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>

2 files changed, 26 insertions, 1 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");
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index 9cb2f52eb7..694fde5bf6 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -25,7 +25,9 @@
 
 #define VHOST_MEMORY_MAX_NREGIONS    8
 #define VHOST_USER_F_PROTOCOL_FEATURES 30
-#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x0ULL
+#define VHOST_USER_PROTOCOL_FEATURE_MASK 0x1ULL
+
+#define VHOST_USER_PROTOCOL_F_MQ    0
 
 typedef enum VhostUserRequest {
     VHOST_USER_NONE = 0,
@@ -45,6 +47,7 @@ typedef enum VhostUserRequest {
     VHOST_USER_SET_VRING_ERR = 14,
     VHOST_USER_GET_PROTOCOL_FEATURES = 15,
     VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+    VHOST_USER_GET_QUEUE_NUM = 17,
     VHOST_USER_MAX
 } VhostUserRequest;
 
@@ -211,6 +214,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
     switch (msg_request) {
     case VHOST_USER_GET_FEATURES:
     case VHOST_USER_GET_PROTOCOL_FEATURES:
+    case VHOST_USER_GET_QUEUE_NUM:
         need_reply = 1;
         break;
 
@@ -315,6 +319,7 @@ static int vhost_user_call(struct vhost_dev *dev, unsigned long int request,
         switch (msg_request) {
         case VHOST_USER_GET_FEATURES:
         case VHOST_USER_GET_PROTOCOL_FEATURES:
+        case VHOST_USER_GET_QUEUE_NUM:
             if (msg.size != sizeof(m.u64)) {
                 error_report("Received bad msg size.");
                 return -1;
@@ -366,6 +371,14 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque)
         if (err < 0) {
             return err;
         }
+
+        /* query the max queues we support if backend supports Multiple Queue */
+        if (dev->protocol_features & (1ULL << VHOST_USER_PROTOCOL_F_MQ)) {
+            err = vhost_user_call(dev, VHOST_USER_GET_QUEUE_NUM, &dev->max_queues);
+            if (err < 0) {
+                return err;
+            }
+        }
     }
 
     return 0;