[Xen-users] Re: domu's time is frozen after change dom0's time backward

["Hongming Xiao" <xiaohm@xxxxxxxxx>]

ooops, forgot to provide OS and xen version info.

When test, ntpd was not running.
OS: CentOS 5.2 (both domU and dom0)
Output of "xm info"

xm info
host                   : 302472-lab1.hq.avaya.com
release                : 2.6.18-92.1.6.el5xen
version                : #1 SMP Wed Jun 25 14:13:10 EDT 2008
machine                : x86_64
nr_cpus                : 8
nr_nodes               : 1
sockets_per_node       : 2
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2327
hw_caps                :
bfebfbff:20100800:00000000:00000140:000ce3bd:00000000:0

                                        0000001
total_memory           : 6138
free_memory            : 1
node_to_cpu            : node0:0-7
xen_major              : 3
xen_minor              : 1
xen_extra              : .2-92.1.6.el5
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x

86_32p hvm-3.0-x86_64
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
cc_compiler            : gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)
cc_compile_by          : mockbuild
cc_compile_domain      : centos.org
cc_compile_date        : Wed Jun 25 13:39:56 EDT 2008
xend_config_format     : 2

On Thu, Sep 25, 2008 at 6:13 PM, Hongming Xiao <xiaohm@xxxxxxxxx> wrote:
> All,
>
> Hope this is the right list to post my question.
>
> I noticed that once I changed dom0's time backward, domU's time will
> be frozen. Here is the step to reproduce the problem.
>
> a) sync domU's time with dom0 by running following command in domU
>
> # echo 0 > /proc/sys/xen/independent_wallclock
>
> b) Verify domU's time is synced to dom0's
>
> In dom0:
> # date
> Thu Sep 25 12:10:03 EDT 2008
>
> In domU:
> # date
> Thu Sep 25 12:10:04 EDT 2008
>
> c) Change dom0's time backward for 1 hour
>
> In dom0:
> # date 0925110000
>
> In dom0:
> # daten
> Thu Sep 25 11:00:02 EDT 2008
>
> d) Then, domU's time is frozen at the time we made change to dom0's time.
>
> In domU:
> # date
> Thu Sep 25 12:11:00 EDT 2008
> # date
> Thu Sep 25 12:11:00 EDT 2008
> # date
> Thu Sep 25 12:11:00 EDT 2008
> ....
>
> domU's time can be unfrozen by making domU's time older than dom0's,
> no matter by changing dom0 or domU's time.
>
> In domU: (change domU's time backward)
> # date 0925100000
>
> In domU:
> # date
> Thu Sep 25 11:01:00 EDT 2008
>
>
> Question:
>
> Appearently, Xen will stop syncing domU's time if dom0's time is older
> than domU's.  Is it possible to configure Xen to let it sync domU's
> time to dom0's (not matter what dom0's time is)?
>
> Thanks in advance,
> Bill Wei
>

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