postcopy: Load huge pages in one go

The existing postcopy RAM load loop already ensures that it
glues together whole host-pages from the target page size chunks sent
over the wire.  Modify the definition of host page that it uses
to be the RAM block page size and thus be huge pages where appropriate.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20170224182844.32452-10-dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/ram.c

@@ -2390,7 +2390,7 @@ static int ram_load_postcopy(QEMUFile *f)
 {
     int flags = 0, ret = 0;
     bool place_needed = false;
-    bool matching_page_sizes = qemu_host_page_size == TARGET_PAGE_SIZE;
+    bool matching_page_sizes = false;
     MigrationIncomingState *mis = migration_incoming_get_current();
     /* Temporary page that is later 'placed' */
     void *postcopy_host_page = postcopy_get_tmp_page(mis);
@@ -2420,18 +2420,21 @@ static int ram_load_postcopy(QEMUFile *f)
                 ret = -EINVAL;
                 break;
             }
+            matching_page_sizes = block->page_size == TARGET_PAGE_SIZE;
             /*
-             * Postcopy requires that we place whole host pages atomically.
+             * Postcopy requires that we place whole host pages atomically;
+             * these may be huge pages for RAMBlocks that are backed by
+             * hugetlbfs.
              * To make it atomic, the data is read into a temporary page
              * that's moved into place later.
              * The migration protocol uses,  possibly smaller, target-pages
              * however the source ensures it always sends all the components
              * of a host page in order.
              */
             page_buffer = postcopy_host_page +
-                          ((uintptr_t)host & ~qemu_host_page_mask);
+                          ((uintptr_t)host & (block->page_size - 1));
             /* If all TP are zero then we can optimise the place */
-            if (!((uintptr_t)host & ~qemu_host_page_mask)) {
+            if (!((uintptr_t)host & (block->page_size - 1))) {
                 all_zero = true;
             } else {
                 /* not the 1st TP within the HP */
@@ -2449,7 +2452,7 @@ static int ram_load_postcopy(QEMUFile *f)
              * page
              */
             place_needed = (((uintptr_t)host + TARGET_PAGE_SIZE) &
-                                     ~qemu_host_page_mask) == 0;
+                                     (block->page_size - 1)) == 0;
             place_source = postcopy_host_page;
         }
         last_host = host;