SDL API changes GL context to a newly created GL context, which differs
from other GL providers that don't switch context. Change SDL backend to
restore the original GL context. This allows Qemu's virtio-gpu to support
new virglrenderer async-fencing feature for Virgl contexts, otherwise
virglrenderer's vrend creates a fence-sync context on the Qemu's
main-loop thread that erroneously stays in-use by the main-loop after
creation, not allowing vrend's fence-sync thread switch to this new
context that belongs to it.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 ui/sdl2-gl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/ui/sdl2-gl.c b/ui/sdl2-gl.c
index e01d9ab0c7bf..b1fe96d6af22 100644
--- a/ui/sdl2-gl.c
+++ b/ui/sdl2-gl.c
@@ -168,6 +168,9 @@ QEMUGLContext sdl2_gl_create_context(DisplayGLCtx *dgc,
                             SDL_GL_CONTEXT_PROFILE_ES);
         ctx = SDL_GL_CreateContext(scon->real_window);
     }
+
+    SDL_GL_MakeCurrent(scon->real_window, scon->winctx);
+
     return (QEMUGLContext)ctx;
 }
 
-- 
2.47.0