[PATCH 1/6] migration: Set migration status early in incoming side

[Fabiano Rosas <farosas@suse.de>]

We are sending a migration event of MIGRATION_STATUS_SETUP at
qemu_start_incoming_migration but never actually setting the state.

This creates a window between qmp_migrate_incoming and
process_incoming_migration_co where the migration status is still
MIGRATION_STATUS_NONE. Calling query-migrate during this time will
return an empty response even though the incoming migration command
has already been issued.

Commit 7cf1fe6d68 ("migration: Add migration events on target side")
has added support to the 'events' capability to the incoming part of
migration, but chose to send the SETUP event without setting the
state. I'm assuming this was a mistake.

To avoid introducing a change in behavior, we need to keep sending the
SETUP event, even if the 'events' capability is not set.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/migration.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 7c8292d4d4..562b78261d 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -424,13 +424,26 @@ void migrate_add_address(SocketAddress *address)
 static void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p = NULL;
+    MigrationIncomingState *mis = migration_incoming_get_current();
 
     /* URI is not suitable for migration? */
     if (!migration_channels_and_uri_compatible(uri, errp)) {
         return;
     }
 
-    qapi_event_send_migration(MIGRATION_STATUS_SETUP);
+    migrate_set_state(&mis->state, MIGRATION_STATUS_NONE,
+                      MIGRATION_STATUS_SETUP);
+    /*
+     * QMP clients should have set the 'events' migration capability
+     * if they want to receive this event, in which case the
+     * migrate_set_state() call above will have already sent the
+     * event. We still need to send the event for compatibility even
+     * if migration events are disabled.
+     */
+    if (!migrate_events()) {
+        qapi_event_send_migration(MIGRATION_STATUS_SETUP);
+    }
+
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
         strstart(uri, "vsock:", NULL)) {
@@ -524,7 +537,7 @@ process_incoming_migration_co(void *opaque)
 
     mis->largest_page_size = qemu_ram_pagesize_largest();
     postcopy_state_set(POSTCOPY_INCOMING_NONE);
-    migrate_set_state(&mis->state, MIGRATION_STATUS_NONE,
+    migrate_set_state(&mis->state, MIGRATION_STATUS_SETUP,
                       MIGRATION_STATUS_ACTIVE);
 
     mis->loadvm_co = qemu_coroutine_self();
-- 
2.35.3