1 files changed, 47 insertions, 0 deletions
diff --git a/migration/ram.c b/migration/ram.c
index 0747873ca9..32c0dbb98a 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3182,6 +3182,53 @@ static void ram_state_resume_prepare(RAMState *rs, QEMUFile *out)
 }
 
 /*
+ * This function clears bits of the free pages reported by the caller from the
+ * migration dirty bitmap. @addr is the host address corresponding to the
+ * start of the continuous guest free pages, and @len is the total bytes of
+ * those pages.
+ */
+void qemu_guest_free_page_hint(void *addr, size_t len)
+{
+    RAMBlock *block;
+    ram_addr_t offset;
+    size_t used_len, start, npages;
+    MigrationState *s = migrate_get_current();
+
+    /* This function is currently expected to be used during live migration */
+    if (!migration_is_setup_or_active(s->state)) {
+        return;
+    }
+
+    for (; len > 0; len -= used_len, addr += used_len) {
+        block = qemu_ram_block_from_host(addr, false, &offset);
+        if (unlikely(!block || offset >= block->used_length)) {
+            /*
+             * The implementation might not support RAMBlock resize during
+             * live migration, but it could happen in theory with future
+             * updates. So we add a check here to capture that case.
+             */
+            error_report_once("%s unexpected error", __func__);
+            return;
+        }
+
+        if (len <= block->used_length - offset) {
+            used_len = len;
+        } else {
+            used_len = block->used_length - offset;
+        }
+
+        start = offset >> TARGET_PAGE_BITS;
+        npages = used_len >> TARGET_PAGE_BITS;
+
+        qemu_mutex_lock(&ram_state->bitmap_mutex);
+        ram_state->migration_dirty_pages -=
+                      bitmap_count_one_with_offset(block->bmap, start, npages);
+        bitmap_clear(block->bmap, start, npages);
+        qemu_mutex_unlock(&ram_state->bitmap_mutex);
+    }
+}
+
+/*
  * Each of ram_save_setup, ram_save_iterate and ram_save_complete has
  * long-running RCU critical section.  When rcu-reclaims in the code
  * start to become numerous it will be necessary to reduce the