ramblock-notifier: new

This adds a notify interface of ram block additions and removals.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/include/exec/ramlist.h b/include/exec/ramlist.h
new file mode 100644
index 0000000000..c59880de82
--- /dev/null
+++ b/include/exec/ramlist.h
@@ -0,0 +1,72 @@
+#ifndef RAMLIST_H
+#define RAMLIST_H
+
+#include "qemu/queue.h"
+#include "qemu/thread.h"
+#include "qemu/rcu.h"
+
+typedef struct RAMBlockNotifier RAMBlockNotifier;
+
+#define DIRTY_MEMORY_VGA       0
+#define DIRTY_MEMORY_CODE      1
+#define DIRTY_MEMORY_MIGRATION 2
+#define DIRTY_MEMORY_NUM       3        /* num of dirty bits */
+
+/* The dirty memory bitmap is split into fixed-size blocks to allow growth
+ * under RCU.  The bitmap for a block can be accessed as follows:
+ *
+ *   rcu_read_lock();
+ *
+ *   DirtyMemoryBlocks *blocks =
+ *       atomic_rcu_read(&ram_list.dirty_memory[DIRTY_MEMORY_MIGRATION]);
+ *
+ *   ram_addr_t idx = (addr >> TARGET_PAGE_BITS) / DIRTY_MEMORY_BLOCK_SIZE;
+ *   unsigned long *block = blocks.blocks[idx];
+ *   ...access block bitmap...
+ *
+ *   rcu_read_unlock();
+ *
+ * Remember to check for the end of the block when accessing a range of
+ * addresses.  Move on to the next block if you reach the end.
+ *
+ * Organization into blocks allows dirty memory to grow (but not shrink) under
+ * RCU.  When adding new RAMBlocks requires the dirty memory to grow, a new
+ * DirtyMemoryBlocks array is allocated with pointers to existing blocks kept
+ * the same.  Other threads can safely access existing blocks while dirty
+ * memory is being grown.  When no threads are using the old DirtyMemoryBlocks
+ * anymore it is freed by RCU (but the underlying blocks stay because they are
+ * pointed to from the new DirtyMemoryBlocks).
+ */
+#define DIRTY_MEMORY_BLOCK_SIZE ((ram_addr_t)256 * 1024 * 8)
+typedef struct {
+    struct rcu_head rcu;
+    unsigned long *blocks[];
+} DirtyMemoryBlocks;
+
+typedef struct RAMList {
+    QemuMutex mutex;
+    RAMBlock *mru_block;
+    /* RCU-enabled, writes protected by the ramlist lock. */
+    QLIST_HEAD(, RAMBlock) blocks;
+    DirtyMemoryBlocks *dirty_memory[DIRTY_MEMORY_NUM];
+    uint32_t version;
+    QLIST_HEAD(, RAMBlockNotifier) ramblock_notifiers;
+} RAMList;
+extern RAMList ram_list;
+
+void qemu_mutex_lock_ramlist(void);
+void qemu_mutex_unlock_ramlist(void);
+
+struct RAMBlockNotifier {
+    void (*ram_block_added)(RAMBlockNotifier *n, void *host, size_t size);
+    void (*ram_block_removed)(RAMBlockNotifier *n, void *host, size_t size);
+    QLIST_ENTRY(RAMBlockNotifier) next;
+};
+
+void ram_block_notifier_add(RAMBlockNotifier *n);
+void ram_block_notifier_remove(RAMBlockNotifier *n);
+void ram_block_notify_add(void *host, size_t size);
+void ram_block_notify_remove(void *host, size_t size);
+
+
+#endif /* RAMLIST_H */