Add support for the used_event idx feature: when enabling interrupts, publish the current avail index value to the host so that we get interrupts on the next update.
Signed-off-by: Michael S. Tsirkin <[email protected]> --- drivers/virtio/virtio_ring.c | 14 ++++++++++++++ 1 files changed, 14 insertions(+), 0 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 507d6eb..3a3ed75 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -320,6 +320,14 @@ void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) ret = vq->data[i]; detach_buf(vq, i); vq->last_used_idx++; + /* If we expect an interrupt for the next entry, tell host + * by writing event index and flush out the write before + * the read in the next get_buf call. */ + if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) { + vring_used_event(&vq->vring) = vq->last_used_idx; + virtio_mb(); + } + END_USE(vq); return ret; } @@ -341,7 +349,11 @@ bool virtqueue_enable_cb(struct virtqueue *_vq) /* We optimistically turn back on interrupts, then check if there was * more to do. */ + /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to + * either clear the flags bit or point the event index at the next + * entry. Always do both to keep code simple. */ vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; + vring_used_event(&vq->vring) = vq->last_used_idx; virtio_mb(); if (unlikely(more_used(vq))) { END_USE(vq); @@ -468,6 +480,8 @@ void vring_transport_features(struct virtio_device *vdev) break; case VIRTIO_RING_F_INDIRECT_DESC: break; + case VIRTIO_RING_F_USED_EVENT_IDX: + break; default: /* We don't understand this bit. */ clear_bit(i, vdev->features); -- 1.7.5.53.gc233e -- 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
