Re: [KVM PATCH v2 2/2] kvm: add support for irqfd via eventfd-notification interface

Avi Kivity
2009-04-28T11:00:27Z

Gregory Haskins wrote:

>> But eventfd_signal basically marries us to eventfd.
>>
>
> Well, only if we expect the fd to have eventfd semantics. There are
> advantages to doing so, as we have discussed, because things like AIO
> can polymorhpically signal an interrupt without even knowing whats
> behind the eventfd. But this isn't a strict requirement to support
> AIO. Really all we need is a way for both kernel and userspace to
> signal. Perhaps I should export an "irqfd_signal()" function from kvm,
> which today will map to eventfd_signal(), and tomorrow to ??. I don't
> think using f_ops->write() is an option for in-kernel signaling, so we
> need some kind of interface here.
>
> Does that sound reasonable?
>

irqfd_signal() ties the user of irqfd to kvm. I want this user to be
independent of kvm; it should work with eventfd, kvm's eventfd lookalike
(if we move away from eventfd) or pipes.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.