[PATCH v3 4/6] 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.

This introduces a change in behavior, any QMP client waiting for the
SETUP event will hang, unless it has previously enabled the 'events'
capability. Having the capability enabled is sufficient to continue to
receive the event.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/migration.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 92ad9f2470..f2d2782101 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -425,13 +425,16 @@ 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);
+
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
         strstart(uri, "vsock:", NULL)) {
@@ -525,7 +528,7 @@ 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