Re: [Qemu-devel] [RFC 0/5]: QMP: Introduce GUEST_MEDIUM_EJECT & BLOCK_MEDIUM_CHANGED

[Paolo Bonzini]

On 02/10/2012 08:39 PM, Paolo Bonzini wrote:
> > >  1. added commands blockdev-tray-open, blockdev-tray-close,
> > > blockdev-medium-insert,
> > >     blockdev-medium-remove
>
> I think this slightly overengineering.  eject and change work well
> enough, we do not need blockdev-medium-insert and blockdev-medium-remove
> (yet).  Of course there can be a new API, just nothing user-visible.
>
> > >  2. added the events: BLOCK_TRAY_OPEN, BLOCK_TRAY_CLOSE,
> > > BLOCK_MEDIUM_INSERTED
> > >     BLOCK_MEDIUM_REMOVED, which would be emitted when the relating
> > > command is issued
> > >     (maybe the events could just be BLOCK_TRAY_CHANGED &
> > > BLOCK_MEDIUM_CHANGED)
>
> Or even just one event with two boolean arguments.
>
> Looks slightly less clean, but it has an advantage: a guest that sends
> "eject" can wait for an event and will know whether the eject command
> was really executed (tray = open, medium = none) or just an eject
> request was obeyed by the guest (tray = open, medium = present).
>
> > > Now, maybe the guest eject could also emit BLOCK_TRAY_OPEN &
> > > BLOCK_TRAY_CLOSE. Then
> > > I think this is a complete solution.
>
> Yes.

Hmm... I don't know...

The more I think about it, the more I like Luiz's original proposal of 
only signaling guest-initiated ejects.  I won't hold up any other patch 
that works, but I cannot think of something that is as easily usable by 
management in a non-racy way.

Paolo