libvirt users - Oct 2014 - Re: time setting after suspend/resume

On 09/29/2014 02:28 AM, Martin Kletzander wrote:
> On Fri, Sep 26, 2014 at 08:16:25AM +0800, Bill Kenworthy wrote:
>> Hi,
>>     I am using libvirt with qemu/kvm with qemu-guest-agent and
>> suspend/save/resume linux and windows vm's.  Time in Windows gets
>> handled fine with ntp but I can get neither ntp or chrony to sync after
>> resume without manually setting the time close to correct first.
>>
>> Searching has gotten me to the point where I can manually set the time
>> using qemu-guest-agent but I cant figure out how to get libvirt to
>> automaticly trigger this on resume.  I am finding information saying it
>> works but not how, or that its still work in progress and not
>> implemented yet (but patches exist).  Can someone either say "its
not
>> working yet" or explain what I am missing please?
>>
> 
> What version of libvirt are you using?  Since 1.2.5 there's
> virDomainSetTime() API that can do this and since 1.2.8 it's called
> automatically after resume.
Umm, I have a problem with that statement.  Anything that requires guest
interaction (which guest-agent set-time does) must NOT default to being
automatic; it is only safe to enable if explicitly allowed.  What is the
domain XML that must be explicitly set in order to turn on automatic
time-set after resume?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

On Mon, Sep 29, 2014 at 09:19:39AM -0600, Eric Blake
wrote:
>On 09/29/2014 02:28 AM, Martin Kletzander wrote:
>> On Fri, Sep 26, 2014 at 08:16:25AM +0800, Bill Kenworthy wrote:
>>> Hi,
>>>     I am using libvirt with qemu/kvm with qemu-guest-agent and
>>> suspend/save/resume linux and windows vm's.  Time in Windows
gets
>>> handled fine with ntp but I can get neither ntp or chrony to sync
after
>>> resume without manually setting the time close to correct first.
>>>
>>> Searching has gotten me to the point where I can manually set the
time
>>> using qemu-guest-agent but I cant figure out how to get libvirt to
>>> automaticly trigger this on resume.  I am finding information
saying it
>>> works but not how, or that its still work in progress and not
>>> implemented yet (but patches exist).  Can someone either say
"its not
>>> working yet" or explain what I am missing please?
>>>
>>
>> What version of libvirt are you using?  Since 1.2.5 there's
>> virDomainSetTime() API that can do this and since 1.2.8 it's called
>> automatically after resume.
>
>Umm, I have a problem with that statement.  Anything that requires guest
>interaction (which guest-agent set-time does) must NOT default to being
>automatic; it is only safe to enable if explicitly allowed.  What is the
>domain XML that must be explicitly set in order to turn on automatic
>time-set after resume?
>
Oh, sorry, my fault.  I was under the impression that Michal created
the API especially for this purpose, but looking at the code it's not
done automatically.

@Bill: And as Eric said, it makes sense since the communication with
the guest agent is poorly designed.  You probably have to do "resume;
guest-set-time" if you want that yourself.  One other option is to
check your ntp version, configuration and implementation.  Lot of
detail can matter there, but that's out of my reach and the purpose of
this list.

Have a nice day,
Martin

On 10/02/2014 04:01 AM, Martin Kletzander wrote:
>>> What version of libvirt are you using?  Since 1.2.5 there's
>>> virDomainSetTime() API that can do this and since 1.2.8 it's
called
>>> automatically after resume.
>>
>> Umm, I have a problem with that statement.  Anything that requires
guest
>> interaction (which guest-agent set-time does) must NOT default to being
>> automatic; it is only safe to enable if explicitly allowed.  What is
the
>> domain XML that must be explicitly set in order to turn on automatic
>> time-set after resume?
>>
> 
> Oh, sorry, my fault.  I was under the impression that Michal created
> the API especially for this purpose, but looking at the code it's not
> done automatically.
At one point, I seem to recall a proposal of adding an <on_resume> tag
to domain xml that could explicitly request time resync each time the
domain is resumed; but I don't know if anyone implemented it yet.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org