ui/gtk: skip any extra draw of same guest scanout blob res

Any extra draw call for the same blob resource representing guest scanout
before the previous drawing is not finished can break synchronous draw
sequence. To prevent this, drawing is now done only once for each draw
submission (when draw_submitted == true).

v2:
 - removed mutex
 - updated commit msg

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Message-Id: <20210924225105.24930-1-dongwon.kim@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/virtio-gpu-udmabuf.c

@@ -186,7 +186,7 @@ static VGPUDMABuf
     dmabuf->buf.fourcc = qemu_pixman_to_drm_format(fb->format);
     dmabuf->buf.fd = res->dmabuf_fd;
     dmabuf->buf.allow_fences = true;
-
+    dmabuf->buf.draw_submitted = false;
     dmabuf->scanout_id = scanout_id;
     QTAILQ_INSERT_HEAD(&g->dmabuf.bufs, dmabuf, next);
 

include/ui/console.h

@@ -171,6 +171,7 @@ typedef struct QemuDmaBuf {
     void      *sync;
     int       fence_fd;
     bool      allow_fences;
+    bool      draw_submitted;
 } QemuDmaBuf;
 
 typedef struct DisplayState DisplayState;

ui/gtk-egl.c

@@ -63,6 +63,9 @@ void gd_egl_init(VirtualConsole *vc)
 void gd_egl_draw(VirtualConsole *vc)
 {
     GdkWindow *window;
+#ifdef CONFIG_GBM
+    QemuDmaBuf *dmabuf = vc->gfx.guest_fb.dmabuf;
+#endif
     int ww, wh;
 
     if (!vc->gfx.gls) {
@@ -74,10 +77,31 @@ void gd_egl_draw(VirtualConsole *vc)
     wh = gdk_window_get_height(window);
 
     if (vc->gfx.scanout_mode) {
+#ifdef CONFIG_GBM
+        if (dmabuf) {
+            if (!dmabuf->draw_submitted) {
+                return;
+            } else {
+                dmabuf->draw_submitted = false;
+            }
+        }
+#endif
         gd_egl_scanout_flush(&vc->gfx.dcl, 0, 0, vc->gfx.w, vc->gfx.h);
 
         vc->gfx.scale_x = (double)ww / vc->gfx.w;
         vc->gfx.scale_y = (double)wh / vc->gfx.h;
+
+        glFlush();
+#ifdef CONFIG_GBM
+        if (dmabuf) {
+            egl_dmabuf_create_fence(dmabuf);
+            if (dmabuf->fence_fd > 0) {
+                qemu_set_fd_handler(dmabuf->fence_fd, gd_hw_gl_flushed, NULL, vc);
+                return;
+            }
+            graphic_hw_gl_block(vc->gfx.dcl.con, false);
+        }
+#endif
     } else {
         if (!vc->gfx.ds) {
             return;
@@ -92,21 +116,10 @@ void gd_egl_draw(VirtualConsole *vc)
 
         vc->gfx.scale_x = (double)ww / surface_width(vc->gfx.ds);
         vc->gfx.scale_y = (double)wh / surface_height(vc->gfx.ds);
-    }
-
-    glFlush();
-#ifdef CONFIG_GBM
-    if (vc->gfx.guest_fb.dmabuf) {
-        QemuDmaBuf *dmabuf = vc->gfx.guest_fb.dmabuf;
 
-        egl_dmabuf_create_fence(dmabuf);
-        if (dmabuf->fence_fd > 0) {
-            qemu_set_fd_handler(dmabuf->fence_fd, gd_hw_gl_flushed, NULL, vc);
-            return;
-        }
-        graphic_hw_gl_block(vc->gfx.dcl.con, false);
+        glFlush();
     }
-#endif
+
     graphic_hw_gl_flushed(vc->gfx.dcl.con);
 }
 
