 
> thanks,
> -Len
> 
> 
> On Tue, Jul 25, 2017 at 11:59 AM, Henrique de Moraes Holschuh
> <hmh@....eng.br> wrote:
>> On Tue, 25 Jul 2017, Prarit Bhargava wrote:
>>> A common way of determining if the system is a virtual machine is to
>>> search /proc/cpuinfo flags entry for "hypervisor".  turbostat must output
>>> a proper error message when found.
>>
>> Maybe you could output that message only if it fails to both use
>> /dev/msr and perf *and* it is under a virtual machine?  That would have
>> better forward compatibility, maybe someday /dev/msr or perf will work
>> inside a VM for what turbostat needs...

To answer Len's previous question: I was wrong in my description.  perf does
work (mostly) under virt.  So this would only be for the msr code.  I'll post a
v2 to linux-pm, and take Henrique's suggestion to only trigger on an msr read
failure.

P.

>>
>> --
>>   Henrique Holschuh
> 
> 
>