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

["Hongming Xiao" <xiaohm@xxxxxxxxx>]

Can somebody let me know this is a known issue or my configuration
issue? BTW, I am using full hardware based virtualization. Will it
make any difference?

TIA


On Fri, Sep 26, 2008 at 10:44 AM, Hongming Xiao <xiaohm@xxxxxxxxx> wrote:
> 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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