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[PULL,05/13] migration: Fix a potential issue

Message ID 5533b2e9bcd222e37ca6c2ff06e79adf9bf036bf.1466168448.git.amit.shah@redhat.com
State New
Headers show

Commit Message

Amit Shah June 17, 2016, 1:06 p.m. UTC 
From: 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>
Suggested-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Liang Li <liang.z.li@intel.com>
Message-Id: <1462433579-13691-3-git-send-email-liang.z.li@intel.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 migration/ram.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
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Patch

diff --git a/migration/ram.c b/migration/ram.c
index f3fe6c7..5ccc068 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2223,6 +2223,24 @@  static void *do_data_decompress(void *opaque)
     return NULL;
 }
 
+static void wait_for_decompress_done(void)
+{
+    int idx, thread_count;
+
+    if (!migrate_use_compression()) {
+        return;
+    }
+
+    thread_count = migrate_decompress_threads();
+    qemu_mutex_lock(&decomp_done_lock);
+    for (idx = 0; idx < thread_count; idx++) {
+        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;
@@ -2557,6 +2575,7 @@  static int ram_load(QEMUFile *f, void *opaque, int version_id)
         }
     }
 
+    wait_for_decompress_done();
     rcu_read_unlock();
     DPRINTF("Completed load of VM with exit code %d seq iteration "
             "%" PRIu64 "\n", ret, seq_iter);