[Qemu-devel] [PATCH 2/5] migration: Fix a potential issue

[Liang Li <liang.z.li@intel.com>]

At the end of live migration and before vm_start() on the destination
side, we should make sure all the decompression tasks are finished, if
this can not be guaranteed, the VM may get the incorrect memory data,
or the updated memory may be overwritten by the decompression thread.
Add the code to fix this potential issue.

Suggested-by: David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Liang Li <liang.z.li@intel.com>
---
 include/migration/migration.h |  1 +
 migration/migration.c         |  2 +-
 migration/ram.c               | 20 ++++++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/include/migration/migration.h b/include/migration/migration.h
index ac2c12c..1c9051e 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -223,6 +223,7 @@ void migrate_compress_threads_create(void);
 void migrate_compress_threads_join(void);
 void migrate_decompress_threads_create(void);
 void migrate_decompress_threads_join(void);
+void wait_for_decompress_done(void);
 uint64_t ram_bytes_remaining(void);
 uint64_t ram_bytes_transferred(void);
 uint64_t ram_bytes_total(void);
diff --git a/migration/migration.c b/migration/migration.c
index 991313a..5228c28 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -347,7 +347,7 @@ static void process_incoming_migration_bh(void *opaque)
     /* If global state section was not received or we are in running
        state, we need to obey autostart. Any other state is set with
        runstate_set. */
-
+    wait_for_decompress_done();
     if (!global_state_received() ||
         global_state_get_runstate() == RUN_STATE_RUNNING) {
         if (autostart) {
diff --git a/migration/ram.c b/migration/ram.c
index 7ab6ab5..4459b38 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2220,6 +2220,26 @@ static void *do_data_decompress(void *opaque)
     return NULL;
 }
 
+void wait_for_decompress_done(void)
+{
+    int idx, thread_count;
+
+    if (!migrate_use_compression()) {
+        return;
+    }
+    thread_count = migrate_decompress_threads();
+    for (idx = 0; idx < thread_count; idx++) {
+        if (!decomp_param[idx].done) {
+            qemu_mutex_lock(&decomp_done_lock);
+            while (!decomp_param[idx].done) {
+                qemu_cond_wait(&decomp_done_cond, &decomp_done_lock);
+            }
+            qemu_mutex_unlock(&decomp_done_lock);
+        }
+    }
+
+}
+
 void migrate_decompress_threads_create(void)
 {
     int i, thread_count;
-- 
1.9.1