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

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Message-ID: <32efe991-ac51-410b-aead-68a480e628d6@email.android.com>
Date:	Tue, 14 May 2013 12:24:57 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	John Stultz <john.stultz@...aro.org>,
	Jan Beulich <JBeulich@...e.com>
CC:	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

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.
-- 
Sent from my Android phone. Please excuse my brevity.
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