commit b87eaa9b8237f4d97950ca0f78309407212cfdc5
author Peter Xu <peterx@redhat.com> Thu May 06 12:05:40 2021 -0400
committer Paolo Bonzini <pbonzini@redhat.com> Wed May 26 14:49:45 2021 +0200
tree aa5b94543d0a1f7cf71303eb94beeac3a6e8a216
parent 70cbae429ef3a7c36facd418da2c00e01ae51cb7

memory: Introduce log_sync_global() to memory listener

Some of the memory listener may want to do log synchronization without
being able to specify a range of memory to sync but always globally.
Such a memory listener should provide this new method instead of the
log_sync() method.

Obviously we can also achieve similar thing when we put the global
sync logic into a log_sync() handler. However that's not efficient
enough because otherwise memory_global_dirty_log_sync() may do the
global sync N times, where N is the number of flat ranges in the
address space.

Make this new method be exclusive to log_sync().

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210506160549.130416-2-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/exec/memory.h

diff --git a/include/exec/memory.h b/include/exec/memory.h
index c8b9088..e38b7e3 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -617,6 +617,18 @@
     void (*log_sync)(MemoryListener *listener, MemoryRegionSection *section);
 
     /**
+     * @log_sync_global:
+     *
+     * This is the global version of @log_sync when the listener does
+     * not have a way to synchronize the log with finer granularity.
+     * When the listener registers with @log_sync_global defined, then
+     * its @log_sync must be NULL.  Vice versa.
+     *
+     * @listener: The #MemoryListener.
+     */
+    void (*log_sync_global)(MemoryListener *listener);
+
+    /**
      * @log_clear:
      *
      * Called before reading the dirty memory bitmap for a

softmmu/memory.c

diff --git a/softmmu/memory.c b/softmmu/memory.c
index 3bb533c..c19b0be 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2055,6 +2055,10 @@
                                         memory_region_get_dirty_log_mask(mr));
 }
 
+/*
+ * If memory region `mr' is NULL, do global sync.  Otherwise, sync
+ * dirty bitmap for the specified memory region.
+ */
 static void memory_region_sync_dirty_bitmap(MemoryRegion *mr)
 {
     MemoryListener *listener;
@@ -2068,18 +2072,24 @@
      * address space once.
      */
     QTAILQ_FOREACH(listener, &memory_listeners, link) {
-        if (!listener->log_sync) {
-            continue;
-        }
-        as = listener->address_space;
-        view = address_space_get_flatview(as);
-        FOR_EACH_FLAT_RANGE(fr, view) {
-            if (fr->dirty_log_mask && (!mr || fr->mr == mr)) {
-                MemoryRegionSection mrs = section_from_flat_range(fr, view);
-                listener->log_sync(listener, &mrs);
+        if (listener->log_sync) {
+            as = listener->address_space;
+            view = address_space_get_flatview(as);
+            FOR_EACH_FLAT_RANGE(fr, view) {
+                if (fr->dirty_log_mask && (!mr || fr->mr == mr)) {
+                    MemoryRegionSection mrs = section_from_flat_range(fr, view);
+                    listener->log_sync(listener, &mrs);
+                }
             }
+            flatview_unref(view);
+        } else if (listener->log_sync_global) {
+            /*
+             * No matter whether MR is specified, what we can do here
+             * is to do a global sync, because we are not capable to
+             * sync in a finer granularity.
+             */
+            listener->log_sync_global(listener);
         }
-        flatview_unref(view);
     }
 }
 
@@ -2767,6 +2777,9 @@
 {
     MemoryListener *other = NULL;
 
+    /* Only one of them can be defined for a listener */
+    assert(!(listener->log_sync && listener->log_sync_global));
+
     listener->address_space = as;
     if (QTAILQ_EMPTY(&memory_listeners)
         || listener->priority >= QTAILQ_LAST(&memory_listeners)->priority) {