1 files changed, 76 insertions, 19 deletions

diff --git a/migration/ram.c b/migration/ram.c
index f4cd9038f4..4d7b50ef79 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -481,6 +481,11 @@ struct PageSearchStatus {
      * postcopy pages via postcopy preempt channel.
      */
     bool         postcopy_target_channel;
+    /* Whether we're sending a host page */
+    bool          host_page_sending;
+    /* The start/end of current host page.  Only valid if host_page_sending==true */
+    unsigned long host_page_start;
+    unsigned long host_page_end;
 };
 typedef struct PageSearchStatus PageSearchStatus;
 
@@ -858,26 +863,38 @@ static int save_xbzrle_page(RAMState *rs, uint8_t **current_data,
 }
 
 /**
- * migration_bitmap_find_dirty: find the next dirty page from start
+ * pss_find_next_dirty: find the next dirty page of current ramblock
  *
- * Returns the page offset within memory region of the start of a dirty page
+ * This function updates pss->page to point to the next dirty page index
+ * within the ramblock to migrate, or the end of ramblock when nothing
+ * found.  Note that when pss->host_page_sending==true it means we're
+ * during sending a host page, so we won't look for dirty page that is
+ * outside the host page boundary.
  *
- * @rs: current RAM state
- * @rb: RAMBlock where to search for dirty pages
- * @start: page where we start the search
+ * @pss: the current page search status
  */
-static inline
-unsigned long migration_bitmap_find_dirty(RAMState *rs, RAMBlock *rb,
-                                          unsigned long start)
+static void pss_find_next_dirty(PageSearchStatus *pss)
 {
+    RAMBlock *rb = pss->block;
     unsigned long size = rb->used_length >> TARGET_PAGE_BITS;
     unsigned long *bitmap = rb->bmap;
 
     if (ramblock_is_ignored(rb)) {
-        return size;
+        /* Points directly to the end, so we know no dirty page */
+        pss->page = size;
+        return;
+    }
+
+    /*
+     * If during sending a host page, only look for dirty pages within the
+     * current host page being send.
+     */
+    if (pss->host_page_sending) {
+        assert(pss->host_page_end);
+        size = MIN(size, pss->host_page_end);
     }
 
-    return find_next_bit(bitmap, size, start);
+    pss->page = find_next_bit(bitmap, size, pss->page);
 }
 
 static void migration_clear_memory_region_dirty_bitmap(RAMBlock *rb,
@@ -1563,7 +1580,9 @@ static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss, bool *again)
     pss->postcopy_requested = false;
     pss->postcopy_target_channel = RAM_CHANNEL_PRECOPY;
 
-    pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
+    /* Update pss->page for the next dirty bit in ramblock */
+    pss_find_next_dirty(pss);
+
     if (pss->complete_round && pss->block == rs->last_seen_block &&
         pss->page >= rs->last_page) {
         /*
@@ -2452,6 +2471,44 @@ static void postcopy_preempt_reset_channel(RAMState *rs)
     }
 }
 
+/* Should be called before sending a host page */
+static void pss_host_page_prepare(PageSearchStatus *pss)
+{
+    /* How many guest pages are there in one host page? */
+    size_t guest_pfns = qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
+
+    pss->host_page_sending = true;
+    pss->host_page_start = ROUND_DOWN(pss->page, guest_pfns);
+    pss->host_page_end = ROUND_UP(pss->page + 1, guest_pfns);
+}
+
+/*
+ * Whether the page pointed by PSS is within the host page being sent.
+ * Must be called after a previous pss_host_page_prepare().
+ */
+static bool pss_within_range(PageSearchStatus *pss)
+{
+    ram_addr_t ram_addr;
+
+    assert(pss->host_page_sending);
+
+    /* Over host-page boundary? */
+    if (pss->page >= pss->host_page_end) {
+        return false;
+    }
+
+    ram_addr = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS;
+
+    return offset_in_ramblock(pss->block, ram_addr);
+}
+
+static void pss_host_page_finish(PageSearchStatus *pss)
+{
+    pss->host_page_sending = false;
+    /* This is not needed, but just to reset it */
+    pss->host_page_start = pss->host_page_end = 0;
+}
+
 /**
  * ram_save_host_page: save a whole host page
  *
@@ -2479,8 +2536,6 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss)
     int tmppages, pages = 0;
     size_t pagesize_bits =
         qemu_ram_pagesize(pss->block) >> TARGET_PAGE_BITS;
-    unsigned long hostpage_boundary =
-        QEMU_ALIGN_UP(pss->page + 1, pagesize_bits);
     unsigned long start_page = pss->page;
     int res;
 
@@ -2493,6 +2548,9 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss)
         postcopy_preempt_choose_channel(rs, pss);
     }
 
+    /* Update host page boundary information */
+    pss_host_page_prepare(pss);
+
     do {
         if (postcopy_needs_preempt(rs, pss)) {
             postcopy_do_preempt(rs, pss);
@@ -2530,15 +2588,14 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss)
         }
 
         if (tmppages < 0) {
+            pss_host_page_finish(pss);
             return tmppages;
         }
 
-        pss->page = migration_bitmap_find_dirty(rs, pss->block, pss->page);
-    } while ((pss->page < hostpage_boundary) &&
-             offset_in_ramblock(pss->block,
-                                ((ram_addr_t)pss->page) << TARGET_PAGE_BITS));
-    /* The offset we leave with is the min boundary of host page and block */
-    pss->page = MIN(pss->page, hostpage_boundary);
+        pss_find_next_dirty(pss);
+    } while (pss_within_range(pss));
+
+    pss_host_page_finish(pss);
 
     /*
      * When with postcopy preempt mode, flush the data as soon as possible for