[PATCH V4 09/10] virtio-net: vhost control virtqueue support

[Jason Wang <jasowang@redhat.com>]

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>
Message-Id: <20210907090322.1756-10-jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/net/vhost_net.c             |  2 +-
 hw/net/virtio-net.c            | 23 +++++++++++++++++++----
 include/hw/virtio/virtio-net.h |  1 +
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 3aabab06ea..0d888f29a6 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -326,7 +326,7 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
     VirtIONet *n = VIRTIO_NET(dev);
     int nvhosts = data_queue_pairs + cvq;
     struct vhost_net *net;
-    int r, e, i, last_index = data_qps * 2;
+    int r, e, i, last_index = data_queue_pairs * 2;
     NetClientState *peer;
 
     if (!cvq) {
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 2ade019b22..57a0cbc6cd 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 queue_pairs = n->multiqueue ? n->max_queue_pairs : 1;
+    int cvq = n->max_ncs - n->max_queue_pairs;
 
     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, queue_pairs, 0);
+        r = vhost_net_start(vdev, n->nic->ncs, queue_pairs, 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, queue_pairs, 0);
+        vhost_net_stop(vdev, n->nic->ncs, queue_pairs, cvq);
         n->vhost_started = 0;
     }
 }
@@ -3393,9 +3394,23 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
         return;
     }
 
-    n->max_queue_pairs = 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 backend 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_queue_pairs;
+            }
+        }
+    }
+    n->max_queue_pairs = MAX(n->max_queue_pairs, 1);
+
     if (n->max_queue_pairs * 2 + 1 > VIRTIO_QUEUE_MAX) {
-        error_setg(errp, "Invalid number of queue_pairs (= %" PRIu32 "), "
+        error_setg(errp, "Invalid number of queue pairs (= %" PRIu32 "), "
                    "must be a positive integer less than %d.",
                    n->max_queue_pairs, (VIRTIO_QUEUE_MAX - 1) / 2);
         virtio_cleanup(vdev);
diff --git a/include/hw/virtio/virtio-net.h b/include/hw/virtio/virtio-net.h
index 71cbdc26d7..08ee6dea39 100644
--- a/include/hw/virtio/virtio-net.h
+++ b/include/hw/virtio/virtio-net.h
@@ -196,6 +196,7 @@ struct VirtIONet {
     int multiqueue;
     uint16_t max_queue_pairs;
     uint16_t curr_queue_pairs;
+    uint16_t max_ncs;
     size_t config_size;
     char *netclient_name;
     char *netclient_type;
-- 
2.25.1