RE: [PATCH] ui/gtk: flush display pipeline before saving vmstate when blob=true

[Kim, Dongwon]

Hi Marc-André,

> -----Original Message-----
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> Sent: Monday, December 4, 2023 11:15 PM
> To: Kim, Dongwon <dongwon.kim@intel.com>
> Cc: qemu-devel@nongnu.org; Kasireddy, Vivek <vivek.kasireddy@intel.com>
> Subject: Re: [PATCH] ui/gtk: flush display pipeline before saving vmstate when
> blob=true
> 
> Hi
> 
> On Tue, Dec 5, 2023 at 6:40 AM Dongwon Kim <dongwon.kim@intel.com>
> wrote:
> >
> > If the guest state is paused before it gets a response for the current
> > scanout frame submission (resource-flush), it won't start submitting
> > new frames after being restored as it still waits for the old
> > response, which is accepted as a scanout render done signal. So it's
> > needed to unblock the current scanout render pipeline before the run
> > state is changed to make sure the guest receives the response for the
> > current frame submission.
> >
> > Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> > Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
> > Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
> > ---
> >  ui/gtk.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/ui/gtk.c b/ui/gtk.c
> > index 810d7fc796..0f6237dd2f 100644
> > --- a/ui/gtk.c
> > +++ b/ui/gtk.c
> > @@ -678,6 +678,18 @@ static const DisplayGLCtxOps egl_ctx_ops = {
> > static void gd_change_runstate(void *opaque, bool running, RunState
> > state)  {
> >      GtkDisplayState *s = opaque;
> > +    int i;
> > +
> > +    if (state == RUN_STATE_SAVE_VM) {
> > +        for (i = 0; i < s->nb_vcs; i++) {
> > +            VirtualConsole *vc = &s->vc[i];
> > +
> > +            if (vc->gfx.guest_fb.dmabuf) {
> 
> && ..dmabuf->fence_fd >= 0
> 
> > +                /* force flushing current scanout blob rendering process */
> > +                gd_hw_gl_flushed(vc);
> 
> This defeats the purpose of the fence, maybe we should wait for it to be
> signaled first. At worse, I suppose the client can have some glitches. 
> Although
> since the guest is stopped, this is unlikely.
[Kim, Dongwon] 
So this is the flow you are referring to?

            if (vc->gfx.guest_fb.dmabuf &&
                vc->gfx.guest_fb.dmabuf->fence_fd >= 0) {
                EGLint ret = eglClientWaitSync(qemu_egl_display,
                                               vc->gfx.guest_fb.dmabuf->sync,
                                               EGL_SYNC_FLUSH_COMMANDS_BIT_KHR,
                                               100000000); /* timeout of 100ms 
*/

                if (ret != EGL_CONDITION_SATISFIED_KHR) {
                    /* force flushing current scanout blob rendering process */
                    gd_hw_gl_flushed(vc);
                }
            }

If yes, I will test this then create v2 based on this flow.
Thanks