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 09:17:26 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	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,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	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 09:14 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
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