opengl: add egl-headless display

Add egl-headless user interface.  It doesn't provide a real user
interface, it only provides opengl support using drm render nodes.
It will copy back the bits rendered by the guest using virgl back
to a DisplaySurface and kick the usual display update code paths,
so spice and vnc and screendump can pick it up.

Use it this way:
  qemu -display egl-headless -vnc $display
  qemu -display egl-headless -spice gl=off,$args

Note that you should prefer native spice opengl support (-spice
gl=on) if possible because that delivers better performance.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20170505104101.30589-7-kraxel@redhat.com

1 files changed, 16 insertions, 0 deletions

diff --git a/vl.c b/vl.c
index 58023fca02..aca99e1c77 100644
--- a/vl.c
+++ b/vl.c
@@ -2050,6 +2050,7 @@ typedef enum DisplayType {
     DT_SDL,
     DT_COCOA,
     DT_GTK,
+    DT_EGL,
     DT_NONE,
 } DisplayType;
 
@@ -2127,6 +2128,15 @@ static DisplayType select_display(const char *p)
             error_report("VNC requires a display argument vnc=<display>");
             exit(1);
         }
+    } else if (strstart(p, "egl-headless", &opts)) {
+#ifdef CONFIG_OPENGL
+        request_opengl = 1;
+        display_opengl = 1;
+        display = DT_EGL;
+#else
+        fprintf(stderr, "egl support is disabled\n");
+        exit(1);
+#endif
     } else if (strstart(p, "curses", &opts)) {
 #ifdef CONFIG_CURSES
         display = DT_CURSES;
@@ -4659,6 +4669,12 @@ int main(int argc, char **argv, char **envp)
         qemu_spice_display_init();
     }
 
+#ifdef CONFIG_OPENGL
+    if (display_type == DT_EGL) {
+        egl_headless_init();
+    }
+#endif
+
     if (foreach_device_config(DEV_GDB, gdbserver_start) < 0) {
         exit(1);
     }