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

[Peter Maydell <peter.maydell@linaro.org>]

On Sun, 17 Jan 2021 at 19:24, Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>
> '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.

So what is the actual use of vmstate_dummy ? I had a grep
through and as far as I can see the points where vmstate_cpu_common
is used are all in softmmu-only code. I tried this patch
and QEMU seems to compile OK:

diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 140fa32a5e3..a827417a4d8 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -1131,8 +1131,6 @@ bool target_words_bigendian(void);

 #ifdef CONFIG_SOFTMMU
 extern const VMStateDescription vmstate_cpu_common;
-#else
-#define vmstate_cpu_common vmstate_dummy
 #endif

 #define VMSTATE_CPU() {                                                     \
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 075ee800960..8df7b69f389 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -194,8 +194,6 @@ struct VMStateDescription {
     const VMStateDescription **subsections;
 };

-extern const VMStateDescription vmstate_dummy;
-
 extern const VMStateInfo vmstate_info_bool;

 extern const VMStateInfo vmstate_info_int8;
diff --git a/stubs/vmstate.c b/stubs/vmstate.c
index cc4fe41dfc2..8513d9204e4 100644
--- a/stubs/vmstate.c
+++ b/stubs/vmstate.c
@@ -1,8 +1,6 @@
 #include "qemu/osdep.h"
 #include "migration/vmstate.h"

-const VMStateDescription vmstate_dummy = {};
-
 int vmstate_register_with_alias_id(VMStateIf *obj,
                                    uint32_t instance_id,
                                    const VMStateDescription *vmsd,

thanks
-- PMM