Re: [Qemu-devel] [PATCH 2/7] Replace VMSTOP macros with a proper QemuState type

[Luiz Capitulino]

On Mon, 08 Aug 2011 17:27:24 +0300
Avi Kivity <address@hidden> wrote:

> On 08/08/2011 05:06 PM, Luiz Capitulino wrote:
> > >
> > >  This is why I suggested a reference count.  In this case, we can always
> > >  stop the guest "twice", because we don't lost information when we resume.
> >
> > I could give it a try in the near future, as I really think it's independent
> > from this series, but I still don't understand what can stop an already 
> > stopped
> > VM besides the user. This is a real question, is it really possible?
> >
> > If only the user can do that, then the refcount is overkill as just 
> > returning
> > an error will do it.
> 
> Most of the reasons in QemuState are asynchronous and can happen at any 
> time while the guest is running.  Because they're asynchronous, they can 
> trigger before a monitor stop is issued but caught after it is processed.
> 
> We could possibly synchronize during user stop, but that lets us capture 
> only the first non-user reason.

Isn't it good enough?

Another question: do you think that this problem is so relevant that we
should include the fix in the first merge?

> 
> And even if we return an error, that only pushes the refcounting to the 
> user; you probably don't want to return a "vm is already stopped" error 
> to the user, he'll just ask "why are you telling me that".
>