memory: add API for observing updates to the physical memory map

Add an API that allows a client to observe changes in the global
memory map:
 - region added (possibly with logging enabled)
 - region removed (possibly with logging enabled)
 - logging started on a region
 - logging stopped on a region
 - global logging started
 - global logging removed

This API will eventually replace cpu_register_physical_memory_client().

Signed-off-by: Avi Kivity <avi@redhat.com>

exec.c

@@ -1762,6 +1762,11 @@ static int cpu_notify_sync_dirty_bitmap(target_phys_addr_t start,
 static int cpu_notify_migration_log(int enable)
 {
     CPUPhysMemoryClient *client;
+    if (enable) {
+        memory_global_dirty_log_start();
+    } else {
+        memory_global_dirty_log_stop();
+    }
     QLIST_FOREACH(client, &memory_client_list, list) {
         int r = client->migration_log(client, enable);
         if (r < 0)

memory.c

@@ -23,6 +23,10 @@
 
 unsigned memory_region_transaction_depth = 0;
 static bool memory_region_update_pending = false;
+static bool global_dirty_log = false;
+
+static QLIST_HEAD(, MemoryListener) memory_listeners
+    = QLIST_HEAD_INITIALIZER(memory_listeners);
 
 typedef struct AddrRange AddrRange;
 
@@ -697,6 +701,32 @@ static void address_space_update_ioeventfds(AddressSpace *as)
     as->ioeventfd_nb = ioeventfd_nb;
 }
 
+typedef void ListenerCallback(MemoryListener *listener,
+                              MemoryRegionSection *mrs);
+
+/* Want "void (&MemoryListener::*callback)(const MemoryRegionSection& s)" */
+static void memory_listener_update_region(FlatRange *fr, AddressSpace *as,
+                                          size_t callback_offset)
+{
+    MemoryRegionSection section = {
+        .mr = fr->mr,
+        .address_space = as->root,
+        .offset_within_region = fr->offset_in_region,
+        .size = int128_get64(fr->addr.size),
+        .offset_within_address_space = int128_get64(fr->addr.start),
+    };
+    MemoryListener *listener;
+
+    QLIST_FOREACH(listener, &memory_listeners, link) {
+        ListenerCallback *callback
+            = *(ListenerCallback **)((void *)listener + callback_offset);
+        callback(listener, &section);
+    }
+}
+
+#define MEMORY_LISTENER_UPDATE_REGION(fr, as, callback) \
+    memory_listener_update_region(fr, as, offsetof(MemoryListener, callback))
+
 static void address_space_update_topology_pass(AddressSpace *as,
                                                FlatView old_view,
                                                FlatView new_view,
@@ -729,6 +759,7 @@ static void address_space_update_topology_pass(AddressSpace *as,
             /* In old, but (not in new, or in new but attributes changed). */
 
             if (!adding) {
+                MEMORY_LISTENER_UPDATE_REGION(frold, as, region_del);
                 as->ops->range_del(as, frold);
             }
 
@@ -738,9 +769,11 @@ static void address_space_update_topology_pass(AddressSpace *as,
 
             if (adding) {
                 if (frold->dirty_log_mask && !frnew->dirty_log_mask) {
+                    MEMORY_LISTENER_UPDATE_REGION(frold, as, log_stop);
                     as->ops->log_stop(as, frnew);
                 } else if (frnew->dirty_log_mask && !frold->dirty_log_mask) {
                     as->ops->log_start(as, frnew);
+                    MEMORY_LISTENER_UPDATE_REGION(frold, as, log_start);
                 }
             }
 
@@ -751,6 +784,7 @@ static void address_space_update_topology_pass(AddressSpace *as,
 
             if (adding) {
                 as->ops->range_add(as, frnew);
+                MEMORY_LISTENER_UPDATE_REGION(frold, as, region_add);
             }
 
             ++inew;
@@ -1130,6 +1164,7 @@ void memory_region_sync_dirty_bitmap(MemoryRegion *mr)
 
     FOR_EACH_FLAT_RANGE(fr, &address_space_memory.current_map) {
         if (fr->mr == mr) {
+            MEMORY_LISTENER_UPDATE_REGION(fr, &address_space_memory, log_sync);
             cpu_physical_sync_dirty_bitmap(int128_get64(fr->addr.start),
                                            int128_get64(addrrange_end(fr->addr)));
         }
@@ -1449,7 +1484,65 @@ MemoryRegionSection memory_region_find(MemoryRegion *address_space,
 
