Re: [PULL 06/19] ui/gtk: set scanout-mode right before scheduling draw

[Volker Rümelin]

Am 17.07.23 um 14:45 schrieb marcandre.lureau@redhat.com:
> From: Dongwon Kim<dongwon.kim@intel.com>
>
> Setting scanout mode is better to be done very last minute
> right because the mode can be reset anytime after it is set in
> dpy_gl_scanout_texture by any asynchronouse dpy_refresh call,
> which eventually cancels drawing of the guest scanout texture.

Hi Dongwon,

this patch breaks the QEMU guest display on my system. QEMU was started 
with ./qemu-system-x86_64 -machine q35 -device 
virtio-vga-gl,xres=1280,yres=768 -display gtk,zoom-to-fit=off,gl=on. I 
can see the OVMF boot screen and then GRUB. After Linux was started, 
plymouth normally shows the OVMF boot logo and a rotating spinner. With 
your patch the guest screen stays black and I see a text cursor in the 
upper left corner. It seems the guest works without issues. I can use 
ssh to log in and I can't find any obvious errors in the guest log 
files. I tested on a host GNOME desktop under X11 and again under 
Wayland. In both cases the result is a black guest screen.

With best regards,
Volker

> Cc: Gerd Hoffmann<kraxel@redhat.com>
> Cc: Marc-André Lureau<marcandre.lureau@redhat.com>
> Cc: Vivek Kasireddy<vivek.kasireddy@intel.com>
> Signed-off-by: Dongwon Kim<dongwon.kim@intel.com>
> Acked-by: Marc-André Lureau<marcandre.lureau@redhat.com>
> Message-ID:<20230706183355.29361-1-dongwon.kim@intel.com>
> ---
>   ui/gtk-egl.c     | 2 +-
>   ui/gtk-gl-area.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/ui/gtk-egl.c b/ui/gtk-egl.c
> index eee821d73a..98b3a116bf 100644
> --- a/ui/gtk-egl.c
> +++ b/ui/gtk-egl.c
> @@ -242,7 +242,6 @@ void gd_egl_scanout_texture(DisplayChangeListener *dcl,
>       eglMakeCurrent(qemu_egl_display, vc->gfx.esurface,
>                      vc->gfx.esurface, vc->gfx.ectx);
>   
> -    gtk_egl_set_scanout_mode(vc, true);
>       egl_fb_setup_for_tex(&vc->gfx.guest_fb, backing_width, backing_height,
>                            backing_id, false);
>   }
> @@ -353,6 +352,7 @@ void gd_egl_flush(DisplayChangeListener *dcl,
>       if (vc->gfx.guest_fb.dmabuf && !vc->gfx.guest_fb.dmabuf->draw_submitted) {
>           graphic_hw_gl_block(vc->gfx.dcl.con, true);
>           vc->gfx.guest_fb.dmabuf->draw_submitted = true;
> +        gtk_egl_set_scanout_mode(vc, true);
>           gtk_widget_queue_draw_area(area, x, y, w, h);
>           return;
>       }
> diff --git a/ui/gtk-gl-area.c b/ui/gtk-gl-area.c
> index 4513d3d059..28d9e49888 100644
> --- a/ui/gtk-gl-area.c
> +++ b/ui/gtk-gl-area.c
> @@ -264,7 +264,6 @@ void gd_gl_area_scanout_texture(DisplayChangeListener *dcl,
>           return;
>       }
>   
> -    gtk_gl_area_set_scanout_mode(vc, true);
>       egl_fb_setup_for_tex(&vc->gfx.guest_fb, backing_width, backing_height,
>                            backing_id, false);
>   }
> @@ -284,6 +283,7 @@ void gd_gl_area_scanout_flush(DisplayChangeListener *dcl,
>       if (vc->gfx.guest_fb.dmabuf && !vc->gfx.guest_fb.dmabuf->draw_submitted) {
>           graphic_hw_gl_block(vc->gfx.dcl.con, true);
>           vc->gfx.guest_fb.dmabuf->draw_submitted = true;
> +        gtk_gl_area_set_scanout_mode(vc, true);
>       }
>       gtk_gl_area_queue_render(GTK_GL_AREA(vc->gfx.drawing_area));
>   }