[1/2] migration: allow multifd for socket protocol only

Commit Message

Li Zhijian July 16, 2021, 7:59 a.m. UTC

multifd with unsupported protocal will cause a segment fault.
(gdb) bt
 #0  0x0000563b4a93faf8 in socket_connect (addr=0x0, errp=0x7f7f02675410) at ../util/qemu-sockets.c:1190
 #1  0x0000563b4a797a03 in qio_channel_socket_connect_sync (ioc=0x563b4d16e8c0, addr=0x0, errp=0x7f7f02675410) at ../io/channel-socket.c:145
 #2  0x0000563b4a797abf in qio_channel_socket_connect_worker (task=0x563b4cd86c30, opaque=0x0) at ../io/channel-socket.c:168
 #3  0x0000563b4a792631 in qio_task_thread_worker (opaque=0x563b4cd86c30) at ../io/task.c:124
 #4  0x0000563b4a91da69 in qemu_thread_start (args=0x563b4c44bb80) at ../util/qemu-thread-posix.c:541
 #5  0x00007f7fe9b5b3f9 in ?? ()
 #6  0x0000000000000000 in ?? ()

It's enough to check migrate_multifd_is_allowed() in multifd cleanup() and
multifd setup() though there are so many other places using migrate_use_multifd().

Signed-off-by: Li Zhijian <[e-mail]>
---
 migration/migration.c |  4 ++++
 migration/multifd.c   | 24 ++++++++++++++++++++++--
 migration/multifd.h   |  2 ++
 3 files changed, 28 insertions(+), 2 deletions(-)

Patch

diff --git a/migration/migration.c b/migration/migration.c
index 2d306582ebf..d6d48f6999b 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -456,10 +456,12 @@  static void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p = NULL;
 
+    migrate_protocal_allow_multifd(false); /* reset it anyway */
     qapi_event_send_migration(MIGRATION_STATUS_SETUP);
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
         strstart(uri, "vsock:", NULL)) {
+        migrate_protocal_allow_multifd(true);
         socket_start_incoming_migration(p ? p : uri, errp);
 #ifdef CONFIG_RDMA
     } else if (strstart(uri, "rdma:", &p)) {
@@ -2289,9 +2291,11 @@  void qmp_migrate(const char *uri, bool has_blk, bool blk,
         }
     }
 
+    migrate_protocal_allow_multifd(false);
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
         strstart(uri, "vsock:", NULL)) {
+        migrate_protocal_allow_multifd(true);
         socket_start_outgoing_migration(s, p ? p : uri, &local_err);
 #ifdef CONFIG_RDMA
     } else if (strstart(uri, "rdma:", &p)) {
diff --git a/migration/multifd.c b/migration/multifd.c
index ab41590e714..b3d99c79d83 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -531,7 +531,7 @@  void multifd_save_cleanup(void)
 {
     int i;
 
-    if (!migrate_use_multifd()) {
+    if (!migrate_use_multifd() || !migrate_multifd_is_allowed()) {
         return;
     }
     multifd_send_terminate_threads(NULL);
@@ -864,6 +864,17 @@  cleanup:
     multifd_new_send_channel_cleanup(p, sioc, local_err);
 }
 
+static bool migrate_allow_multifd;
+void migrate_protocal_allow_multifd(bool allow)
+{
+    migrate_allow_multifd = allow;
+}
+
+bool migrate_multifd_is_allowed(void)
+{
+    return migrate_allow_multifd;
+}
+
 int multifd_save_setup(Error **errp)
 {
     int thread_count;
@@ -874,6 +885,11 @@  int multifd_save_setup(Error **errp)
     if (!migrate_use_multifd()) {
         return 0;
     }
+    if (!migrate_multifd_is_allowed()) {
+        error_setg(errp, "multifd is not supported by current protocol");
+        return -1;
+    }
+
     s = migrate_get_current();
     thread_count = migrate_multifd_channels();
     multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
@@ -967,7 +983,7 @@  int multifd_load_cleanup(Error **errp)
 {
     int i;
 
-    if (!migrate_use_multifd()) {
+    if (!migrate_use_multifd() || !migrate_multifd_is_allowed()) {
         return 0;
     }
     multifd_recv_terminate_threads(NULL);
@@ -1123,6 +1139,10 @@  int multifd_load_setup(Error **errp)
     if (!migrate_use_multifd()) {
         return 0;
     }
+    if (!migrate_multifd_is_allowed()) {
+        error_setg(errp, "multifd is not supported by current protocol");
+        return -1;
+    }
     thread_count = migrate_multifd_channels();
     multifd_recv_state = g_malloc0(sizeof(*multifd_recv_state));
     multifd_recv_state->params = g_new0(MultiFDRecvParams, thread_count);
diff --git a/migration/multifd.h b/migration/multifd.h
index 8d6751f5ed8..9d968d63831 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -13,6 +13,8 @@ 
 #ifndef QEMU_MIGRATION_MULTIFD_H
 #define QEMU_MIGRATION_MULTIFD_H
 
+bool migrate_multifd_is_allowed(void);
+void migrate_protocal_allow_multifd(bool allow);
 int multifd_save_setup(Error **errp);
 void multifd_save_cleanup(void);
 int multifd_load_setup(Error **errp);