@@ -317,6 +330,7 @@ void gd_egl_flush(DisplayChangeListener *dcl,
 
     if (vc->gfx.guest_fb.dmabuf) {
         graphic_hw_gl_block(vc->gfx.dcl.con, true);
+        vc->gfx.guest_fb.dmabuf->draw_submitted = true;
         gtk_widget_queue_draw_area(area, x, y, w, h);
         return;
     }

ui/gtk-gl-area.c

@@ -38,6 +38,9 @@ static void gtk_gl_area_set_scanout_mode(VirtualConsole *vc, bool scanout)
 
 void gd_gl_area_draw(VirtualConsole *vc)
 {
+#ifdef CONFIG_GBM
+    QemuDmaBuf *dmabuf = vc->gfx.guest_fb.dmabuf;
+#endif
     int ww, wh, y1, y2;
 
     if (!vc->gfx.gls) {
@@ -53,6 +56,16 @@ void gd_gl_area_draw(VirtualConsole *vc)
             return;
         }
 
+#ifdef CONFIG_GBM
+        if (dmabuf) {
+            if (!dmabuf->draw_submitted) {
+                return;
+            } else {
+                dmabuf->draw_submitted = false;
+            }
+        }
+#endif
+
         glBindFramebuffer(GL_READ_FRAMEBUFFER, vc->gfx.guest_fb.framebuffer);
         /* GtkGLArea sets GL_DRAW_FRAMEBUFFER for us */
 
@@ -62,6 +75,22 @@ void gd_gl_area_draw(VirtualConsole *vc)
         glBlitFramebuffer(0, y1, vc->gfx.w, y2,
                           0, 0, ww, wh,
                           GL_COLOR_BUFFER_BIT, GL_NEAREST);
+#ifdef CONFIG_GBM
+        if (dmabuf) {
+            egl_dmabuf_create_sync(dmabuf);
+        }
+#endif
+        glFlush();
+#ifdef CONFIG_GBM
+        if (dmabuf) {
+            egl_dmabuf_create_fence(dmabuf);
+            if (dmabuf->fence_fd > 0) {
+                qemu_set_fd_handler(dmabuf->fence_fd, gd_hw_gl_flushed, NULL, vc);
+                return;
+            }
+            graphic_hw_gl_block(vc->gfx.dcl.con, false);
+        }
+#endif
     } else {
         if (!vc->gfx.ds) {
             return;
@@ -72,25 +101,6 @@ void gd_gl_area_draw(VirtualConsole *vc)
         surface_gl_render_texture(vc->gfx.gls, vc->gfx.ds);
     }
 
-#ifdef CONFIG_GBM
-    if (vc->gfx.guest_fb.dmabuf) {
-        egl_dmabuf_create_sync(vc->gfx.guest_fb.dmabuf);
-    }
-#endif
-
-    glFlush();
-#ifdef CONFIG_GBM
-    if (vc->gfx.guest_fb.dmabuf) {
-        QemuDmaBuf *dmabuf = vc->gfx.guest_fb.dmabuf;
-
-        egl_dmabuf_create_fence(dmabuf);
-        if (dmabuf->fence_fd > 0) {
-            qemu_set_fd_handler(dmabuf->fence_fd, gd_hw_gl_flushed, NULL, vc);
-            return;
-        }
-        graphic_hw_gl_block(vc->gfx.dcl.con, false);
-    }
-#endif
     graphic_hw_gl_flushed(vc->gfx.dcl.con);
 }
 
@@ -237,6 +247,7 @@ void gd_gl_area_scanout_flush(DisplayChangeListener *dcl,
 
     if (vc->gfx.guest_fb.dmabuf) {
         graphic_hw_gl_block(vc->gfx.dcl.con, true);
+        vc->gfx.guest_fb.dmabuf->draw_submitted = true;
     }
     gtk_gl_area_queue_render(GTK_GL_AREA(vc->gfx.drawing_area));
 }