[Patch v2 3/6] migration/postcopy: count target page number to decide the place_needed

[Wei Yang]

In postcopy, it requires to place whole host page instead of target
page.

Currently, it relies on the page offset to decide whether this is the
last target page. We also can count the target page number during the
iteration. When the number of target page equals
(host page size / target page size), this means it is the last target
page in the host page.

This is a preparation for non-ordered target page transmission.

Signed-off-by: Wei Yang <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
---
 migration/ram.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/migration/ram.c b/migration/ram.c
index f59e3fe197..5c05376d8d 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -4017,6 +4017,7 @@ static int ram_load_postcopy(QEMUFile *f)
     void *postcopy_host_page = mis->postcopy_tmp_page;
     void *last_host = NULL;
     bool all_zero = false;
+    int target_pages = 0;
 
     while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
         ram_addr_t addr;
@@ -4051,6 +4052,7 @@ static int ram_load_postcopy(QEMUFile *f)
                 ret = -EINVAL;
                 break;
             }
+            target_pages++;
             matches_target_page_size = block->page_size == TARGET_PAGE_SIZE;
             /*
              * Postcopy requires that we place whole host pages atomically;
@@ -4082,8 +4084,10 @@ static int ram_load_postcopy(QEMUFile *f)
              * If it's the last part of a host page then we place the host
              * page
              */
-            place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) &
-                                     (block->page_size - 1)) == 0;
+            if (target_pages == (block->page_size / TARGET_PAGE_SIZE)) {
+                place_needed = true;
+                target_pages = 0;
+            }
             place_source = postcopy_host_page;
         }
         last_host = host;
-- 
2.17.1