libvirt users - Apr 2014 - Re: libvirt-users Digest, Vol 52, Issue 39

On Sun, Apr 27, 2014 at 5:00 PM, <libvirt-users-request@redhat.com> wrote:
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> Today's Topics:
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>    1. Ability of a VM to detect Libvirt events. (Taimur Al Said)
>    2. Re: Ability of a VM to detect Libvirt events. (Brian Rak)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 26 Apr 2014 22:46:30 +0100
> From: Taimur Al Said <alsaidts@gmail.com>
> To: libvirt-users@redhat.com
> Subject: [libvirt-users] Ability of a VM to detect Libvirt events.
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YZgbogNqQLQPxOJfRXshGcqosgDmPKg@mail.gmail.com>
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> Hi there,
>
> Let's assume a libvirt event occurred on a VM, i.e an event like pause
VM
> or reboot VM or any other libvirt event. Can the VM determine that such
> event was originated by libvirt? ---or in a more general term by the
> hypervisor? If yes, how can this be done in theory?
>
> Thanks in advance,
>
> Regards,
> Taimur
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> Message: 2
> Date: Sat, 26 Apr 2014 18:46:42 -0400
> From: Brian Rak <brak@gameservers.com>
> To: libvirt-users@redhat.com
> Subject: Re: [libvirt-users] Ability of a VM to detect Libvirt events.
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> How are you thinking that a VM would be paused/rebooted via something
> other then the hypervisor?
>
> On 4/26/2014 5:46 PM, Taimur Al Said wrote:
> > Hi there,
> >
> > Let's assume a libvirt event occurred on a VM, i.e an event like
pause
> > VM or reboot VM or any other libvirt event. Can the VM determine that
> > such event was originated by libvirt? ---or in a more general term by
> > the hypervisor? If yes, how can this be done in theory?
> >
> > Thanks in advance,
> >
> > Regards,
> > Taimur
> >
> >
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> End of libvirt-users Digest, Vol 52, Issue 39
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Thanks,
I guess my query was clear. However, I'll make it clearer.
I know that the such events are caused by the hypervisor. Either directly
or using tools such as Libvirt. The question is: can such events be
detectable from the VM level? In another word, can the VM tell if it was
being paused/rebooted/migrated/etc?

Best regards,
Taimur

On 04/27/2014 10:42 AM, Taimur Al Said wrote:
> On Sun, Apr 27, 2014 at 5:00 PM, <libvirt-users-request@redhat.com>
wrote:
> 
>> Send libvirt-users mailing list submissions to
>>         libvirt-users@redhat.com
>>
>> To subscribe or unsubscribe via the World Wide Web, visit
>>         https://www.redhat.com/mailman/listinfo/libvirt-users
>> or, via email, send a message with subject or body 'help' to
>>         libvirt-users-request@redhat.com
>>
>> You can reach the person managing the list at
>>         libvirt-users-owner@redhat.com
>>
>> When replying, please edit your Subject line so it is more specific
>> than "Re: Contents of libvirt-users digest..."
Please follow the advice that you were given, by NOT replying directly
to an entire digest message.

> I guess my query was clear. However, I'll make it clearer.
> I know that the such events are caused by the hypervisor. Either directly
> or using tools such as Libvirt. The question is: can such events be
> detectable from the VM level? In another word, can the VM tell if it was
> being paused/rebooted/migrated/etc?
If you want to inform the VM that it has been paused, then it is up to
you to wire up that communication channel.  For example, the qemu guest
agent includes a set-time command that allows a hypervisor to tell the
guest to recheck its notion of the current time, useful for getting the
guest to sync back to the current time after the hypervisor has resumed
the guest from sleep.  But it still leaves the burden on the management
application to invoke this guest-agent command at the right sequence
points; it's not something that libvirt will automate.

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