vhost-net-user: add stubs for when no virtio-net device is present

hw/net/vhost_net.c needs functions that are declared in net/vhost-user.c: the
vhost-user code is always compiled into QEMU, only the constructor
net_init_vhost_user is unreachable.  Also, net/vhost-user.c needs functions
declared in hw/virtio/vhost-stub.c even if no virtio device exists.

Break this dependency.  First, add a minimal version of net/vhost-user.c,
with no functionality and no dependency on vhost code.  Second, #ifdef out
the calls back to net/vhost-user.c from hw/net/vhost_net.c.

While at it, this patch fixes the CONFIG_VHOST_NET_USE*D* typo.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <1543851204-41186-3-git-send-email-pbonzini@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1550165756-21617-3-git-send-email-pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

configure

@@ -6590,7 +6590,7 @@ if test "$vhost_scsi" = "yes" ; then
   echo "CONFIG_VHOST_SCSI=y" >> $config_host_mak
 fi
 if test "$vhost_net" = "yes" && test "$vhost_user" = "yes"; then
-  echo "CONFIG_VHOST_NET_USED=y" >> $config_host_mak
+  echo "CONFIG_VHOST_NET_USER=y" >> $config_host_mak
 fi
 if test "$vhost_crypto" = "yes" ; then
   echo "CONFIG_VHOST_CRYPTO=y" >> $config_host_mak

hw/net/vhost_net.c

@@ -193,6 +193,7 @@ 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 (~net->dev.features & features) {
@@ -202,6 +203,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
             goto fail;
         }
     }
+#endif
 
     vhost_net_ack_features(net, features);
 
@@ -413,10 +415,12 @@ VHostNetState *get_vhost_net(NetClientState *nc)
     case NET_CLIENT_DRIVER_TAP:
         vhost_net = tap_get_vhost_net(nc);
         break;
+#ifdef CONFIG_VHOST_NET_USER
     case NET_CLIENT_DRIVER_VHOST_USER:
         vhost_net = vhost_user_get_vhost_net(nc);
         assert(vhost_net);
         break;
+#endif
     default:
         break;
     }

net/Makefile.objs

@@ -3,7 +3,9 @@ common-obj-y += socket.o
 common-obj-y += dump.o
 common-obj-y += eth.o
 common-obj-$(CONFIG_L2TPV3) += l2tpv3.o
-common-obj-$(CONFIG_POSIX) += vhost-user.o
+common-obj-$(call land,$(CONFIG_VIRTIO_NET),$(CONFIG_VHOST_NET_USER)) += vhost-user.o
+common-obj-$(call land,$(call lnot,$(CONFIG_VIRTIO_NET)),$(CONFIG_VHOST_NET_USER)) += vhost-user-stub.o
+common-obj-$(CONFIG_ALL) += vhost-user-stub.o
 common-obj-$(CONFIG_SLIRP) += slirp.o
 common-obj-$(CONFIG_VDE) += vde.o
 common-obj-$(CONFIG_NETMAP) += netmap.o

net/net.c

@@ -961,7 +961,7 @@ static int (* const net_client_init_fun[NET_CLIENT_DRIVER__MAX])(
         [NET_CLIENT_DRIVER_BRIDGE]    = net_init_bridge,
 #endif
         [NET_CLIENT_DRIVER_HUBPORT]   = net_init_hubport,
-#ifdef CONFIG_VHOST_NET_USED
+#ifdef CONFIG_VHOST_NET_USER
         [NET_CLIENT_DRIVER_VHOST_USER] = net_init_vhost_user,
 #endif
 #ifdef CONFIG_L2TPV3

net/vhost-user-stub.c

@@ -0,0 +1,23 @@
+/*
+ * vhost-user-stub.c
+ *
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "clients.h"
+#include "net/vhost_net.h"
+#include "net/vhost-user.h"
+#include "qemu/error-report.h"
+#include "qapi/error.h"
+
+int net_init_vhost_user(const Netdev *netdev, const char *name,
+                        NetClientState *peer, Error **errp)
+{
+    error_setg(errp, "vhost-user requires frontend driver virtio-net-*");
+    return -1;
+}