There may be cases where the guest does not want the avail queue interrupt, even when it's empty. For the virtio-net case, the guest may use a different buffering scheme or decide polling for used buffers is more efficient. This can be accomplished by simply checking for whether the guest has acknowledged the existing notify on empty flag.
Signed-off-by: Alex Williamson <[email protected]> --- hw/virtio.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/hw/virtio.c b/hw/virtio.c index b94ab0f..08ea16d 100644 --- a/hw/virtio.c +++ b/hw/virtio.c @@ -726,9 +726,10 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size, void virtio_notify(VirtIODevice *vdev, VirtQueue *vq) { - /* Always notify when queue is empty */ - if ((vq->inuse || vring_avail_idx(vq) != vq->last_avail_idx) && - (vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT)) + /* Always notify when queue is empty (when feature acknowledge) */ + if ((vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT) && + (!(vdev->features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) || + (vq->inuse || vring_avail_idx(vq) != vq->last_avail_idx))) return; vdev->isr |= 0x01; -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