 void memory_global_sync_dirty_bitmap(MemoryRegion *address_space)
 {
+    AddressSpace *as = memory_region_to_address_space(address_space);
+    FlatRange *fr;
+
     cpu_physical_sync_dirty_bitmap(0, TARGET_PHYS_ADDR_MAX);
+    FOR_EACH_FLAT_RANGE(fr, &as->current_map) {
+        MEMORY_LISTENER_UPDATE_REGION(fr, as, log_sync);
+    }
+}
+
+void memory_global_dirty_log_start(void)
+{
+    MemoryListener *listener;
+
+    global_dirty_log = true;
+    QLIST_FOREACH(listener, &memory_listeners, link) {
+        listener->log_global_start(listener);
+    }
+}
+
+void memory_global_dirty_log_stop(void)
+{
+    MemoryListener *listener;
+
+    global_dirty_log = false;
+    QLIST_FOREACH(listener, &memory_listeners, link) {
+        listener->log_global_stop(listener);
+    }
+}
+
+static void listener_add_address_space(MemoryListener *listener,
+                                       AddressSpace *as)
+{
+    FlatRange *fr;
+
+    if (global_dirty_log) {
+        listener->log_global_start(listener);
+    }
+    FOR_EACH_FLAT_RANGE(fr, &as->current_map) {
+        MemoryRegionSection section = {
+            .mr = fr->mr,
+            .address_space = as->root,
+            .offset_within_region = fr->offset_in_region,
+            .size = int128_get64(fr->addr.size),
+            .offset_within_address_space = int128_get64(fr->addr.start),
+        };
+        listener->region_add(listener, &section);
+    }
+}
+
+void memory_listener_register(MemoryListener *listener)
+{
+    QLIST_INSERT_HEAD(&memory_listeners, listener, link);
+    listener_add_address_space(listener, &address_space_memory);
+    listener_add_address_space(listener, &address_space_io);
+}
+
+void memory_listener_unregister(MemoryListener *listener)
+{
+    QLIST_REMOVE(listener, link);
 }
 
 void set_system_memory_map(MemoryRegion *mr)

memory.h

@@ -154,6 +154,7 @@ typedef struct MemoryRegionSection MemoryRegionSection;
  * MemoryRegionSection: describes a fragment of a #MemoryRegion
  *
  * @mr: the region, or %NULL if empty
+ * @address_space: the address space the region is mapped in
  * @offset_within_region: the beginning of the section, relative to @mr's start
  * @size: the size of the section; will not exceed @mr's boundaries
  * @offset_within_address_space: the address of the first byte of the section
@@ -161,11 +162,31 @@ typedef struct MemoryRegionSection MemoryRegionSection;
  */
 struct MemoryRegionSection {
     MemoryRegion *mr;
+    MemoryRegion *address_space;
     target_phys_addr_t offset_within_region;
     uint64_t size;
     target_phys_addr_t offset_within_address_space;
 };
 
+typedef struct MemoryListener MemoryListener;
+
+/**
+ * MemoryListener: callbacks structure for updates to the physical memory map
+ *
+ * Allows a component to adjust to changes in the guest-visible memory map.
+ * Use with memory_listener_register() and memory_listener_unregister().
+ */
+struct MemoryListener {
+    void (*region_add)(MemoryListener *listener, MemoryRegionSection *section);
+    void (*region_del)(MemoryListener *listener, MemoryRegionSection *section);
+    void (*log_start)(MemoryListener *listener, MemoryRegionSection *section);
+    void (*log_stop)(MemoryListener *listener, MemoryRegionSection *section);
+    void (*log_sync)(MemoryListener *listener, MemoryRegionSection *section);
+    void (*log_global_start)(MemoryListener *listener);
+    void (*log_global_stop)(MemoryListener *listener);
+    QLIST_ENTRY(MemoryListener) link;
+};
+
 /**
  * memory_region_init: Initialize a memory region
  *
@@ -631,6 +652,32 @@ void memory_region_transaction_begin(void);
  */
 void memory_region_transaction_commit(void);
 
+/**
+ * memory_listener_register: register callbacks to be called when memory
+ *                           sections are mapped or unmapped into an address
+ *                           space
+ *
+ * @listener: an object containing the callbacks to be called
+ */
+void memory_listener_register(MemoryListener *listener);
+
+/**
+ * memory_listener_unregister: undo the effect of memory_listener_register()
+ *
+ * @listener: an object containing the callbacks to be removed
+ */
+void memory_listener_unregister(MemoryListener *listener);
+
+/**
+ * memory_global_dirty_log_start: begin dirty logging for all regions
+ */
+void memory_global_dirty_log_start(void);
+
+/**
+ * memory_global_dirty_log_stop: begin dirty logging for all regions
+ */
+void memory_global_dirty_log_stop(void);
+
 void mtree_info(fprintf_function mon_printf, void *f);
 
 #endif