[v5,6/6] hostmem: Handle remapping of RAM

Commit Message

“William Roche Jan. 10, 2025, 9:14 p.m. UTC

From: David Hildenbrand <[e-mail]>

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

Merging and dump settings are handled by the remap notification
in addition to memory policy and preallocation.

Signed-off-by: David Hildenbrand <[e-mail]>
Signed-off-by: William Roche <[e-mail]>
---
 backends/hostmem.c       | 34 ++++++++++++++++++++++++++++++++++
 include/system/hostmem.h |  1 +
 system/physmem.c         |  4 ----
 3 files changed, 35 insertions(+), 4 deletions(-)

Patch

diff --git a/backends/hostmem.c b/backends/hostmem.c
index 46d80f98b4..4589467c77 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/system/hostmem.h b/include/system/hostmem.h
index 5c21ca55c0..170849e8a4 100644
--- a/include/system/hostmem.h
+++ b/include/system/hostmem.h
@@ -83,6 +83,7 @@  struct HostMemoryBackend {
     HostMemPolicy policy;
 
     MemoryRegion mr;
+    RAMBlockNotifier ram_notifier;
 };
 
 bool host_memory_backend_mr_inited(HostMemoryBackend *backend);
diff --git a/system/physmem.c b/system/physmem.c
index b8cd49a110..306e71861d 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2205,7 +2205,6 @@  void qemu_ram_remap(ram_addr_t addr)
 {
     RAMBlock *block;
     ram_addr_t offset;
-    void *vaddr;
     size_t page_size;
 
     RAMBLOCK_FOREACH(block) {
@@ -2215,7 +2214,6 @@  void qemu_ram_remap(ram_addr_t addr)
             page_size = qemu_ram_pagesize(block);
             offset = QEMU_ALIGN_DOWN(offset, page_size);
 
-            vaddr = ramblock_ptr(block, offset);
             if (block->flags & RAM_PREALLOC) {
                 ;
             } else if (xen_enabled()) {
@@ -2236,8 +2234,6 @@  void qemu_ram_remap(ram_addr_t addr)
                     }
                     qemu_ram_remap_mmap(block, offset, page_size);
                 }
-                memory_try_enable_merging(vaddr, page_size);
-                qemu_ram_setup_dump(vaddr, page_size);
                 ram_block_notify_remap(block->host, offset, page_size);
             }