configure: Fix build dependencies with vhost-vdpa.

Following the same logic as for vhost-net-user and vhost-kernel,
enable vhost-net if vhost-net-vdpa is enabled and vhost-net is not
explicitly disabled.
See 299e6f19b3 ("vhost-net: revamp configure logic")

Autoselect VHOST if VHOST_VDPA is set
See 21c6b0c87e ("configure: simplify vhost condition with Kconfig")
See 2becc36a3e ("meson: infrastructure for building emulators"

Problems can be triggered using;
... --enable-vhost-vdpa --disable-vhost-user --disable-vhost-kernel ...

Fixes: 108a64818e ("vhost-vdpa: introduce vhost-vdpa backend")
Cc: lulu@redhat.com
Cc: pbonzini@redhat.com
Cc: marcandre.lureau@redhat.com
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20200924210023.160679-1-lvivier@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Kconfig.host

@@ -24,6 +24,10 @@ config VHOST_USER
     bool
     select VHOST
 
+config VHOST_VDPA
+    bool
+    select VHOST
+
 config VHOST_KERNEL
     bool
     select VHOST

configure

@@ -2494,9 +2494,10 @@ if test "$vhost_net_vdpa" = "yes" && test "$vhost_vdpa" = "no"; then
   error_exit "--enable-vhost-net-vdpa requires --enable-vhost-vdpa"
 fi
 
-# OR the vhost-kernel and vhost-user values for simplicity
+# OR the vhost-kernel, vhost-vdpa and vhost-user values for simplicity
 if test "$vhost_net" = ""; then
   test "$vhost_net_user" = "yes" && vhost_net=yes
+  test "$vhost_net_vdpa" = "yes" && vhost_net=yes
   test "$vhost_kernel" = "yes" && vhost_net=yes
 fi
 

meson.build

@@ -521,6 +521,7 @@ kconfig_external_symbols = [
   'CONFIG_OPENGL',
   'CONFIG_X11',
   'CONFIG_VHOST_USER',
+  'CONFIG_VHOST_VDPA',
   'CONFIG_VHOST_KERNEL',
   'CONFIG_VIRTFS',
   'CONFIG_LINUX',