[PATCH V4 08/10] vhost: record the last virtqueue index for the virtio device

[Jason Wang <jasowang@redhat.com>]

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 <jasowang@redhat.com>
Message-Id: <20210907090322.1756-9-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        | 12 +++++++++---
 include/hw/virtio/vhost.h |  2 ++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 2b594b4642..3aabab06ea 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -231,9 +231,11 @@ fail:
     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
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 1a9fc65089..3fa0b554ef 100644
--- a/include/hw/virtio/vhost.h
+++ b/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;
-- 
2.25.1