spice: Disallow use of gl + TCP port

Currently, virgl support has to go through a local unix socket, trying
to connect to a VM using -spice gl through spice://localhost:5900 will
only result in a black screen.
This commit errors out when the user tries to start a VM with both GL
support and a port/tls-port set.
This would fit better in spice-server, but currently QEMU does not call
into spice-server when parsing 'gl' on its command line, so we have to
do this check in QEMU instead.
Signed-off-by: NChristophe Fergeau <cfergeau@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 1457955672-28758-1-git-send-email-cfergeau@redhat.com

[ applied codestyle fix: break long line ]
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

ui/spice-core.c

@@ -828,6 +828,11 @@ void qemu_spice_init(void)
 
 #ifdef HAVE_SPICE_GL
     if (qemu_opt_get_bool(opts, "gl", 0)) {
+        if ((port != 0) || (tls_port != 0)) {
+            error_report("SPICE GL support is local-only for now and "
+                         "incompatible with -spice port/tls-port");
+            exit(1);
+        }
         if (egl_rendernode_init() == 0) {
             display_opengl = 1;
         }