From mboxrd@z Thu Jan 1 00:00:00 1970 From: Diana Crisan Subject: Re: HVM Migration of domU on Qemu-upstream DM causes stuck system clock with ACPI Date: Tue, 21 May 2013 12:16:14 +0100 Message-ID: <519B577E.6070200@flexiant.com> References: <1717491994.10371605.1369131737226.JavaMail.root@zimbra002> <519B50C9.1000008@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <519B50C9.1000008@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: Anthony PERARD , George Dunlap , xen-devel@lists.xen.org, Alex Bligh , Konrad Rzeszutek Wilk List-Id: xen-devel@lists.xenproject.org On 21/05/13 11:47, David Vrabel wrote: > On 21/05/13 11:22, Diana Crisan wrote: >> Hello, >> >>> On Mon, May 20, 2013 at 11:38:45PM +0100, Alex Bligh wrote: >>>> Konrad, >>>> >>>> --On 20 May 2013 15:28:52 -0400 Konrad Rzeszutek Wilk >>>> wrote: >>>> >>>>> It was actually David (CC-ing him here). Alex, when you boot the hosts, >>>>> are the RTC times the same? (date?) >>>> I believe they boot with ntpdate and run ntp, so the wallclock times are >>>> the same. I haven't specifically checked the CMOS clock times if that's >>>> what you meant - I'm not even sure how one does that - but I believe >>>> ntp writes to the CMOS RTC these days. >>> 11 minutes after ntpd has started. > NTP updates the persistent clock when it is first synchronized and then > every 11 minutes. > >> I have checked our machines and they aren't running ntpd, but they >> were synchronised with ntpdate. The date command showed the wallclock >> was in sync and clock -r showed the rtc was also in sync. Both cases >> have a delay of at most 1 second. > Running ntpdate does /not/ set the persistent wallclock so the > persistent clock may be incorrect however if the CMOS RTC is correct on > both machines then the persistent clocks will be approximately the same > anyway. > So, you could try the wallclock[1] series but I think it is unlikely to > help here. > > It looks like the guests may not be properly notified of a resume (after > the migration) and therefore are not properly accounting for the step > change in their clock source. This means migrations one way look like > the clock source as stepped backwards and I guess this is confusing the > kernel as the close source is supposed to be monotonic. > > Migrations the other way then work fine as the clock source steps > forwards not backwards. Actually, I have seen the problem replicated when the vm migrates back to the original host ( the one it was started on), as well as on a first migrate. I can confirm I alternated between the hosts on the creation of the vm to ensure I get all the possible scenarios. This was done without re-synchronising the hosts. > Can you restart the hosts say, 5 minutes apart and then see if the > guest's time recovers (without manually setting the time etc.) within ~5 > mins? I restarted the hosts as you asked 5 minutes apart and the wallclocks and the hardware clocks are still in sync without having run any manual update/ ntpdate on the clock. > David > > [1] http://lists.xen.org/archives/html/xen-devel/2013-05/msg01399.html