linux-kernel - RE: [PATCH] Drivers: hv: util: Implement Time Synchronization using host time sample

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Date:	Tue, 23 Sep 2014 09:47:59 +0000
From:	Thomas Shao <huishao@...rosoft.com>
To:	Olaf Hering <olaf@...fle.de>
CC:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	"apw@...onical.com" <apw@...onical.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"KY Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: RE: [PATCH] Drivers: hv: util: Implement Time Synchronization using
 host time sample


> -----Original Message-----
> From: Olaf Hering [mailto:olaf@...fle.de]
> Sent: Tuesday, September 23, 2014 3:56 PM
> To: Thomas Shao
> Cc: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> driverdev-devel@...uxdriverproject.org; apw@...onical.com;
> jasowang@...hat.com; KY Srinivasan; Haiyang Zhang
> Subject: Re: [PATCH] Drivers: hv: util: Implement Time Synchronization using
> host time sample
> 
> On Tue, Sep 23, Thomas Shao wrote:
> 
> > In current hyper-v time sync service,it only gets the initial clock
> > time from the host. It didn't process the following time samples. This
> > change introduced a module parameter called host_time_sync. If it is
> > set to true, the guest will periodically sychronize it's time with the
> > host clock using host time sample. By default it is disabled, because
> > we still recommend user to configure NTP for time synchronization.
> 
> Is that new knob a temporary thing to aid testing and development?
> Because once it sneaks in it becomes some sort of ABIT.
> So if the outcome of all that is that 'sync with host every once in a while' will be
> the default, the new knob is not required.
> 

Hi Olaf, 
If the guest is configured with other time sync source, like NTP, we don't want the 
guest to periodically sync with host. This feature is useful when the guest didn't have
Internet connection to setup NTP. So the new knob is to allow users to only turn on the
host-guest sync when they need.

Regards
Thomas

> Olaf