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 <mst@xxxxxxxxxx>
---
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 majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
