Re: [PATCH 1/3] ui/gtk: skip drawing guest scanout when associated VC is invisible

[Daniel P . Berrangé]

On Tue, Jan 30, 2024 at 03:48:38PM -0800, dongwon.kim@intel.com wrote:
> From: Dongwon Kim <dongwon.kim@intel.com>
> 
> A new flag "visible" is added to show visibility status of the gfx console.
> The flag is set to 'true' when the VC is visible but set to 'false' when
> it is hidden or closed. When the VC is invisible, drawing guest frames
> should be skipped as it will never be completed and it would potentially
> lock up the guest display especially when blob scanout is used.
> 
> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
> 
> Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
> ---
>  include/ui/gtk.h |  1 +
>  ui/gtk-egl.c     |  8 ++++++++
>  ui/gtk-gl-area.c |  8 ++++++++
>  ui/gtk.c         | 10 +++++++++-
>  4 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/include/ui/gtk.h b/include/ui/gtk.h
> index aa3d637029..2de38e5724 100644
> --- a/include/ui/gtk.h
> +++ b/include/ui/gtk.h
> @@ -57,6 +57,7 @@ typedef struct VirtualGfxConsole {
>      bool y0_top;
>      bool scanout_mode;
>      bool has_dmabuf;
> +    bool visible;
>  #endif
>  } VirtualGfxConsole;
>  
> diff --git a/ui/gtk-egl.c b/ui/gtk-egl.c
> index 3af5ac5bcf..993c283191 100644
> --- a/ui/gtk-egl.c
> +++ b/ui/gtk-egl.c
> @@ -265,6 +265,10 @@ void gd_egl_scanout_dmabuf(DisplayChangeListener *dcl,
>  #ifdef CONFIG_GBM
>      VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl);
>  
> +    if (!vc->gfx.visible) {
> +        return;
> +    }
> +
>      eglMakeCurrent(qemu_egl_display, vc->gfx.esurface,
>                     vc->gfx.esurface, vc->gfx.ectx);
>  
> @@ -363,6 +367,10 @@ void gd_egl_flush(DisplayChangeListener *dcl,
>      VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl);
>      GtkWidget *area = vc->gfx.drawing_area;
>  
> +    if (!vc->gfx.visible) {
> +        return;
> +    }
> +
>      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;
> diff --git a/ui/gtk-gl-area.c b/ui/gtk-gl-area.c
> index 52dcac161e..04e07bd7ee 100644
> --- a/ui/gtk-gl-area.c
> +++ b/ui/gtk-gl-area.c
> @@ -285,6 +285,10 @@ void gd_gl_area_scanout_flush(DisplayChangeListener *dcl,
>  {
>      VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl);
>  
> +    if (!vc->gfx.visible) {
> +        return;
> +    }
> +
>      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;
> @@ -299,6 +303,10 @@ void gd_gl_area_scanout_dmabuf(DisplayChangeListener 
> *dcl,
>  #ifdef CONFIG_GBM
>      VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl);
>  
> +    if (!vc->gfx.visible) {
> +        return;
> +    }
> +
>      gtk_gl_area_make_current(GTK_GL_AREA(vc->gfx.drawing_area));
>      egl_dmabuf_import_texture(dmabuf);
>      if (!dmabuf->texture) {

If we skip processing these requests, what happens when the
QEMU windows is then re-displayed. Won't it now be missing
updates to various regions of the guest display ?

>
With regards,
Daniel
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