xenpaging: start paging in the middle of gfn range

Set the starting gfn to somewhere in the middle of the gfn range to
avoid paging during BIOS startup. This can speedup booting of a guest.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

tools/xenpaging/policy_default.c

@@ -69,6 +69,10 @@ int policy_init(xenpaging_t *paging)
     /* Don't page out page 0 */
     set_bit(0, bitmap);
 
+    /* Start in the middle to avoid paging during BIOS startup */
+    current_gfn = max_pages / 2;
+    current_gfn -= paging->num_pages / 2;
+
     rc = 0;
  out:
     return rc;