vfio/display: Fix vfio_display_edid_init() error path

vfio_display_edid_init() can fail for many reasons and return silently.
It would be good to report the error.

Old mdev driver may not support vfio edid region and we allow to go
through in this case.

vfio_display_edid_update() isn't changed because it can be called at
runtime when UI changes (i.e. window resize).

Fixes: 08479114b0de ("vfio/display: add edid support.")
Suggested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

hw/vfio/display.c

@@ -124,7 +124,7 @@ static void vfio_display_edid_ui_info(void *opaque, uint32_t idx,
     }
 }
 
-static void vfio_display_edid_init(VFIOPCIDevice *vdev)
+static bool vfio_display_edid_init(VFIOPCIDevice *vdev, Error **errp)
 {
     VFIODisplay *dpy = vdev->dpy;
     int fd = vdev->vbasedev.fd;
@@ -135,7 +135,8 @@ static void vfio_display_edid_init(VFIOPCIDevice *vdev)
                                    VFIO_REGION_SUBTYPE_GFX_EDID,
                                    &dpy->edid_info);
     if (ret) {
-        return;
+        /* Failed to get GFX edid info, allow to go through without edid. */
+        return true;
     }
 
     trace_vfio_display_edid_available();
@@ -167,15 +168,16 @@ static void vfio_display_edid_init(VFIOPCIDevice *vdev)
                                         vfio_display_edid_link_up, vdev);
 
     vfio_display_edid_update(vdev, true, 0, 0);
-    return;
+    return true;
 
 err:
+    error_setg(errp, "vfio: failed to read GFX edid field");
     trace_vfio_display_edid_write_error();
     g_free(dpy->edid_info);
     g_free(dpy->edid_regs);
     dpy->edid_info = NULL;
     dpy->edid_regs = NULL;
-    return;
+    return false;
 }
 
 static void vfio_display_edid_exit(VFIODisplay *dpy)
@@ -368,8 +370,7 @@ static bool vfio_display_dmabuf_init(VFIOPCIDevice *vdev, Error **errp)
             return false;
         }
     }
-    vfio_display_edid_init(vdev);
-    return true;
+    return vfio_display_edid_init(vdev, errp);
 }
 
 static void vfio_display_dmabuf_exit(VFIODisplay *dpy)