From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH 0/3] xen: fix various wallclock problems Date: Fri, 12 Oct 2012 17:25:06 +0100 Message-ID: <50784462.3060203@citrix.com> References: <1350046634-2462-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1350046634-2462-1-git-send-email-david.vrabel@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: David Vrabel Cc: Konrad Rzeszutek Wilk , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 12/10/12 13:57, David Vrabel wrote: > This series (with some toolstack updates) corrects a number of cases > where a guest can see an incorrect wallclock time. > > 1. Systems with NTP won't periodically synchronize the hardware RTC so > the wallclock may be incorrect after a reboot. > > 2. The wallclock is always ~500 ms behind the correct time. > > 3. If the system time was stepped and NTP isn't synchronized yet, the > wallclock will still have the incorrect time. The fix for this > requires the toolstack to synchronize the wallclock -- patch #3 > provides the mechanism for this. These tables should help. Before: | Updates Process | System Time? Xen Wallclock? Hardware Clock? ------------------------------------------------------------- date -s | X hwclock -w | X ntpd | X X[*] ntpdate | X After this (and the toolstack) patches: | Updates Process | System Time? Xen Wallclock? Hardware Clock? ------------------------------------------------------------- date -s | X hwclock -w | X ntpd | X X[*] X[*] ntpdate | X xen-wallclock | X [*] every 11 minutes. David