[PATCH v2 3/5] ramfb: implement migration support

[marcandre . lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Implementing RAMFB migration is quite straightforward. One caveat is to
treat the whole RAMFBCfg as a blob, since that's what is exposed to the
guest directly. This avoid having to fiddle with endianness issues if we
were to migrate fields individually as integers.

The following patches turns the migration only on machine >= 8.2.

Fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1859424

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/display/ramfb.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/display/ramfb.c b/hw/display/ramfb.c
index 79b9754a58..4aaaa7d653 100644
--- a/hw/display/ramfb.c
+++ b/hw/display/ramfb.c
@@ -12,6 +12,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "migration/vmstate.h"
 #include "qapi/error.h"
 #include "hw/loader.h"
 #include "hw/display/ramfb.h"
@@ -28,6 +29,8 @@ struct QEMU_PACKED RAMFBCfg {
     uint32_t stride;
 };
 
+typedef struct RAMFBCfg RAMFBCfg;
+
 struct RAMFBState {
     DisplaySurface *ds;
     uint32_t width, height;
@@ -115,6 +118,23 @@ void ramfb_display_update(QemuConsole *con, RAMFBState *s)
     dpy_gfx_update_full(con);
 }
 
+static int ramfb_post_load(void *opaque, int version_id)
+{
+    ramfb_fw_cfg_write(opaque, 0, 0);
+    return 0;
+}
+
+static const VMStateDescription vmstate_ramfb = {
+    .name = "ramfb",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .post_load = ramfb_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_BUFFER_UNSAFE(cfg, RAMFBState, 0, sizeof(RAMFBCfg)),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 RAMFBState *ramfb_setup(Error **errp)
 {
     FWCfgState *fw_cfg = fw_cfg_find();
@@ -127,6 +147,7 @@ RAMFBState *ramfb_setup(Error **errp)
 
     s = g_new0(RAMFBState, 1);
 
+    vmstate_register(NULL, 0, &vmstate_ramfb, s);
     rom_add_vga("vgabios-ramfb.bin");
     fw_cfg_add_file_callback(fw_cfg, "etc/ramfb",
                              NULL, ramfb_fw_cfg_write, s,
-- 
2.41.0