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

[Avi Kivity]

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.

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".

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