From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: Is ntpd in guest necessary? Date: Mon, 17 Nov 2008 12:42:07 +0300 Message-ID: <49213C6F.4050502@msgid.tls.msk.ru> References: <491C4E39.6030300@msgid.tls.msk.ru> <49202DE4.3030801@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit To: "kvm@vger.kernel.org" Return-path: Received: from hobbit.corpit.ru ([81.13.33.150]:22017 "EHLO hobbit.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbYKQJmM (ORCPT ); Mon, 17 Nov 2008 04:42:12 -0500 Received: from [192.168.1.200] (mjt.ppp.tls.msk.ru [192.168.1.200]) by hobbit.corpit.ru (Postfix) with ESMTP id AF60C1967C for ; Mon, 17 Nov 2008 12:42:08 +0300 (MSK) (envelope-from mjt@tls.msk.ru) In-Reply-To: <49202DE4.3030801@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Michael Tokarev wrote: >> A question that I asked on irc many times, >> but got no answer.. >> >> Giving guest linux with CONFIG_KVM_TIME set, >> is it necessary to run ntpd in it for accurate >> time, or ntpd on host is sufficient? >> >> And the same, but without CONFIG_KVM_TIME ? > > In theory, CONFIG_KVM_CLOCK should avoid the need for ntp. Let us know > if you get different results. Well. The question was not come from nowhere. It *seems* like it is working, but somewhat.. strange. I.e., when the time steps on the host (for whatever reason), it stays the same on guests, at least for some time. Later on it syncronizes, *sometimes*, but not always. I tried to reproduce this unsyncronization (hence the delay with replying), but can't do it easily "on demand". Maybe I were just dreaming at the time I saw it, but I don't think so. Or maybe something has changed in recent kernels/kvm so that it does not happen any more. That's why I asked in the first place. In short: with CONFIG_KVM_TIME set, it *seems* to work, but I'm not 100% sure still. The question was if it *supposed* to work in the first place, and you answered that. And withOUT CONFIG_KVM_TIME, it stays unsyncronized. Thanks! /mjt