virgl: comment on a sync issue in transfers

Signed-off-by: Chia-I Wu <[email protected]>
Reviewed-by: Alexandros Frantzis <[email protected]>
Reviewed-by: Gurchetan Singh <[email protected]>

2 files changed, 20 insertions, 0 deletions

diff --git a/src/gallium/drivers/virgl/virgl_buffer.c b/src/gallium/drivers/virgl/virgl_buffer.c
index d4bde39096e..f955b7c624b 100644
--- a/src/gallium/drivers/virgl/virgl_buffer.c
+++ b/src/gallium/drivers/virgl/virgl_buffer.c
@@ -53,6 +53,16 @@ static void *virgl_buffer_transfer_map(struct pipe_context *ctx,
       vs->vws->transfer_get(vs->vws, vbuf->hw_res, box, trans->base.stride,
                             trans->l_stride, trans->offset, level);
 
+   /* XXX Consider
+    *
+    *   glBufferSubData(GL_ARRAY_BUFFER, 0, 12, data1);
+    *   glDrawArrays(..);
+    *   glFlush();
+    *   glBufferSubData(GL_ARRAY_BUFFER, 0, 12, data2)
+    *
+    * readback and flush are both false in the second glBufferSubData call.
+    * The draw call might end up seeing data2.
+    */
    if (readback || flush)
       vs->vws->resource_wait(vs->vws, vbuf->hw_res);
 
diff --git a/src/gallium/drivers/virgl/virgl_texture.c b/src/gallium/drivers/virgl/virgl_texture.c
index 19ae6ff1d3a..53cd038e500 100644
--- a/src/gallium/drivers/virgl/virgl_texture.c
+++ b/src/gallium/drivers/virgl/virgl_texture.c
@@ -143,6 +143,16 @@ static void *texture_transfer_map_plain(struct pipe_context *ctx,
       vws->transfer_get(vws, vtex->hw_res, box, trans->base.stride,
                         trans->l_stride, trans->offset, level);
 
+   /* XXX Consider
+    *
+    *   glTexImage2D(..., data1);
+    *   glDrawArrays();
+    *   glFlush();
+    *   glTexImage2D(..., data2);
+    *
+    * readback and flush are both false in the second glTexImage2D call.  The
+    * draw call might end up seeing data2.
+    */
    if (readback || flush)
       vws->resource_wait(vws, vtex->hw_res);