linux-kernel - Re: [PATCH 3/4] hv_util: use do_adjtimex() to update system time

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Message-ID: <20170109095827.0cc364ad@xeon-e3>
Date:   Mon, 9 Jan 2017 09:58:27 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     "Alex Ng \(LIS\)" <alexng@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        John Stultz <john.stultz@...aro.org>,
        "devel\@linuxdriverproject.org" <devel@...uxdriverproject.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/4] hv_util: use do_adjtimex() to update system time

On Mon, 09 Jan 2017 18:40:15 +0100
Vitaly Kuznetsov <vkuznets@...hat.com> wrote:

> Stephen Hemminger <stephen@...workplumber.org> writes:
> 
> > An alternative would be for hyper-v util to provide a clocksource device and
> > let NTP manage the adjustment. The advantage of this would be HV util not fighting
> > with NTP, and using standard API's. The downside would be the complexity of configuring
> > NTP, and difficulty of writing a clock source pseudo device.  
> 
> Yes, I see this option. But as I wrote to John I'm afraid we'll have to
> come up with a custom interface from hv_util to userspace which no NTP
> server will want to support (because, first of all, it's not about
> 'network time' any more). We can write our own daemon which will read
> from this interface and do adjtimex but in this case I don't see much
> value in this data traveling from kernel to userspace and back...
> 

Master NTP servers are connected to authoritative clock sources. I have no idea how
that is configured, but it should be possible.