vhost: record the last virtqueue index for the virtio device

This patch introduces a new field in the vhost_dev structure to record
the last virtqueue index for the virtio device. This will be useful
for the vhost backends with 1:N model to start or stop the device
after all the vhost_dev structures were started or stopped.

Signed-off-by: Jason Wang <[email protected]>
Message-Id: <[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>

Author: jasowang

hw/net/vhost_net.c

@@ -231,9 +231,11 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     return NULL;
 }
 
-static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index)
+static void vhost_net_set_vq_index(struct vhost_net *net, int vq_index,
+                                   int last_index)
 {
     net->dev.vq_index = vq_index;
+    net->dev.last_index = last_index;
 }
 
 static int vhost_net_start_one(struct vhost_net *net,
@@ -324,9 +326,13 @@ 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;
+    int r, e, i, last_index = data_qps * 2;
     NetClientState *peer;
 
+    if (!cvq) {
+        last_index -= 1;
+    }
+
     if (!k->set_guest_notifiers) {
         error_report("binding does not support guest notifiers");
         return -ENOSYS;
@@ -341,7 +347,7 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
         }
 
         net = get_vhost_net(peer);
-        vhost_net_set_vq_index(net, i * 2);
+        vhost_net_set_vq_index(net, i * 2, last_index);
 
         /* Suppress the masking guest notifiers on vhost user
          * because vhost user doesn't interrupt masking/unmasking

include/hw/virtio/vhost.h

@@ -74,6 +74,8 @@ struct vhost_dev {
     unsigned int nvqs;
     /* the first virtqueue which would be used by this vhost dev */
     int vq_index;
+    /* the last vq index for the virtio device (not vhost) */
+    int last_index;
     /* if non-zero, minimum required value for max_queues */
     int num_queues;
     uint64_t features;