memory: the only dirty memory flag for users is DIRTY_MEMORY_VGA

DIRTY_MEMORY_MIGRATION is triggered by memory_global_dirty_log_start
and memory_global_dirty_log_stop, so it cannot be used with
memory_region_set_log.

Specify this in the documentation and assert it.
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

include/exec/memory.h

@@ -647,8 +647,7 @@ void memory_region_ram_resize(MemoryRegion *mr, ram_addr_t newsize,
  *
  * @mr: the memory region being updated.
  * @log: whether dirty logging is to be enabled or disabled.
- * @client: the user of the logging information; %DIRTY_MEMORY_MIGRATION or
- *          %DIRTY_MEMORY_VGA.
+ * @client: the user of the logging information; %DIRTY_MEMORY_VGA only.
  */
 void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client);
 

memory.c

@@ -1425,6 +1425,7 @@ void memory_region_set_log(MemoryRegion *mr, bool log, unsigned client)
 {
     uint8_t mask = 1 << client;
 
+    assert(client == DIRTY_MEMORY_VGA);
     memory_region_transaction_begin();
     mr->dirty_log_mask = (mr->dirty_log_mask & ~mask) | (log * mask);
     memory_region_update_pending |= mr->enabled;