vhost-net: save & restore vring enable state

A driver may change the vring enable state at run time but vhost-user
backend may not be present (a contrived example is when the backend is
disconnected and the device is reconfigured after driver rebinding)

Restore the vring state when the vhost-user backend is started, so it
can process the ring.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Victor Kaplansky <victork@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index b28881ffe3..50f4dcd655 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -329,6 +329,15 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
         if (r < 0) {
             goto err_start;
         }
+
+        if (ncs[i].peer->vring_enable) {
+            /* restore vring enable state */
+            r = vhost_set_vring_enable(ncs[i].peer, ncs[i].peer->vring_enable);
+
+            if (r < 0) {
+                goto err_start;
+            }
+        }
     }
 
     return 0;
@@ -422,6 +431,8 @@ int vhost_set_vring_enable(NetClientState *nc, int enable)
     VHostNetState *net = get_vhost_net(nc);
     const VhostOps *vhost_ops;
 
+    nc->vring_enable = enable;
+
     if (!net) {
         return 0;
     }
diff --git a/include/net/net.h b/include/net/net.h
index a69e382ba7..a5c5095154 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -99,6 +99,7 @@ struct NetClientState {
     NetClientDestructor *destructor;
     unsigned int queue_index;
     unsigned rxfilter_notify_enabled:1;
+    int vring_enable;
     QTAILQ_HEAD(NetFilterHead, NetFilterState) filters;
 };