[48/49] vmstate: Add suppot for field_exist() test

diff --git a/hw/hw.h b/hw/hw.h
index cabf633..8c223f8 100644
--- a/hw/hw.h
+++ b/hw/hw.h
@@ -10,6 +10,7 @@ 
 #include "cpu-common.h"
 #endif

+#include <stdbool.h>
 #include "ioport.h"
 #include "irq.h"

@@ -299,6 +300,7 @@  typedef struct {
     enum VMStateFlags flags;
     const VMStateDescription *vmsd;
     int version_id;
+    bool (*field_exists)(void *opaque, int version_id);
 } VMStateField;

 struct VMStateDescription {
@@ -345,6 +347,16 @@  extern const VMStateInfo vmstate_info_buffer;
             + type_check(_type,typeof_field(_state, _field))         \
 }

+#define VMSTATE_SINGLE_TEST(_field, _state, _test, _info, _type) {   \
+    .name         = (stringify(_field)),                             \
+    .field_exists = (_test),                                         \
+    .size         = sizeof(_type),                                   \
+    .info         = &(_info),                                        \
+    .flags        = VMS_SINGLE,                                      \
+    .offset       = offsetof(_state, _field)                         \
+            + type_check(_type,typeof_field(_state, _field))         \
+}
+
 #define VMSTATE_POINTER(_field, _state, _version, _info, _type) {    \
     .name       = (stringify(_field)),                               \
     .version_id = (_version),                                        \
@@ -366,6 +378,17 @@  extern const VMStateInfo vmstate_info_buffer;
         + type_check_array(_type,typeof_field(_state, _field),_num)  \
 }

+#define VMSTATE_ARRAY_TEST(_field, _state, _num, _test, _info, _type) {\
+    .name         = (stringify(_field)),                              \
+    .field_exists = (_test),                                          \
+    .num          = (_num),                                           \
+    .info         = &(_info),                                         \
+    .size         = sizeof(_type),                                    \
+    .flags        = VMS_ARRAY,                                        \
+    .offset       = offsetof(_state, _field)                          \
+        + type_check_array(_type,typeof_field(_state, _field),_num)  \
+}
+
 #define VMSTATE_VARRAY(_field, _state, _field_num, _version, _info, _type) {\
     .name       = (stringify(_field)),                               \
     .version_id = (_version),                                        \
@@ -524,6 +547,9 @@  extern const VMStateDescription vmstate_i2c_slave;
 #define VMSTATE_INT32_LE(_f, _s)                                   \
     VMSTATE_SINGLE(_f, _s, 0, vmstate_info_int32_le, int32_t)

+#define VMSTATE_UINT32_TEST(_f, _s, _t)                                  \
+    VMSTATE_SINGLE_TEST(_f, _s, _t, vmstate_info_uint32, uint32_t)
+
 #define VMSTATE_TIMER_V(_f, _s, _v)                                   \
     VMSTATE_POINTER(_f, _s, _v, vmstate_info_timer, QEMUTimer *)

diff --git a/savevm.c b/savevm.c
index 11b331b..7a363b6 100644
--- a/savevm.c
+++ b/savevm.c
@@ -1055,7 +1055,10 @@  int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd,
             return ret;
     }
     while(field->name) {
-        if (field->version_id <= version_id) {
+        if ((field->field_exists &&
+             field->field_exists(opaque, version_id)) ||
+            (!field->field_exists &&
+             field->version_id <= version_id)) {
             void *base_addr = opaque + field->offset;
             int ret, i, n_elems = 1;

@@ -1101,24 +1104,27 @@  void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd,
         vmsd->pre_save(opaque);
     }
     while(field->name) {
-        void *base_addr = opaque + field->offset;
-        int i, n_elems = 1;
+        if (!field->field_exists ||
+            field->field_exists(opaque, vmsd->version_id)) {
+            void *base_addr = opaque + field->offset;
+            int i, n_elems = 1;

-        if (field->flags & VMS_ARRAY) {
-            n_elems = field->num;
-        } else if (field->flags & VMS_VARRAY) {
-            n_elems = *(size_t *)(opaque+field->num_offset);
-        }
-        if (field->flags & VMS_POINTER) {
-            base_addr = *(void **)base_addr;
-        }
-        for (i = 0; i < n_elems; i++) {
-            void *addr = base_addr + field->size * i;
+            if (field->flags & VMS_ARRAY) {
+                n_elems = field->num;
+            } else if (field->flags & VMS_VARRAY) {
+                n_elems = *(size_t *)(opaque+field->num_offset);
+            }
+            if (field->flags & VMS_POINTER) {
+                base_addr = *(void **)base_addr;
+            }
+            for (i = 0; i < n_elems; i++) {
+                void *addr = base_addr + field->size * i;

-            if (field->flags & VMS_STRUCT) {
-                vmstate_save_state(f, field->vmsd, addr);
-            } else {
-                field->info->put(f, addr, field->size);
+                if (field->flags & VMS_STRUCT) {
+                    vmstate_save_state(f, field->vmsd, addr);
+                } else {
+                    field->info->put(f, addr, field->size);
+                }
             }
         }
         field++;