postcopy: Incoming initialisation

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
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

@@ -86,6 +86,8 @@ struct MigrationIncomingState {
      */
     QemuEvent main_thread_load_event;
 
+    /* For the kernel to send us notifications */
+    int       userfault_fd;
     QEMUFile *to_src_file;
     QemuMutex rp_mutex;    /* We send replies from multiple threads */
 
@@ -204,6 +206,7 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms);
 /* For incoming postcopy discard */
 int ram_discard_range(MigrationIncomingState *mis, const char *block_name,
                       uint64_t start, size_t length);
+int ram_postcopy_incoming_init(MigrationIncomingState *mis);
 
 /**
  * @migrate_add_blocker - prevent migration from proceeding

include/migration/postcopy-ram.h

@@ -16,6 +16,18 @@
 /* Return true if the host supports everything we need to do postcopy-ram */
 bool postcopy_ram_supported_by_host(void);
 
+/*
+ * Initialise postcopy-ram, setting the RAM to a state where we can go into
+ * postcopy later; must be called prior to any precopy.
+ * called from ram.c's similarly named ram_postcopy_incoming_init
+ */
+int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages);
+
+/*
+ * At the end of a migration where postcopy_ram_incoming_init was called.
+ */
+int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis);
+
 /*
  * Discard the contents of 'length' bytes from 'start'
  * We can assume that if we've been called postcopy_ram_hosttest returned true