vhost-user-rng: backend: Add RNG vhost-user daemon implementation

This patch provides the vhost-user backend implementation to work
in tandem with the vhost-user-rng implementation of the QEMU VMM.

It uses the vhost-user API so that other VMM can re-use the interface
without having to write the driver again.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Message-Id: <20210710005929.1702431-4-mathieu.poirier@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/meson.build

@@ -24,3 +24,11 @@ endif
 if have_virtiofsd
   subdir('virtiofsd')
 endif
+
+have_virtiorng = (have_system and
+    have_tools and
+    'CONFIG_LINUX' in config_host)
+
+if have_virtiorng
+  subdir('vhost-user-rng')
+endif

tools/vhost-user-rng/50-qemu-rng.json.in

@@ -0,0 +1,5 @@
+{
+  "description": "QEMU vhost-user-rng",
+  "type": "bridge",
+  "binary": "@libexecdir@/vhost-user-rng"
+}