net: Add get_acked_features callback to VhostNetOptions

This patch continues the effort to decouple the generic vhost layer
from specific network backend implementations.

Previously, the vhost_net initialization code contained a hardcoded
check for the vhost-user client type to retrieve its acked features
by calling vhost_user_get_acked_features(). This exposed an
internal vhost-user function in a public header and coupled the two
modules.

The vhost-user backend is updated to provide a callback, and its
getter function is now static. The call site in vhost_net.c is
simplified to use the new generic helper, removing the type check and
the direct dependency.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/vhost_net.c

@@ -288,9 +288,8 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     }
 
     /* Set sane init value. Override when guest acks. */
-#ifdef CONFIG_VHOST_NET_USER
-    if (net->nc->info->type == NET_CLIENT_DRIVER_VHOST_USER) {
-        features = vhost_user_get_acked_features(net->nc);
+    if (options->get_acked_features) {
+        features = options->get_acked_features(net->nc);
         if (~net->dev.features & features) {
             fprintf(stderr, "vhost lacks feature mask 0x%" PRIx64
                     " for backend\n",
@@ -298,7 +297,6 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
             goto fail;
         }
     }
-#endif
 
     vhost_net_ack_features(net, features);
 

include/net/vhost-user.h

@@ -11,8 +11,6 @@
 #ifndef VHOST_USER_H
 #define VHOST_USER_H
 
-struct vhost_net;
-uint64_t vhost_user_get_acked_features(NetClientState *nc);
 void vhost_user_save_acked_features(NetClientState *nc);
 
 #endif /* VHOST_USER_H */

include/net/vhost_net.h

@@ -7,12 +7,15 @@
 struct vhost_net;
 typedef struct vhost_net VHostNetState;
 
+typedef uint64_t (GetAckedFeatures)(NetClientState *nc);
+
 typedef struct VhostNetOptions {
     VhostBackendType backend_type;
     NetClientState *net_backend;
     uint32_t busyloop_timeout;
     unsigned int nvqs;
     const int *feature_bits;
+    GetAckedFeatures *get_acked_features;
     void *opaque;
 } VhostNetOptions;
 

net/tap.c

@@ -744,6 +744,7 @@ static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
         options.opaque = (void *)(uintptr_t)vhostfd;
         options.nvqs = 2;
         options.feature_bits = kernel_feature_bits;
+        options.get_acked_features = NULL;
 
         s->vhost_net = vhost_net_init(&options);
         if (!s->vhost_net) {

net/vhost-user.c

@@ -81,7 +81,7 @@ static struct vhost_net *vhost_user_get_vhost_net(NetClientState *nc)
     return s->vhost_net;
 }
 
-uint64_t vhost_user_get_acked_features(NetClientState *nc)
+static uint64_t vhost_user_get_acked_features(NetClientState *nc)
 {
     NetVhostUserState *s = DO_UPCAST(NetVhostUserState, nc, nc);
     assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_USER);
@@ -139,6 +139,8 @@ static int vhost_user_start(int queues, NetClientState *ncs[],
         options.busyloop_timeout = 0;
         options.nvqs = 2;
         options.feature_bits = user_feature_bits;
+        options.get_acked_features = vhost_user_get_acked_features;
+
         net = vhost_net_init(&options);
         if (!net) {
             error_report("failed to init vhost_net for queue %d", i);

net/vhost-vdpa.c

@@ -202,6 +202,7 @@ static int vhost_vdpa_add(NetClientState *ncs, void *be,
     options.busyloop_timeout = 0;
     options.nvqs = nvqs;
     options.feature_bits = vdpa_feature_bits;
+    options.get_acked_features = NULL;
 
     net = vhost_net_init(&options);
     if (!net) {