linux-kernel - Re: [Xen-devel] [PATCH 3/3] x86/xen: sync the CMOS RTC as well as the Xen wallclock

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Date:	Tue, 14 May 2013 09:28:01 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Jan Beulich <JBeulich@...e.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Thomas Gleixner <tglx@...utronix.de>, xen-devel@...ts.xen.org,
	linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH 3/3] x86/xen: sync the CMOS RTC as well as
 the Xen wallclock

On 05/14/2013 09:24 AM, Konrad Rzeszutek Wilk wrote:
> John Stultz <john.stultz@...aro.org> wrote:
>
>> On 05/14/2013 09:14 AM, Jan Beulich wrote:
>>>>>> On 14.05.13 at 17:59, John Stultz <john.stultz@...aro.org> wrote:
>>>> On 05/14/2013 12:57 AM, Jan Beulich wrote:
>>>>>>>> On 14.05.13 at 02:52, John Stultz <john.stultz@...aro.org>
>> wrote:
>>>>>> Honestly, it seems a little strange to me. If you're running as
>> dom0,
>>>>>> why does HYPERVISOR_dom0_op() not cause the hypervisor to set the
>> cmos
>>>>>> its virtualizing? This seems to mess with the proper
>> virtualization
>>>>>> layering.
>>>>> Thy hypervisor tries to control as little system and peripheral
>> devices
>>>>> as possible, and the CMOS (including the clock) is among those not
>>>>> controlled by it, but by Dom0.
>>>> Huh. So what does calling HYPERVISOR_dom0_op do then?
>>> Here it merely tells the hypervisor that the wall clock changed (so
>>> it can propagate this on to DomU-s).
>> Ok, I appreciate the explanation. Still waiting for acks on this one.
>>
>> thanks
>> -john
> Acked-by: Konrad Rzeszutek Wilk
>
> Or Reviewed-by. Or John if you would like I can carry this in my branch for Linus.
>
> Thought it might make sense to add the comment from Jan about the CMOS and the follow up explanation.
I'm fine queuing it, but yea, the commit will need some more context.

thanks
-john

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