migration: Add configuration section

It needs to be the first one and it is not optional, that is the reason
why it is opencoded.  For new machine types, it is required that machine
type name is the same in both sides.

It is just done right now for pc's.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

4 files changed, 65 insertions, 0 deletions

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 3ee3b47cec..4c3cb40ce0 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -313,6 +313,7 @@ static void pc_compat_2_3(MachineState *machine)
         pcms->smm = ON_OFF_AUTO_OFF;
     }
     global_state_set_optional();
+    savevm_skip_configuration();
 }
 
 static void pc_compat_2_2(MachineState *machine)
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 0dc4ab149a..43e6c18777 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -296,6 +296,7 @@ static void pc_compat_2_3(MachineState *machine)
         pcms->smm = ON_OFF_AUTO_OFF;
     }
     global_state_set_optional();
+    savevm_skip_configuration();
 }
 
 static void pc_compat_2_2(MachineState *machine)
diff --git a/include/migration/migration.h b/include/migration/migration.h
index f153eba47a..a308eccf18 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -34,6 +34,7 @@
 #define QEMU_VM_SECTION_FULL         0x04
 #define QEMU_VM_SUBSECTION           0x05
 #define QEMU_VM_VMDESCRIPTION        0x06
+#define QEMU_VM_CONFIGURATION        0x07
 #define QEMU_VM_SECTION_FOOTER       0x7e
 
 struct MigrationParams {
@@ -199,4 +200,5 @@ void ram_mig_init(void);
 void savevm_skip_section_footers(void);
 void register_global_state(void);
 void global_state_set_optional(void);
+void savevm_skip_configuration(void);
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index e779c96ef9..b28a2694ad 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -246,11 +246,55 @@ typedef struct SaveStateEntry {
 typedef struct SaveState {
     QTAILQ_HEAD(, SaveStateEntry) handlers;
     int global_section_id;
+    bool skip_configuration;
+    uint32_t len;
+    const char *name;
 } SaveState;
 
 static SaveState savevm_state = {
     .handlers = QTAILQ_HEAD_INITIALIZER(savevm_state.handlers),
     .global_section_id = 0,
+    .skip_configuration = false,
+};
+
+void savevm_skip_configuration(void)
+{
+    savevm_state.skip_configuration = true;
+}
+
+
+static void configuration_pre_save(void *opaque)
+{
+    SaveState *state = opaque;
+    const char *current_name = MACHINE_GET_CLASS(current_machine)->name;
+
+    state->len = strlen(current_name);
+    state->name = current_name;
+}
+
+static int configuration_post_load(void *opaque, int version_id)
+{
+    SaveState *state = opaque;
+    const char *current_name = MACHINE_GET_CLASS(current_machine)->name;
+
+    if (strncmp(state->name, current_name, state->len) != 0) {
+        error_report("Machine type received is '%s' and local is '%s'",
+                     state->name, current_name);
+        return -EINVAL;
+    }
+    return 0;
+}
+
+static const VMStateDescription vmstate_configuration = {
+    .name = "configuration",
+    .version_id = 1,
+    .post_load = configuration_post_load,
+    .pre_save = configuration_pre_save,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(len, SaveState),
+        VMSTATE_VBUFFER_ALLOC_UINT32(name, SaveState, 0, NULL, 0, len),
+        VMSTATE_END_OF_LIST()
+    },
 };
 
 static void dump_vmstate_vmsd(FILE *out_file,
@@ -723,6 +767,11 @@ void qemu_savevm_state_begin(QEMUFile *f,
         se->ops->set_params(params, se->opaque);
     }
 
+    if (!savevm_state.skip_configuration) {
+        qemu_put_byte(f, QEMU_VM_CONFIGURATION);
+        vmstate_save_state(f, &vmstate_configuration, &savevm_state, 0);
+    }
+
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (!se->ops || !se->ops->save_live_setup) {
             continue;
@@ -1037,6 +1086,18 @@ int qemu_loadvm_state(QEMUFile *f)
         return -ENOTSUP;
     }
 
+    if (!savevm_state.skip_configuration) {
+        if (qemu_get_byte(f) != QEMU_VM_CONFIGURATION) {
+            error_report("Configuration section missing");
+            return -EINVAL;
+        }
+        ret = vmstate_load_state(f, &vmstate_configuration, &savevm_state, 0);
+
+        if (ret) {
+            return ret;
+        }
+    }
+
     while ((section_type = qemu_get_byte(f)) != QEMU_VM_EOF) {
         uint32_t instance_id, version_id, section_id;
         SaveStateEntry *se;