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

[Kim, Dongwon]

Hi Daniel,

> -----Original Message-----
> From: Daniel P. Berrangé <berrange@redhat.com>
> Sent: Thursday, March 7, 2024 1:41 AM
> To: Kim, Dongwon <dongwon.kim@intel.com>
> Cc: qemu-devel@nongnu.org
> Subject: Re: [PATCH 1/3] ui/gtk: skip drawing guest scanout when associated
> VC is invisible
> 
> 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 ?
 
[Kim, Dongwon]  Scanout blob is continuously submitted by the guest even when 
the vc->visible is false. So it will just display the current guest frame right 
away when the window is redisplayed again.

> 
> >
> With regards,
> Daniel
> --
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