Add wrappers and handlers for sending/receiving the postcopy-ram migr…

…ation messages.

The state of the postcopy process is managed via a series of messages;
   * Add wrappers and handlers for sending/receiving these messages
   * Add state variable that track the current state of postcopy

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

include/migration/migration.h

@@ -53,6 +53,29 @@ enum mig_rp_message_type {
 };
 
 typedef QLIST_HEAD(, LoadStateEntry) LoadStateEntry_Head;
+
+/* The current postcopy state is read/set by postcopy_state_get/set
+ * which update it atomically.
+ * The state is updated as postcopy messages are received, and
+ * in general only one thread should be writing to the state at any one
+ * time, initially the main thread and then the listen thread;
+ * Corner cases are where either thread finishes early and/or errors.
+ * The state is checked as messages are received to ensure that
+ * the source is sending us messages in the correct order.
+ * The state is also used by the RAM reception code to know if it
+ * has to place pages atomically, and the cleanup code at the end of
+ * the main thread to know if it has to delay cleanup until the end
+ * of postcopy.
+ */
+typedef enum {
+    POSTCOPY_INCOMING_NONE = 0,  /* Initial state - no postcopy */
+    POSTCOPY_INCOMING_ADVISE,
+    POSTCOPY_INCOMING_DISCARD,
+    POSTCOPY_INCOMING_LISTENING,
+    POSTCOPY_INCOMING_RUNNING,
+    POSTCOPY_INCOMING_END
+} PostcopyState;
+
 /* State for the incoming migration */
 struct MigrationIncomingState {
     QEMUFile *from_src_file;
@@ -240,4 +263,8 @@ void global_state_set_optional(void);
 void savevm_skip_configuration(void);
 int global_state_store(void);
 void global_state_store_running(void);
+
+PostcopyState postcopy_state_get(void);
+/* Set the state and return the old state */
+PostcopyState postcopy_state_set(PostcopyState new_state);
 #endif

include/sysemu/sysemu.h

@@ -89,6 +89,16 @@ enum qemu_vm_cmd {
     MIG_CMD_INVALID = 0,   /* Must be 0 */
     MIG_CMD_OPEN_RETURN_PATH,  /* Tell the dest to open the Return path */
     MIG_CMD_PING,              /* Request a PONG on the RP */
+
+    MIG_CMD_POSTCOPY_ADVISE,       /* Prior to any page transfers, just
+                                      warn we might want to do PC */
+    MIG_CMD_POSTCOPY_LISTEN,       /* Start listening for incoming
+                                      pages as it's running. */
+    MIG_CMD_POSTCOPY_RUN,          /* Start execution */
+
+    MIG_CMD_POSTCOPY_RAM_DISCARD,  /* A list of pages to discard that
+                                      were previously sent during
+                                      precopy but are dirty. */
     MIG_CMD_MAX
 };
 
@@ -104,6 +114,15 @@ void qemu_savevm_command_send(QEMUFile *f, enum qemu_vm_cmd command,
                               uint16_t len, uint8_t *data);
 void qemu_savevm_send_ping(QEMUFile *f, uint32_t value);
 void qemu_savevm_send_open_return_path(QEMUFile *f);
+void qemu_savevm_send_postcopy_advise(QEMUFile *f);
+void qemu_savevm_send_postcopy_listen(QEMUFile *f);
+void qemu_savevm_send_postcopy_run(QEMUFile *f);
+
+void qemu_savevm_send_postcopy_ram_discard(QEMUFile *f, const char *name,
+                                           uint16_t len,
+                                           uint64_t *start_list,
+                                           uint64_t *length_list);
+
 int qemu_loadvm_state(QEMUFile *f);
 
 typedef enum DisplayType

migration/migration.c

@@ -57,6 +57,13 @@ static NotifierList migration_state_notifiers =
 
 static bool deferred_incoming;
 
+/*
+ * Current state of incoming postcopy; note this is not part of
+ * MigrationIncomingState since it's state is used during cleanup
+ * at the end as MIS is being freed.
+ */
+static PostcopyState incoming_postcopy_state;
+
 /* When we add fault tolerance, we could have several
    migrations at once.  For now we don't need to add
    dynamic creation of migration */
@@ -284,6 +291,7 @@ static void process_incoming_migration_co(void *opaque)
     int ret;
 
     migration_incoming_state_new(f);
+    postcopy_state_set(POSTCOPY_INCOMING_NONE);
     migrate_generate_event(MIGRATION_STATUS_ACTIVE);
     ret = qemu_loadvm_state(f);
 
@@ -1367,3 +1375,15 @@ void migrate_fd_connect(MigrationState *s)
     qemu_thread_create(&s->thread, "migration", migration_thread, s,
                        QEMU_THREAD_JOINABLE);
 }
+
+PostcopyState  postcopy_state_get(void)
+{
+    return atomic_mb_read(&incoming_postcopy_state);
+}
+
+/* Set the state and return the old state */
+PostcopyState postcopy_state_set(PostcopyState new_state)
+{
+    return atomic_xchg(&incoming_postcopy_state, new_state);
+}
+