[PATCH v2 2/4] migration: Change SaveStateEntry.instance_id into uint32_t

[Peter Xu <peterx@redhat.com>]

It was always used as 32bit, so define it as used to be clear.
Instead of using -1 as the auto-gen magic value, we switch to
UINT32_MAX.  We also make sure that we don't auto-gen this value to
avoid overflowed instance IDs without being noticed.

Suggested-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 hw/intc/apic_common.c        |  2 +-
 include/migration/register.h |  2 +-
 include/migration/vmstate.h  |  6 +++---
 migration/savevm.c           | 18 ++++++++++--------
 stubs/vmstate.c              |  2 +-
 5 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
index 22da53ce8a..fabfa7320b 100644
--- a/hw/intc/apic_common.c
+++ b/hw/intc/apic_common.c
@@ -315,7 +315,7 @@ static void apic_common_realize(DeviceState *dev, Error **errp)
     APICCommonState *s = APIC_COMMON(dev);
     APICCommonClass *info;
     static DeviceState *vapic;
-    int instance_id = s->id;
+    uint32_t instance_id = s->id;
 
     info = APIC_COMMON_GET_CLASS(s);
     info->realize(dev, errp);
diff --git a/include/migration/register.h b/include/migration/register.h
index a13359a08d..f3ba10b6ef 100644
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -69,7 +69,7 @@ typedef struct SaveVMHandlers {
 } SaveVMHandlers;
 
 int register_savevm_live(const char *idstr,
-                         int instance_id,
+                         uint32_t instance_id,
                          int version_id,
                          const SaveVMHandlers *ops,
                          void *opaque);
diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
index c551470299..67bc63e30e 100644
--- a/include/migration/vmstate.h
+++ b/include/migration/vmstate.h
@@ -1113,17 +1113,17 @@ int vmstate_save_state_v(QEMUFile *f, const VMStateDescription *vmsd,
 
 bool vmstate_save_needed(const VMStateDescription *vmsd, void *opaque);
 
-#define  VMSTATE_INSTANCE_ID_ANY  -1
+#define  VMSTATE_INSTANCE_ID_ANY  UINT32_MAX
 
 /* Returns: 0 on success, -1 on failure */
-int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
+int vmstate_register_with_alias_id(DeviceState *dev, uint32_t instance_id,
                                    const VMStateDescription *vmsd,
                                    void *base, int alias_id,
                                    int required_for_version,
                                    Error **errp);
 
 /* Returns: 0 on success, -1 on failure */
-static inline int vmstate_register(DeviceState *dev, int instance_id,
+static inline int vmstate_register(DeviceState *dev, uint32_t instance_id,
                                    const VMStateDescription *vmsd,
                                    void *opaque)
 {
diff --git a/migration/savevm.c b/migration/savevm.c
index 0074572a52..1e44f06d7a 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -233,7 +233,7 @@ typedef struct CompatEntry {
 typedef struct SaveStateEntry {
     QTAILQ_ENTRY(SaveStateEntry) entry;
     char idstr[256];
-    int instance_id;
+    uint32_t instance_id;
     int alias_id;
     int version_id;
     /* version id read from the stream */
@@ -665,10 +665,10 @@ void dump_vmstate_json_to_file(FILE *out_file)
     fclose(out_file);
 }
 
-static int calculate_new_instance_id(const char *idstr)
+static uint32_t calculate_new_instance_id(const char *idstr)
 {
     SaveStateEntry *se;
-    int instance_id = 0;
+    uint32_t instance_id = 0;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (strcmp(idstr, se->idstr) == 0
@@ -676,6 +676,8 @@ static int calculate_new_instance_id(const char *idstr)
             instance_id = se->instance_id + 1;
         }
     }
+    /* Make sure we never loop over without being noticed */
+    assert(instance_id != VMSTATE_INSTANCE_ID_ANY);
     return instance_id;
 }
 
@@ -730,7 +732,7 @@ static void savevm_state_handler_insert(SaveStateEntry *nse)
    Meanwhile pass -1 as instance_id if you do not already have a clearly
    distinguishing id for all instances of your device class. */
 int register_savevm_live(const char *idstr,
-                         int instance_id,
+                         uint32_t instance_id,
                          int version_id,
                          const SaveVMHandlers *ops,
                          void *opaque)
@@ -784,7 +786,7 @@ void unregister_savevm(DeviceState *dev, const char *idstr, void *opaque)
     }
 }
 
-int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
+int vmstate_register_with_alias_id(DeviceState *dev, uint32_t instance_id,
                                    const VMStateDescription *vmsd,
                                    void *opaque, int alias_id,
                                    int required_for_version,
@@ -1566,7 +1568,7 @@ int qemu_save_device_state(QEMUFile *f)
     return qemu_file_get_error(f);
 }
 
-static SaveStateEntry *find_se(const char *idstr, int instance_id)
+static SaveStateEntry *find_se(const char *idstr, uint32_t instance_id)
 {
     SaveStateEntry *se;
 
@@ -2235,7 +2237,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, MigrationIncomingState *mis)
     /* Find savevm section */
     se = find_se(idstr, instance_id);
     if (se == NULL) {
-        error_report("Unknown savevm section or instance '%s' %d. "
+        error_report("Unknown savevm section or instance '%s' %"PRIu32". "
                      "Make sure that your current VM setup matches your "
                      "saved VM setup, including any hotplugged devices",
                      idstr, instance_id);
@@ -2259,7 +2261,7 @@ qemu_loadvm_section_start_full(QEMUFile *f, MigrationIncomingState *mis)
 
     ret = vmstate_load(f, se);
     if (ret < 0) {
-        error_report("error while loading state for instance 0x%x of"
+        error_report("error while loading state for instance 0x%"PRIx32" of"
                      " device '%s'", instance_id, idstr);
         return ret;
     }
diff --git a/stubs/vmstate.c b/stubs/vmstate.c
index e1e89b87f0..4ed5cc6e9e 100644
--- a/stubs/vmstate.c
+++ b/stubs/vmstate.c
@@ -4,7 +4,7 @@
 const VMStateDescription vmstate_dummy = {};
 
 int vmstate_register_with_alias_id(DeviceState *dev,
-                                   int instance_id,
+                                   uint32_t instance_id,
                                    const VMStateDescription *vmsd,
                                    void *base, int alias_id,
                                    int required_for_version,
-- 
2.21.0