1 files changed, 52 insertions, 0 deletions
diff --git a/exec.c b/exec.c
index 21926dc9c7..893636176e 100644
--- a/exec.c
+++ b/exec.c
@@ -4115,4 +4115,56 @@ void mtree_print_dispatch(AddressSpaceDispatch *d, MemoryRegion *root)
     }
 }
 
+/*
+ * If positive, discarding RAM is disabled. If negative, discarding RAM is
+ * required to work and cannot be disabled.
+ */
+static int ram_block_discard_disabled;
+
+int ram_block_discard_disable(bool state)
+{
+    int old;
+
+    if (!state) {
+        atomic_dec(&ram_block_discard_disabled);
+        return 0;
+    }
+
+    do {
+        old = atomic_read(&ram_block_discard_disabled);
+        if (old < 0) {
+            return -EBUSY;
+        }
+    } while (atomic_cmpxchg(&ram_block_discard_disabled, old, old + 1) != old);
+    return 0;
+}
+
+int ram_block_discard_require(bool state)
+{
+    int old;
+
+    if (!state) {
+        atomic_inc(&ram_block_discard_disabled);
+        return 0;
+    }
+
+    do {
+        old = atomic_read(&ram_block_discard_disabled);
+        if (old > 0) {
+            return -EBUSY;
+        }
+    } while (atomic_cmpxchg(&ram_block_discard_disabled, old, old - 1) != old);
+    return 0;
+}
+
+bool ram_block_discard_is_disabled(void)
+{
+    return atomic_read(&ram_block_discard_disabled) > 0;
+}
+
+bool ram_block_discard_is_required(void)
+{
+    return atomic_read(&ram_block_discard_disabled) < 0;
+}
+
 #endif