@@ -14,11 +14,13 @@
#ifndef MIGRATION_MISC_H
#define MIGRATION_MISC_H
+#include "exec/cpu-common.h"
#include "qemu/notify.h"
/* migration/ram.c */
void ram_mig_init(void);
+void qemu_guest_free_page_hint(void *addr, size_t len);
/* migration/block.c */
@@ -3131,6 +3131,53 @@ 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