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-rw-r--r--migration/channel.c45
-rw-r--r--migration/channel.h5
-rw-r--r--migration/migration.c54
-rw-r--r--migration/multifd.c19
-rw-r--r--migration/multifd.h2
-rw-r--r--migration/postcopy-ram.c5
-rw-r--r--migration/postcopy-ram.h2
7 files changed, 101 insertions, 31 deletions
diff --git a/migration/channel.c b/migration/channel.c
index 1b0815039f..ca3319a309 100644
--- a/migration/channel.c
+++ b/migration/channel.c
@@ -92,3 +92,48 @@ void migration_channel_connect(MigrationState *s,
     migrate_fd_connect(s, error);
     error_free(error);
 }
+
+
+/**
+ * @migration_channel_read_peek - Peek at migration channel, without
+ *     actually removing it from channel buffer.
+ *
+ * @ioc: the channel object
+ * @buf: the memory region to read data into
+ * @buflen: the number of bytes to read in @buf
+ * @errp: pointer to a NULL-initialized error object
+ *
+ * Returns 0 if successful, returns -1 and sets @errp if fails.
+ */
+int migration_channel_read_peek(QIOChannel *ioc,
+                                const char *buf,
+                                const size_t buflen,
+                                Error **errp)
+{
+    ssize_t len = 0;
+    struct iovec iov = { .iov_base = (char *)buf, .iov_len = buflen };
+
+    while (true) {
+        len = qio_channel_readv_full(ioc, &iov, 1, NULL, NULL,
+                                     QIO_CHANNEL_READ_FLAG_MSG_PEEK, errp);
+
+        if (len <= 0 && len != QIO_CHANNEL_ERR_BLOCK) {
+            error_setg(errp,
+                       "Failed to peek at channel");
+            return -1;
+        }
+
+        if (len == buflen) {
+            break;
+        }
+
+        /* 1ms sleep. */
+        if (qemu_in_coroutine()) {
+            qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000);
+        } else {
+            g_usleep(1000);
+        }
+    }
+
+    return 0;
+}
diff --git a/migration/channel.h b/migration/channel.h
index 67a461c28a..5bdb8208a7 100644
--- a/migration/channel.h
+++ b/migration/channel.h
@@ -24,4 +24,9 @@ void migration_channel_connect(MigrationState *s,
                                QIOChannel *ioc,
                                const char *hostname,
                                Error *error_in);
+
+int migration_channel_read_peek(QIOChannel *ioc,
+                                const char *buf,
+                                const size_t buflen,
+                                Error **errp);
 #endif
diff --git a/migration/migration.c b/migration/migration.c
index 4f4d798d3e..66c74f8e17 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -31,6 +31,7 @@
 #include "migration.h"
 #include "savevm.h"
 #include "qemu-file.h"
+#include "channel.h"
 #include "migration/vmstate.h"
 #include "block/block.h"
 #include "qapi/error.h"
@@ -664,10 +665,6 @@ static bool migration_incoming_setup(QEMUFile *f, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
-    if (multifd_load_setup(errp) != 0) {
-        return false;
-    }
-
     if (!mis->from_src_file) {
         mis->from_src_file = f;
     }
@@ -734,31 +731,56 @@ void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
     Error *local_err = NULL;
-    bool start_migration;
     QEMUFile *f;
+    bool default_channel = true;
+    uint32_t channel_magic = 0;
+    int ret = 0;
 
-    if (!mis->from_src_file) {
-        /* The first connection (multifd may have multiple) */
+    if (migrate_use_multifd() && !migrate_postcopy_ram() &&
+        qio_channel_has_feature(ioc, QIO_CHANNEL_FEATURE_READ_MSG_PEEK)) {
+        /*
+         * With multiple channels, it is possible that we receive channels
+         * out of order on destination side, causing incorrect mapping of
+         * source channels on destination side. Check channel MAGIC to
+         * decide type of channel. Please note this is best effort, postcopy
+         * preempt channel does not send any magic number so avoid it for
+         * postcopy live migration. Also tls live migration already does
+         * tls handshake while initializing main channel so with tls this
+         * issue is not possible.
+         */
+        ret = migration_channel_read_peek(ioc, (void *)&channel_magic,
+                                          sizeof(channel_magic), &local_err);
+
+        if (ret != 0) {
+            error_propagate(errp, local_err);
+            return;
+        }
+
+        default_channel = (channel_magic == cpu_to_be32(QEMU_VM_FILE_MAGIC));
+    } else {
+        default_channel = !mis->from_src_file;
+    }
+
+    if (multifd_load_setup(errp) != 0) {
+        error_setg(errp, "Failed to setup multifd channels");
+        return;
+    }
+
+    if (default_channel) {
         f = qemu_file_new_input(ioc);
 
