[fedora-virt] 'eject' on a KVM guest

[Matthew Booth]

On 19/10/09 14:38, Daniel P. Berrange wrote:
> On Mon, Oct 19, 2009 at 09:35:04AM -0400, Cole Robinson wrote:
>> On 10/19/2009 05:47 AM, Matthew Booth wrote:
>>> What does the eject (to eject a CD) command do to a KVM guest? It
>>> succeeds, and the result is that the device can no longer be mounted.
>>> However, looking at the domain XML reveals it hasn't disconnected the
>>> backing file.
>>>
>>> Matt
>>
>> It should be the equivalent of ejecting a CD or floppy on a physical
>> machine.
>>
>> If you do this through libvirt (with the attach-device command and
>> suitable XML string), then the change should be reflected in the XML.
>>
>> If you managed to send a monitor command to the KVM guest that didn't go
>> through libvirt, the change wouldn't be reflected in the domain XML for
>> the majority of operations (media eject included).
>
> I think the problem Matt sees is from running 'eject' inside the guest.
> libvirt will not see that, because KVM has no way to notify us that the
> guest ejected the media.

That's it. Re-reading, that wasn't clear from my original question.

> Fortunately, the new KVM monitor control protocol includes support for
> this notification, so we'll be able to address this limitation in the
> future.

Sounds good. Any idea what the timeframe might be for that?

To put this in context, I was trying to think of an existing way a guest 
can modify its environment. I was thinking that if you configured a boot 
order of cdrom, hd, and attached a custom LiveCD, the LiveCD could do 
its thing and then eject itself, booting from hd next time with no 
administrative intervention. Could that ever work?

Matt
-- 
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

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