vhost-user: add VHOST_USER_GET_QUEUE_NUM message

This is for querying how many queues the backend supports if it has mq
support(when VHOST_USER_PROTOCOL_F_MQ flag is set from the quried
protocol features).

vhost_net_get_max_queues() is the interface to export that value, and
to tell if the backend supports # of queues user requested, which is
done in the following patch.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Tested-by: Marcel Apfelbaum <marcel@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index b7d29b7cf4..f663e5a505 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -122,6 +122,11 @@ void vhost_net_ack_features(struct vhost_net *net, uint64_t features)
     vhost_ack_features(&net->dev, vhost_net_get_feature_bits(net), features);
 }
 
+uint64_t vhost_net_get_max_queues(VHostNetState *net)
+{
+    return net->dev.max_queues;
+}
+
 static int vhost_net_get_fd(NetClientState *backend)
 {
     switch (backend->info->type) {
@@ -144,6 +149,8 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
         goto fail;
     }
 
+    net->dev.max_queues = 1;
+
     if (backend_kernel) {
         r = vhost_net_get_fd(options->net_backend);
         if (r < 0) {
@@ -414,6 +421,11 @@ VHostNetState *get_vhost_net(NetClientState *nc)
     return vhost_net;
 }
 #else
+uint64_t vhost_net_get_max_queues(VHostNetState *net)
+{
+    return 1;
+}
+
 struct vhost_net *vhost_net_init(VhostNetOptions *options)
 {
     error_report("vhost-net support is not compiled in");