Re: [PATCH 12/16] ui/surface: allocate shared memory on !win32

[Akihiko Odaki]

On 2024/10/03 20:22, marcandre.lur...@redhat.com wrote:
From: Marc-André Lureau <marcandre.lur...@redhat.com>
Use qemu_memfd_alloc() to allocate the display surface memory, which
will fallback on tmpfile/mmap() on systems without memfd, and allow to
share the display with other processes.

This is similar to how display memory is allocated on win32 since commit
09b4c198 ("console/win32: allocate shareable display surface").

Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
---
  include/ui/surface.h |  8 ++++++++
  ui/console.c         | 30 ++++++++++++++++++++++++++++--
  2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/include/ui/surface.h b/include/ui/surface.h
index 345b19169d..dacf12ffe2 100644
--- a/include/ui/surface.h
+++ b/include/ui/surface.h
@@ -23,6 +23,10 @@ typedef struct DisplaySurface {
      GLenum gltype;
      GLuint texture;
  #endif
+#ifndef WIN32
+    int shmfd;
+    uint32_t shmfd_offset;
+#endif
  #ifdef WIN32
      HANDLE handle;

What about defining a new struct that contains either of shmfd or 
handle? We can then have a unified set of functions that uses the struct 
to allocate/free a shared pixman image and to set one to DisplaySurface.

      uint32_t handle_offset;
@@ -37,6 +41,10 @@ DisplaySurface *qemu_create_displaysurface_from(int width, 
int height,
  DisplaySurface *qemu_create_displaysurface_pixman(pixman_image_t *image);
  DisplaySurface *qemu_create_placeholder_surface(int w, int h,
                                                  const char *msg);
+#ifndef WIN32
+void qemu_displaysurface_set_shmfd(DisplaySurface *surface,
+                                   int shmfd, uint32_t offset);
+#endif
  #ifdef WIN32
  void qemu_displaysurface_win32_set_handle(DisplaySurface *surface,
                                            HANDLE h, uint32_t offset);
diff --git a/ui/console.c b/ui/console.c
index fdd76c2be4..56f2462c3d 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -37,6 +37,7 @@
  #include "trace.h"
  #include "exec/memory.h"
  #include "qom/object.h"
+#include "qemu/memfd.h"
  
  #include "console-priv.h"
  
@@ -452,6 +453,17 @@ qemu_graphic_console_init(Object *obj)
  {
  }
  
+#ifndef WIN32
+void qemu_displaysurface_set_shmfd(DisplaySurface *surface,
+                                   int shmfd, uint32_t offset)
+{
+    assert(surface->shmfd == -1);
+
+    surface->shmfd = shmfd;
+    surface->shmfd_offset = offset;
+}
+#endif
+
  #ifdef WIN32
  void qemu_displaysurface_win32_set_handle(DisplaySurface *surface,
                                            HANDLE h, uint32_t offset)
@@ -469,12 +481,16 @@ DisplaySurface *qemu_create_displaysurface(int width, int 
height)
      void *bits = NULL;
  #ifdef WIN32
      HANDLE handle = NULL;
+#else
+    int shmfd = -1;
  #endif
  
      trace_displaysurface_create(width, height);
  
  #ifdef WIN32
      bits = qemu_win32_map_alloc(width * height * 4, &handle, &error_abort);
+#else
+    bits = qemu_memfd_alloc("displaysurface", width * height * 4, 0, &shmfd, 
&error_abort);
  #endif
  
      surface = qemu_create_displaysurface_from(
@@ -486,9 +502,13 @@ DisplaySurface *qemu_create_displaysurface(int width, int 
height)
  
  #ifdef WIN32
      qemu_displaysurface_win32_set_handle(surface, handle, 0);
-    pixman_image_set_destroy_function(surface->image,
-                                      qemu_pixman_shared_image_destroy, 
handle);
+    void *data = handle;
+#else
+    qemu_displaysurface_set_shmfd(surface, shmfd, 0);
+    void *data = GINT_TO_POINTER(shmfd);
  #endif
+    pixman_image_set_destroy_function(surface->image, 
qemu_pixman_shared_image_destroy, data);
+
      return surface;
  }
  
@@ -499,6 +519,9 @@ DisplaySurface *qemu_create_displaysurface_from(int width, int height,
      DisplaySurface *surface = g_new0(DisplaySurface, 1);
  
      trace_displaysurface_create_from(surface, width, height, format);
+#ifndef WIN32
+    surface->shmfd = -1;
+#endif
      surface->image = pixman_image_create_bits(format,
                                                width, height,
                                                (void *)data, linesize);
@@ -512,6 +535,9 @@ DisplaySurface 
*qemu_create_displaysurface_pixman(pixman_image_t *image)
      DisplaySurface *surface = g_new0(DisplaySurface, 1);
  
      trace_displaysurface_create_pixman(surface);
+#ifndef WIN32
+    surface->shmfd = -1;
+#endif
      surface->image = pixman_image_ref(image);
  
      return surface;