[PATCH 17/18] virtio-net: vhost control virtqueue support

[Jason Wang]

This patch implements the control virtqueue support for vhost. This
requires virtio-net to figure out the datapath queue pairs and control
virtqueue via is_datapath and pass the number of those two types
of virtqueues to vhost_net_start()/vhost_net_stop().

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 hw/net/virtio-net.c            | 20 +++++++++++++++++---
 include/hw/virtio/virtio-net.h |  1 +
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 36bd197087..5074b521cf 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -244,6 +244,7 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t 
status)
     VirtIODevice *vdev = VIRTIO_DEVICE(n);
     NetClientState *nc = qemu_get_queue(n->nic);
     int qps = n->multiqueue ? n->max_qps : 1;
+    int cvq = n->max_ncs - n->max_qps;
 
     if (!get_vhost_net(nc->peer)) {
         return;
@@ -285,14 +286,14 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t 
status)
         }
 
         n->vhost_started = 1;
-        r = vhost_net_start(vdev, n->nic->ncs, qps, 0);
+        r = vhost_net_start(vdev, n->nic->ncs, qps, cvq);
         if (r < 0) {
             error_report("unable to start vhost net: %d: "
                          "falling back on userspace virtio", -r);
             n->vhost_started = 0;
         }
     } else {
-        vhost_net_stop(vdev, n->nic->ncs, qps, 0);
+        vhost_net_stop(vdev, n->nic->ncs, qps, cvq);
         n->vhost_started = 0;
     }
 }
@@ -3367,7 +3368,20 @@ static void virtio_net_device_realize(DeviceState *dev, 
Error **errp)
         return;
     }
 
-    n->max_qps = MAX(n->nic_conf.peers.queues, 1);
+    n->max_ncs = MAX(n->nic_conf.peers.queues, 1);
+
+    /* Figure out the datapath queue pairs since the bakcend could
+     * provide control queue via peers as well.
+     */
+    if (n->nic_conf.peers.queues) {
+        for (i = 0; i < n->max_ncs; i++) {
+            if (n->nic_conf.peers.ncs[i]->is_datapath) {
+                ++n->max_qps;
+            }
+        }
+    }
+    n->max_qps = MAX(n->max_qps, 1);
+
     if (n->max_qps * 2 + 1 > VIRTIO_QUEUE_MAX) {
         error_setg(errp, "Invalid number of qps (= %" PRIu32 "), "
                    "must be a positive integer less than %d.",
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index a9b6dc252e..ed4659c189 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -194,6 +194,7 @@ struct VirtIONet {
     NICConf nic_conf;
     DeviceState *qdev;
     int multiqueue;
+    uint16_t max_ncs;
     uint16_t max_qps;
     uint16_t curr_qps;
     size_t config_size;
-- 
2.25.1