From: David Hildenbrand <david@redhat.com>

Let's register a RAM block notifier and react on remap notifications.
Simply re-apply the settings. Exit if something goes wrong.

Note: qemu_ram_remap() will not remap when RAM_PREALLOC is set. Could be
that hostmem is still missing to update that flag ...

Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: William Roche <william.roche@oracle.com>
---
 backends/hostmem.c       | 34 ++++++++++++++++++++++++++++++++++
 include/sysemu/hostmem.h |  1 +
 2 files changed, 35 insertions(+)

diff --git a/backends/hostmem.c b/backends/hostmem.c
index bf85d716e5..863f6da11d 100644
--- a/backends/hostmem.c
+++ b/backends/hostmem.c
@@ -361,11 +361,37 @@ static void host_memory_backend_set_prealloc_threads(Object *obj, Visitor *v,
     backend->prealloc_threads = value;
 }
 
+static void host_memory_backend_ram_remapped(RAMBlockNotifier *n, void *host,
+                                             size_t offset, size_t size)
+{
+    HostMemoryBackend *backend = container_of(n, HostMemoryBackend,
+                                              ram_notifier);
+    Error *err = NULL;
+
+    if (!host_memory_backend_mr_inited(backend) ||
+        memory_region_get_ram_ptr(&backend->mr) != host) {
+        return;
+    }
+
+    host_memory_backend_apply_settings(backend, host + offset, size, &err);
+    if (err) {
+        /*
+         * If memory settings can't be successfully applied on remap,
+         * don't take the risk to continue without them.
+         */
+        error_report_err(err);
+        exit(1);
+    }
+}
+
 static void host_memory_backend_init(Object *obj)
 {
     HostMemoryBackend *backend = MEMORY_BACKEND(obj);
     MachineState *machine = MACHINE(qdev_get_machine());
 
+    backend->ram_notifier.ram_block_remapped = host_memory_backend_ram_remapped;
+    ram_block_notifier_add(&backend->ram_notifier);
+
     /* TODO: convert access to globals to compat properties */
     backend->merge = machine_mem_merge(machine);
     backend->dump = machine_dump_guest_core(machine);
@@ -379,6 +405,13 @@ static void host_memory_backend_post_init(Object *obj)
     object_apply_compat_props(obj);
 }
 
+static void host_memory_backend_finalize(Object *obj)
+{
+    HostMemoryBackend *backend = MEMORY_BACKEND(obj);
+
+    ram_block_notifier_remove(&backend->ram_notifier);
+}
+
 bool host_memory_backend_mr_inited(HostMemoryBackend *backend)
 {
     /*
@@ -595,6 +628,7 @@ static const TypeInfo host_memory_backend_info = {
     .instance_size = sizeof(HostMemoryBackend),
     .instance_init = host_memory_backend_init,
     .instance_post_init = host_memory_backend_post_init,
+    .instance_finalize = host_memory_backend_finalize,
     .interfaces = (InterfaceInfo[]) {
         { TYPE_USER_CREATABLE },
         { }
diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
index 67f45abe39..98309a9457 100644
--- a/include/sysemu/hostmem.h
+++ b/include/sysemu/hostmem.h
@@ -83,6 +83,7 @@ struct HostMemoryBackend {
     HostMemPolicy policy;
 
     MemoryRegion mr;
+    RAMBlockNotifier ram_notifier;
 };
 
 bool host_memory_backend_mr_inited(HostMemoryBackend *backend);
-- 
2.43.5