[Qemu-devel] [PATCH 1/8] memory: Add global-locking property to memory regions

[Paolo Bonzini <pbonzini@redhat.com>]

From: Jan Kiszka <jan.kiszka@siemens.com>

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/exec/memory.h | 26 ++++++++++++++++++++++++++
 memory.c              | 11 +++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 06ffa1d..0ee2079 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -158,6 +158,7 @@ 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;
@@ -778,6 +779,31 @@ 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, access to this memory regions 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.
  *
diff --git a/memory.c b/memory.c
index ee3f2a8..cc798e1 100644
--- a/memory.c
+++ b/memory.c
@@ -953,6 +953,7 @@ static void memory_region_initfn(Object *obj)
     mr->ops = &unassigned_mem_ops;
     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);
@@ -1549,6 +1550,16 @@ 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,
-- 
2.3.0