[Qemu-devel] [PATCH 06/15] memory: use refcnt to manage MemoryRegion

[Liu Ping Fan <qemulist@gmail.com>]

From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>

Using refcnt for mr, so we can separate mr's life cycle management
from refered object.
  When mr->ref 0->1, inc the refered object.
  When mr->ref 1->0, dec the refered object.

The refered object can be DeviceStae, another mr, or other opaque.

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
 memory.c |   18 ++++++++++++++++++
 memory.h |    5 +++++
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/memory.c b/memory.c
index 80c7529..5dc8b59 100644
--- a/memory.c
+++ b/memory.c
@@ -811,6 +811,7 @@ void memory_region_init(MemoryRegion *mr,
     if (size == UINT64_MAX) {
         mr->size = int128_2_64();
     }
+    atomic_set(&mr->ref, 0);
     mr->life_ops = &nops;
     mr->addr = 0;
     mr->subpage = false;
@@ -1090,6 +1091,23 @@ static const MemoryRegionOps reservation_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
+void memory_region_get(MemoryRegion *mr)
+{
+    if (atomic_add_and_return(1, &mr->ref) == 1) {
+        mr->life_ops->get(mr);
+    }
+}
+
+void memory_region_put(MemoryRegion *mr)
+{
+    assert(atomic_read(&mr->ref) > 0);
+
+    if (atomic_dec_and_test(&mr->ref)) {
+        /* to fix, using call_rcu( ,release) */
+        mr->life_ops->put(mr);
+    }
+}
+
 void memory_region_init_reservation(MemoryRegion *mr,
                                     const char *name,
                                     uint64_t size)
diff --git a/memory.h b/memory.h
index 8fb543b..740f018 100644
--- a/memory.h
+++ b/memory.h
@@ -18,6 +18,7 @@
 
 #include <stdint.h>
 #include <stdbool.h>
+#include "qemu/atomic.h"
 #include "qemu-common.h"
 #include "cpu-common.h"
 #include "targphys.h"
@@ -26,6 +27,7 @@
 #include "ioport.h"
 #include "int128.h"
 #include "qemu-thread.h"
+#include "qemu/reclaimer.h"
 
 typedef struct MemoryRegionOps MemoryRegionOps;
 typedef struct MemoryRegionLifeOps MemoryRegionLifeOps;
@@ -126,6 +128,7 @@ typedef struct MemoryRegionIoeventfd MemoryRegionIoeventfd;
 struct MemoryRegion {
     /* All fields are private - violators will be prosecuted */
     const MemoryRegionOps *ops;
+    Atomic ref;
     MemoryRegionLifeOps *life_ops;
     void *opaque;
     MemoryRegion *parent;
@@ -766,6 +769,8 @@ void memory_global_dirty_log_stop(void);
 
 void mtree_info(fprintf_function mon_printf, void *f);
 
+void memory_region_get(MemoryRegion *mr);
+void memory_region_put(MemoryRegion *mr);
 #endif
 
 #endif
-- 
1.7.4.4