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Date: Fri, 08 Mar 2013 10:22:36 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 3/9] dataplane: remove EventPoll in favor
 of AioContext
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To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, Dominik Dingel <dingel@linux.vnet.ibm.com>, Jens Freimann <jfrei@linux.vnet.ibm.com>, Stefan Hajnoczi <stefanha@redhat.com>, Cornelia Huck <cornelia.huck@de.ibm.com>

Il 08/03/2013 09:37, Christian Borntraeger ha scritto:
> +    if (assign) {
> +        int r = event_notifier_init(notifier, 0);
> +
> +        if (r < 0) {
> +            return r;
> +        }
> +        virtio_queue_set_guest_notifier_fd_handler(vq, true, with_irqfd);

Perhaps you can simply hard-code with_irqfd to false in this call to
virtio_queue_set_guest_notifier_fd_handler and the one below?  Then the
guest notifier will be emulated in userspace and processed via
vdev->binding->notify.

You will not need to overwrite the EventNotifier which is IMO a pretty
ufly violation of encapsulation. :)

Paolo

> +        /* We do not support irqfd for classic I/O interrupts, because the
> +         * classic interrupts are intermixed with the subchannel status, that
> +         * is queried with test subchannel. We want to use vhost, though.
> +         * Lets make sure to have vhost running and wire up the irq fd to 
> +         * land in qemu (and only the irq fd) in this code.
> +         */
> +        if (dev->vdev->guest_notifier_mask) {
> +            dev->vdev->guest_notifier_mask(dev->vdev, n, false);
> +        }
> +        /* get lost events and re-inject */
> +        if (dev->vdev->guest_notifier_pending &&
> +            dev->vdev->guest_notifier_pending(dev->vdev, n)) {
> +            event_notifier_set(notifier);
> +        }
> +    } else {
> +        if (dev->vdev->guest_notifier_mask) {
> +            dev->vdev->guest_notifier_mask(dev->vdev, n, true);
> +        }
> +        virtio_queue_set_guest_notifier_fd_handler(vq, false, with_irqfd);
> +        event_notifier_cleanup(notifier);