[dpdk-dev] Question about vhost user interrupt mode

[Yifeng Sun]

Hi all,

Right now on OVS, dpdkvhostuser can only run in polling mode (please
correct me if I am wrong). We are trying to enable interrupt mode of
dpdkvhostuser type port on OVS. We found that, with changes below, OVS
can poll&block on exposed kickfd and vhostuser is working under
interrupt mode without consuming 2 CPUs.

My question is, is this the correct direction to do so, or is there a
better way? Thanks!

--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -318,7 +318,6 @@ struct vring_packed_desc_event {
                                (1ULL << VIRTIO_NET_F_GUEST_UFO) | \
                                (1ULL << VIRTIO_NET_F_GUEST_ECN) | \
                                (1ULL << VIRTIO_RING_F_INDIRECT_DESC) | \
-                               (1ULL << VIRTIO_RING_F_EVENT_IDX) | \
                                (1ULL << VIRTIO_NET_F_MTU)  | \
                                (1ULL << VIRTIO_F_IN_ORDER) | \
                                (1ULL << VIRTIO_F_IOMMU_PLATFORM) | \

+int rte_vhost_get_kickfd(int vid, uint16_t queue_id)
+{
+       struct virtio_net *dev;
+       struct vhost_virtqueue *vq;
+
+       dev = get_device(vid);
+       if (!dev)
+               return -1;
+
+       if (unlikely(!(dev->flags & VIRTIO_DEV_BUILTIN_VIRTIO_NET))) {
+               //  vhost net backend is disabled.
+               return -1;
+       }
+
+       if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->nr_vring))) {
+               return -1;
+       }
+
+       vq = dev->virtqueue[queue_id];
+       // XXX lock?
+       return vq->kickfd;
+}

Best,
Yifeng Sun