Re: [KVM PATCH v4 2/2] kvm: add support for irqfd via eventfd-notification interface

Davide Libenzi
2009-05-07T01:39:43Z

On Wed, 6 May 2009, Gregory Haskins wrote:

> I think we are ok in this regard (at least in v5) without the callback.
> kvm holds irqfd, which holds eventfd. In a normal situation, we will
> have eventfd with 2 references. If userspace closes the eventfd, it
> will drop 1 of the 2 eventfd file references, but the object should
> remain intact as long as kvm still holds it as well. When the kvm-fd is
> released, we will then decouple from the eventfd->wqh and drop the last
> fput(), officially freeing it.
>
> Likewise, if kvm is closed before the eventfd, we will simply decouple
> from the wqh and fput(eventfd), leaving the last reference held by
> userspace until it closes as well.
>
> Let me know if you see any holes in that.

Looks OK, modulo my knowledge of KVM internals.

- Davide