[Qemu-devel] [PATCH 11/29] memory: include DIRTY_MEMORY_MIGRATION in the dirty log mask

[Paolo Bonzini <pbonzini@redhat.com>]

The separate handling of DIRTY_MEMORY_MIGRATION, which does not
call log_start/log_stop callbacks when it changes in a region's
dirty logging mask, has caused several bugs.

One recent example is commit 4cc856f (kvm-all: Sync dirty-bitmap from
kvm before kvm destroy the corresponding dirty_bitmap, 2015-04-02).
Another performance problem is that KVM keeps tracking dirty pages
after a failed live migration, which causes bad performance due to
disallowing huge page mapping.

This patch removes the root cause of the problem by reporting
DIRTY_MEMORY_MIGRATION changes via log_start and log_stop.
Note that we now have to rebuild the FlatView when global dirty
logging is enabled or disabled; this ensures that log_start and
log_stop callbacks are invoked.

This will also be used to make the setting of bitmaps conditional.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 memory.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/memory.c b/memory.c
index 1966347..174cd15 100644
--- a/memory.c
+++ b/memory.c
@@ -537,7 +537,7 @@ static void render_memory_region(FlatView *view,
     remain = clip.size;
 
     fr.mr = mr;
-    fr.dirty_log_mask = mr->dirty_log_mask;
+    fr.dirty_log_mask = memory_region_get_dirty_log_mask(mr);
     fr.romd_mode = mr->romd_mode;
     fr.readonly = readonly;
 
@@ -1329,7 +1329,11 @@ bool memory_region_is_skip_dump(MemoryRegion *mr)
 
 uint8_t memory_region_get_dirty_log_mask(MemoryRegion *mr)
 {
-    return mr->dirty_log_mask;
+    uint8_t mask = mr->dirty_log_mask;
+    if (global_dirty_log) {
+        mask |= (1 << DIRTY_MEMORY_MIGRATION);
+    }
+    return mask;
 }
 
 bool memory_region_is_logging(MemoryRegion *mr, uint8_t client)
@@ -1892,10 +1896,20 @@ void memory_global_dirty_log_start(void)
 {
     global_dirty_log = true;
     MEMORY_LISTENER_CALL_GLOBAL(log_global_start, Forward);
+
+    /* Refresh DIRTY_LOG_MIGRATION bit.  */
+    memory_region_transaction_begin();
+    memory_region_update_pending = true;
+    memory_region_transaction_commit();
 }
 
 void memory_global_dirty_log_stop(void)
 {
+    /* Refresh DIRTY_LOG_MIGRATION bit.  */
+    memory_region_transaction_begin();
+    memory_region_update_pending = true;
+    memory_region_transaction_commit();
+
     global_dirty_log = false;
     MEMORY_LISTENER_CALL_GLOBAL(log_global_stop, Reverse);
 }
-- 
1.8.3.1