[Qemu-devel] [PATCH v2 2/2] migration: extend migration_bitmap

[Li Zhijian]

Prevously, if we hotplug a device(e.g. device_add e1000) during
migration is processing in source side, qemu will add a new ram
block but migration_bitmap is not extended.
In this case, migration_bitmap will overflow and lead qemu abort
unexpectedly.

Signed-off-by: Li Zhijian <address@hidden>
Signed-off-by: Wen Congyang <address@hidden>
---
 exec.c                  |  5 +++++
 include/exec/exec-all.h |  1 +
 migration/ram.c         | 15 +++++++++++++++
 3 files changed, 21 insertions(+)

diff --git a/exec.c b/exec.c
index f7883d2..1702544 100644
--- a/exec.c
+++ b/exec.c
@@ -1401,6 +1401,11 @@ static ram_addr_t ram_block_add(RAMBlock *new_block, 
Error **errp)
         }
     }
 
+    new_ram_size = MAX(old_ram_size,
+              (new_block->offset + new_block->max_length) >> TARGET_PAGE_BITS);
+    if (new_ram_size > old_ram_size) {
+        migration_bitmap_extend(old_ram_size, new_ram_size);
+    }
     /* Keep the list sorted from biggest to smallest block.  Unlike QTAILQ,
      * QLIST (which has an RCU-friendly variant) does not have insertion at
      * tail, so save the last element in last_block.
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 2573e8c..dd9be44 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -385,4 +385,5 @@ static inline bool cpu_can_do_io(CPUState *cpu)
     return cpu->can_do_io != 0;
 }
 
+void migration_bitmap_extend(ram_addr_t old, ram_addr_t new);
 #endif
diff --git a/migration/ram.c b/migration/ram.c
index 4754aa9..3e16ef8 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1063,6 +1063,21 @@ static void reset_ram_globals(void)
 
 #define MAX_WAIT 50 /* ms, half buffered_file limit */
 
+void migration_bitmap_extend(ram_addr_t old, ram_addr_t new)
+{
+    qemu_mutex_lock(&migration_bitmap_mutex);
+    if (migration_bitmap) {
+        unsigned long *old_bitmap = migration_bitmap, *bitmap;
+        bitmap = bitmap_new(new);
+        bitmap_copy(bitmap, old_bitmap, old);
+        bitmap_set(bitmap, old, new - old);
+        atomic_rcu_set(&migration_bitmap, bitmap);
+        migration_dirty_pages += new - old;
+        synchronize_rcu();
+        g_free(old_bitmap);
+    }
+    qemu_mutex_unlock(&migration_bitmap_mutex);
+}
 
 /* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
  * long-running RCU critical section.  When rcu-reclaims in the code
-- 
2.1.4