[RFC PATCH v2 01/20] migration/vmstate: Restrict vmstate_dummy to user-mode

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

'vmstate_dummy' is special and only used for user-mode. Rename
it to something more specific.
It was introduced restricted to user-mode in commit c71c3e99b8
("Add a vmstate_dummy struct for CONFIG_USER_ONLY") but this
restriction was later removed in commit 6afc14e92ac ("migration:
Fix warning caused by missing declaration of vmstate_dummy").
Avoid the missing declaration warning by adding a stub for the
symbol, and restore the #ifdef'ry.

Suggested-by: Daniel Berrangé <berrange@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 include/hw/core/cpu.h       | 2 +-
 include/migration/vmstate.h | 4 +++-
 stubs/vmstate.c             | 4 +++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 140fa32a5e3..c79a58db9b9 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -1132,7 +1132,7 @@ bool target_words_bigendian(void);
 #ifdef CONFIG_SOFTMMU
 extern const VMStateDescription vmstate_cpu_common;
 #else
-#define vmstate_cpu_common vmstate_dummy
+#define vmstate_cpu_common vmstate_user_mode_cpu_dummy
 #endif
 
 #define VMSTATE_CPU() {                                                     \
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 075ee800960..dda65c9987d 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -194,7 +194,9 @@ struct VMStateDescription {
     const VMStateDescription **subsections;
 };
 
-extern const VMStateDescription vmstate_dummy;
+#if defined(CONFIG_USER_ONLY)
+extern const VMStateDescription vmstate_user_mode_cpu_dummy;
+#endif
 
 extern const VMStateInfo vmstate_info_bool;
 
diff --git a/stubs/vmstate.c b/stubs/vmstate.c
index cc4fe41dfc2..8da777a1fb4 100644
--- a/stubs/vmstate.c
+++ b/stubs/vmstate.c
@@ -1,7 +1,9 @@
 #include "qemu/osdep.h"
 #include "migration/vmstate.h"
 
-const VMStateDescription vmstate_dummy = {};
+#if defined(CONFIG_USER_ONLY)
+const VMStateDescription vmstate_user_mode_cpu_dummy = {};
+#endif
 
 int vmstate_register_with_alias_id(VMStateIf *obj,
                                    uint32_t instance_id,
-- 
2.26.2