memory: Add global-locking property to memory regions

This introduces the memory region property "global_locking". It is true
by default. By setting it to false, a device model can request BQL-free
dispatching of region accesses to its r/w handlers. The actual BQL
break-up will be provided in a separate patch.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Frederic Konrad <fred.konrad@greensocs.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1434646046-27150-4-git-send-email-pbonzini@redhat.com>

include/exec/memory.h

@@ -180,6 +180,7 @@ struct MemoryRegion {
     bool rom_device;
     bool warning_printed; /* For reservations */
     bool flush_coalesced_mmio;
+    bool global_locking;
     MemoryRegion *alias;
     hwaddr alias_offset;
     int32_t priority;
@@ -824,6 +825,31 @@ void memory_region_set_flush_coalesced(MemoryRegion *mr);
  */
 void memory_region_clear_flush_coalesced(MemoryRegion *mr);
 
+/**
+ * memory_region_set_global_locking: Declares the access processing requires
+ *                                   QEMU's global lock.
+ *
+ * When this is invoked, accesses to the memory region will be processed while
+ * holding the global lock of QEMU. This is the default behavior of memory
+ * regions.
+ *
+ * @mr: the memory region to be updated.
+ */
+void memory_region_set_global_locking(MemoryRegion *mr);
+
+/**
+ * memory_region_clear_global_locking: Declares that access processing does
+ *                                     not depend on the QEMU global lock.
+ *
+ * By clearing this property, accesses to the memory region will be processed
+ * outside of QEMU's global lock (unless the lock is held on when issuing the
+ * access request). In this case, the device model implementing the access
+ * handlers is responsible for synchronization of concurrency.
+ *
+ * @mr: the memory region to be updated.
+ */
+void memory_region_clear_global_locking(MemoryRegion *mr);
+
 /**
  * memory_region_add_eventfd: Request an eventfd to be triggered when a word
  *                            is written to a location.

memory.c

@@ -1012,6 +1012,7 @@ static void memory_region_initfn(Object *obj)
     mr->ram_addr = RAM_ADDR_INVALID;
     mr->enabled = true;
     mr->romd_mode = true;
+    mr->global_locking = true;
     mr->destructor = memory_region_destructor_none;
     QTAILQ_INIT(&mr->subregions);
     QTAILQ_INIT(&mr->coalesced);
@@ -1646,6 +1647,16 @@ void memory_region_clear_flush_coalesced(MemoryRegion *mr)
     }
 }
 
+void memory_region_set_global_locking(MemoryRegion *mr)
+{
+    mr->global_locking = true;
+}
+
+void memory_region_clear_global_locking(MemoryRegion *mr)
+{
+    mr->global_locking = false;
+}
+
 void memory_region_add_eventfd(MemoryRegion *mr,
                                hwaddr addr,
                                unsigned size,