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

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Message-ID: <87lguk6sjk.fsf@vitty.brq.redhat.com>
Date:   Mon, 09 Jan 2017 18:40:15 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
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

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...

-- 
  Vitaly