Re: [Qemu-devel] [PATCH V2] balloon: Don't try fetching info if machine is stopped

[Anthony Liguori]

On 08/26/2010 03:14 AM, Daniel P. Berrange wrote:
> On Thu, Aug 26, 2010 at 10:05:44AM +0200, Paolo Bonzini wrote:
>    
> > On 08/26/2010 08:05 AM, Amit Shah wrote:
> >      
> > > This is what I have currently. It would need some timer handling in
> > > the save/load case as well, right?
> > >        
> > When loading you won't have any pending "info balloon" command, so I
> > think the timer need not be preserved across migration.
> >
> > Also, 5 seconds for a stopped guest is actually a lot, so maybe Amit's
> > original patch or a variant thereof would make sense anyway.
> >      
> We should have a combination of both. If we know the guest is stopped
> we should return immediately, otherwise we should use the timer as a
> way to cope with a crashed/evil guest.
>    

Stopped doesn't necessarily mean that it's permanently stopped or even 
that a user has stopped it.

We stop a guest during live migration and in some other cases (like on 
disk error).

Returning immediately is an optimization on something that should be a 
proper fix.  Otherwise, you have a guest initiated DoS attack on 
management tools.

Regards,

Anthony Liguori

> Daniel
>