migration: new message MIG_RP_MSG_RESUME_ACK

Creating new message to reply for MIG_CMD_POSTCOPY_RESUME. One uint32_t
is used as payload to let the source know whether destination is ready
to continue the migration.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-15-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

1 files changed, 37 insertions, 0 deletions

diff --git a/migration/migration.c b/migration/migration.c
index 7c5e20b3f6..4f2c6d22d1 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -96,6 +96,7 @@ enum mig_rp_message_type {
     MIG_RP_MSG_REQ_PAGES_ID, /* data (start: be64, len: be32, id: string) */
     MIG_RP_MSG_REQ_PAGES,    /* data (start: be64, len: be32) */
     MIG_RP_MSG_RECV_BITMAP,  /* send recved_bitmap back to source */
+    MIG_RP_MSG_RESUME_ACK,   /* tell source that we are ready to resume */
 
     MIG_RP_MSG_MAX
 };
@@ -564,6 +565,14 @@ void migrate_send_rp_recv_bitmap(MigrationIncomingState *mis,
     trace_migrate_send_rp_recv_bitmap(block_name, res);
 }
 
+void migrate_send_rp_resume_ack(MigrationIncomingState *mis, uint32_t value)
+{
+    uint32_t buf;
+
+    buf = cpu_to_be32(value);
+    migrate_send_rp_message(mis, MIG_RP_MSG_RESUME_ACK, sizeof(buf), &buf);
+}
+
 MigrationCapabilityStatusList *qmp_query_migrate_capabilities(Error **errp)
 {
     MigrationCapabilityStatusList *head = NULL;
@@ -1843,6 +1852,7 @@ static struct rp_cmd_args {
     [MIG_RP_MSG_REQ_PAGES]      = { .len = 12, .name = "REQ_PAGES" },
     [MIG_RP_MSG_REQ_PAGES_ID]   = { .len = -1, .name = "REQ_PAGES_ID" },
     [MIG_RP_MSG_RECV_BITMAP]    = { .len = -1, .name = "RECV_BITMAP" },
+    [MIG_RP_MSG_RESUME_ACK]     = { .len =  4, .name = "RESUME_ACK" },
     [MIG_RP_MSG_MAX]            = { .len = -1, .name = "MAX" },
 };
 
@@ -1900,6 +1910,25 @@ static int migrate_handle_rp_recv_bitmap(MigrationState *s, char *block_name)
     return ram_dirty_bitmap_reload(s, block);
 }
 
+static int migrate_handle_rp_resume_ack(MigrationState *s, uint32_t value)
+{
+    trace_source_return_path_thread_resume_ack(value);
+
+    if (value != MIGRATION_RESUME_ACK_VALUE) {
+        error_report("%s: illegal resume_ack value %"PRIu32,
+                     __func__, value);
+        return -1;
+    }
+
+    /* Now both sides are active. */
+    migrate_set_state(&s->state, MIGRATION_STATUS_POSTCOPY_RECOVER,
+                      MIGRATION_STATUS_POSTCOPY_ACTIVE);
+
+    /* TODO: notify send thread that time to continue send pages */
+
+    return 0;
+}
+
 /*
  * Handles messages sent on the return path towards the source VM
  *
@@ -2019,6 +2048,14 @@ retry:
             }
             break;
 
+        case MIG_RP_MSG_RESUME_ACK:
+            tmp32 = ldl_be_p(buf);
+            if (migrate_handle_rp_resume_ack(ms, tmp32)) {
+                mark_source_rp_bad(ms);
+                goto out;
+            }
+            break;
+
         default:
             break;
         }