[Qemu-devel] [PATCH 9/9] migration: Add configuration section

[Juan Quintela]

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 than machine
type name is the same in both sides.

It is just done right now for pc's.

Signed-off-by: Juan Quintela <address@hidden>
---
 hw/i386/pc_piix.c             |  1 +
 hw/i386/pc_q35.c              |  1 +
 include/migration/migration.h |  2 ++
 savevm.c                      | 72 ++++++++++++++++++++++++++++++++++++++++---
 4 files changed, 71 insertions(+), 5 deletions(-)

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 5c04784..95806b3 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -314,6 +314,7 @@ static void pc_init_pci(MachineState *machine)
 static void pc_compat_2_3(MachineState *machine)
 {
     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 cc5827a..e32c040 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -293,6 +293,7 @@ static void pc_q35_init(MachineState *machine)
 static void pc_compat_2_3(MachineState *machine)
 {
     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 f939d88..da89827 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

 struct MigrationParams {
     bool blk;
@@ -184,4 +185,5 @@ void register_global_state(void);
 void global_state_store(void);
 char *global_state_get_runstate(void);
 void global_state_set_optional(void);
+void savevm_skip_configuration(void);
 #endif
diff --git a/savevm.c b/savevm.c
index 2b4e554..ea149e7 100644
--- a/savevm.c
+++ b/savevm.c
@@ -238,11 +238,55 @@ typedef struct SaveStateEntry {
 typedef struct SaveState {
     QTAILQ_HEAD(, SaveStateEntry) handlers;
     int global_section_id;
+    bool skip_configuration;
+    uint32_t len;
+    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 = strdup(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 = "configuartion",
+    .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,
@@ -625,7 +669,7 @@ void qemu_savevm_state_begin(QEMUFile *f,
                              const MigrationParams *params)
 {
     SaveStateEntry *se;
-    int ret;
+    int ret, len;

     trace_savevm_state_begin();
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
@@ -638,9 +682,13 @@ void qemu_savevm_state_begin(QEMUFile *f,
     qemu_put_be32(f, QEMU_VM_FILE_MAGIC);
     qemu_put_be32(f, QEMU_VM_FILE_VERSION);

-    QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
-        int len;
+    /* We want this to be the 1st section on the migration stream */
+    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;
         }
@@ -946,7 +994,7 @@ int qemu_loadvm_state(QEMUFile *f)
     Error *local_err = NULL;
     uint8_t section_type;
     unsigned int v;
-    int ret;
+    int ret, len;
     int file_error_after_eof = -1;

     if (qemu_savevm_state_blocked(&local_err)) {
@@ -970,11 +1018,25 @@ int qemu_loadvm_state(QEMUFile *f)
         return -ENOTSUP;
     }

+    /* if it exist, we want the configuration to be the 1st section
+       and we require it to be there.  That is the reason why we don't
+       read it on the while loop. */
+    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;
         char idstr[257];
-        int len;

         trace_qemu_loadvm_state_section(section_type);
         switch (section_type) {
-- 
2.4.0