Re: [Qemu-devel] [PATCH 3/9] dataplane: remove EventPoll in favor of AioContext

[Christian Borntraeger]

On 04/03/13 10:15, Stefan Hajnoczi wrote:
> From: Paolo Bonzini <address@hidden>
> 
> During the review of the dataplane code, the EventPoll API morphed itself
> (not concidentially) into something very very similar to an AioContext.
> Thus, it is trivial to convert virtio-blk-dataplane to use AioContext,
> and a first baby step towards letting dataplane talk directly to the
> QEMU block layer.
> 
> The only interesting note is the value-copy of EventNotifiers.  At least
> in my opinion this is part of the EventNotifier API and is even portable
> to Windows.  Of course, in this case you should not close the notifier's
> underlying file descriptors or handle with event_notifier_cleanup.
> 
> Signed-off-by: Paolo Bonzini <address@hidden>
> Signed-off-by: Stefan Hajnoczi <address@hidden>

Hmm, this broke data plane on our internal notifier prototype code on virtio-ccw
(attached for reference)
[...]


> +    /* Note that these EventNotifiers are assigned by value.  This is
> +     * fine as long as you do not call event_notifier_cleanup on them
> +     * (because you don't own the file descriptor or handle; you just
> +     * use it).
> +     */

And this might be the reason. Currently we only have eventfd to wire up 
guest_to_host notifiers. The host_to_guest notification is not done
via vectors/irqfd, instead we let our qemu transport listen to the irq
eventfd. Worked fine so far with vhost and dataplane without this patch.

Any ideas how to properly enable a transport that has full host notifiers
but only poor mans guest notifiers?

Christian

guest-host-notifiers.patch
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