         if (!migration_incoming_setup(f, errp)) {
             return;
         }
-
-        /*
-         * Common migration only needs one channel, so we can start
-         * right now.  Some features need more than one channel, we wait.
-         */
-        start_migration = !migration_needs_multiple_sockets();
     } else {
         /* Multiple connections */
         assert(migration_needs_multiple_sockets());
         if (migrate_use_multifd()) {
-            start_migration = multifd_recv_new_channel(ioc, &local_err);
+            multifd_recv_new_channel(ioc, &local_err);
         } else {
             assert(migrate_postcopy_preempt());
             f = qemu_file_new_input(ioc);
-            start_migration = postcopy_preempt_new_channel(mis, f);
+            postcopy_preempt_new_channel(mis, f);
         }
         if (local_err) {
             error_propagate(errp, local_err);
@@ -766,7 +788,7 @@ void migration_ioc_process_incoming(QIOChannel *ioc, Error **errp)
         }
     }
 
-    if (start_migration) {
+    if (migration_has_all_channels()) {
         /* If it's a recovery, we're done */
         if (postcopy_try_recover()) {
             return;
diff --git a/migration/multifd.c b/migration/multifd.c
index 000ca4d4ec..eeb4fb87ee 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -1164,9 +1164,14 @@ int multifd_load_setup(Error **errp)
     uint32_t page_count = MULTIFD_PACKET_SIZE / qemu_target_page_size();
     uint8_t i;
 
-    if (!migrate_use_multifd()) {
+    /*
+     * Return successfully if multiFD recv state is already initialised
+     * or multiFD is not enabled.
+     */
+    if (multifd_recv_state || !migrate_use_multifd()) {
         return 0;
     }
+
     if (!migrate_multi_channels_is_allowed()) {
         error_setg(errp, "multifd is not supported by current protocol");
         return -1;
@@ -1227,11 +1232,9 @@ bool multifd_recv_all_channels_created(void)
 
 /*
  * Try to receive all multifd channels to get ready for the migration.
- * - Return true and do not set @errp when correctly receiving all channels;
- * - Return false and do not set @errp when correctly receiving the current one;
- * - Return false and set @errp when failing to receive the current channel.
+ * Sets @errp when failing to receive the current channel.
  */
-bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
+void multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
 {
     MultiFDRecvParams *p;
     Error *local_err = NULL;
@@ -1244,7 +1247,7 @@ bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
                                 "failed to receive packet"
                                 " via multifd channel %d: ",
                                 qatomic_read(&multifd_recv_state->count));
-        return false;
+        return;
     }
     trace_multifd_recv_new_channel(id);
 
@@ -1254,7 +1257,7 @@ bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
                    id);
         multifd_recv_terminate_threads(local_err);
         error_propagate(errp, local_err);
-        return false;
+        return;
     }
     p->c = ioc;
     object_ref(OBJECT(ioc));
@@ -1265,6 +1268,4 @@ bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp)
     qemu_thread_create(&p->thread, p->name, multifd_recv_thread, p,
                        QEMU_THREAD_JOINABLE);
     qatomic_inc(&multifd_recv_state->count);
-    return qatomic_read(&multifd_recv_state->count) ==
-           migrate_multifd_channels();
 }
diff --git a/migration/multifd.h b/migration/multifd.h
index e2802a9ce2..ff3aa2e2e9 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -18,7 +18,7 @@ void multifd_save_cleanup(void);
 int multifd_load_setup(Error **errp);
 int multifd_load_cleanup(Error **errp);
 bool multifd_recv_all_channels_created(void);
-bool multifd_recv_new_channel(QIOChannel *ioc, Error **errp);
+void multifd_recv_new_channel(QIOChannel *ioc, Error **errp);
 void multifd_recv_sync_main(void);
 int multifd_send_sync_main(QEMUFile *f);
 int multifd_queue_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset);
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index 0c55df0e52..b98e95dab0 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -1538,7 +1538,7 @@ void postcopy_unregister_shared_ufd(struct PostCopyFD *pcfd)
     }
 }
 
-bool postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file)
+void postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file)
 {
     /*
      * The new loading channel has its own threads, so it needs to be
@@ -1547,9 +1547,6 @@ bool postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file)
     qemu_file_set_blocking(file, true);
     mis->postcopy_qemufile_dst = file;
     trace_postcopy_preempt_new_channel();
-
-    /* Start the migration immediately */
-    return true;
 }
 
 /*
diff --git a/migration/postcopy-ram.h b/migration/postcopy-ram.h
index 6147bf7d1d..25881c4127 100644
--- a/migration/postcopy-ram.h
+++ b/migration/postcopy-ram.h
@@ -190,7 +190,7 @@ enum PostcopyChannels {
     RAM_CHANNEL_MAX,
 };
 
-bool postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file);
+void postcopy_preempt_new_channel(MigrationIncomingState *mis, QEMUFile *file);
 int postcopy_preempt_setup(MigrationState *s, Error **errp);
 int postcopy_preempt_wait_channel(MigrationState *s);