migration: Make VMStateDescription.subsections const

Allow the array of pointers to itself be const.
Propagate this through the copies of this field.

Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20231221031652.119827-2-richard.henderson@linaro.org>

3 files changed, 15 insertions, 13 deletions

diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index 9821918631..294d2d8486 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -209,7 +209,7 @@ struct VMStateDescription {
     bool (*dev_unplug_pending)(void *opaque);
 
     const VMStateField *fields;
-    const VMStateDescription **subsections;
+    const VMStateDescription * const *subsections;
 };
 
 extern const VMStateInfo vmstate_info_bool;
diff --git a/migration/savevm.c b/migration/savevm.c
index 1b9ab7b8ee..eab62330b6 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -551,11 +551,11 @@ static void dump_vmstate_vmsf(FILE *out_file, const VMStateField *field,
 }
 
 static void dump_vmstate_vmss(FILE *out_file,
-                              const VMStateDescription **subsection,
+                              const VMStateDescription *subsection,
                               int indent)
 {
-    if (*subsection != NULL) {
-        dump_vmstate_vmsd(out_file, *subsection, indent, true);
+    if (subsection != NULL) {
+        dump_vmstate_vmsd(out_file, subsection, indent, true);
     }
 }
 
@@ -597,7 +597,7 @@ static void dump_vmstate_vmsd(FILE *out_file,
         fprintf(out_file, "\n%*s]", indent, "");
     }
     if (vmsd->subsections != NULL) {
-        const VMStateDescription **subsection = vmsd->subsections;
+        const VMStateDescription * const *subsection = vmsd->subsections;
         bool first;
 
         fprintf(out_file, ",\n%*s\"Subsections\": [\n", indent, "");
@@ -606,7 +606,7 @@ static void dump_vmstate_vmsd(FILE *out_file,
             if (!first) {
                 fprintf(out_file, ",\n");
             }
-            dump_vmstate_vmss(out_file, subsection, indent + 2);
+            dump_vmstate_vmss(out_file, *subsection, indent + 2);
             subsection++;
             first = false;
         }
@@ -831,7 +831,7 @@ void unregister_savevm(VMStateIf *obj, const char *idstr, void *opaque)
 static void vmstate_check(const VMStateDescription *vmsd)
 {
     const VMStateField *field = vmsd->fields;
-    const VMStateDescription **subsection = vmsd->subsections;
+    const VMStateDescription * const *subsection = vmsd->subsections;
 
     if (field) {
         while (field->name) {
diff --git a/migration/vmstate.c b/migration/vmstate.c
index b7723a4187..ef26f26ccd 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -452,13 +452,15 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
 }
 
 static const VMStateDescription *
-vmstate_get_subsection(const VMStateDescription **sub, char *idstr)
+vmstate_get_subsection(const VMStateDescription * const *sub,
+                       const char *idstr)
 {
-    while (sub && *sub) {
-        if (strcmp(idstr, (*sub)->name) == 0) {
-            return *sub;
+    if (sub) {
+        for (const VMStateDescription *s = *sub; s ; s = *++sub) {
+            if (strcmp(idstr, s->name) == 0) {
+                return s;
+            }
         }
-        sub++;
     }
     return NULL;
 }
@@ -517,7 +519,7 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,
 static int vmstate_subsection_save(QEMUFile *f, const VMStateDescription *vmsd,
                                    void *opaque, JSONWriter *vmdesc)
 {
-    const VMStateDescription **sub = vmsd->subsections;
+    const VMStateDescription * const *sub = vmsd->subsections;
     bool vmdesc_has_subsections = false;
     int ret = 0;