[PATCH] gnttab: don't allocate status frame tracking array when "gnttab=max_ver:1"

[Jan Beulich <jbeulich@xxxxxxxx>]

This array can be large when many grant frames are permitted; avoid
allocating it when it's not going to be used anyway. Do so indirectly
though, by making grant_to_status_frames() return zero in this case.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -446,11 +446,14 @@ static inline void active_entry_release(
 
 static inline unsigned int grant_to_status_frames(unsigned int grant_frames)
 {
+    if ( opt_gnttab_max_version < 2 )
+        return 0;
     return DIV_ROUND_UP(grant_frames * GRANT_PER_PAGE, GRANT_STATUS_PER_PAGE);
 }
 
 static inline unsigned int status_to_grant_frames(unsigned int status_frames)
 {
+    ASSERT(opt_gnttab_max_version >= 2);
     return DIV_ROUND_UP(status_frames * GRANT_STATUS_PER_PAGE, GRANT_PER_PAGE);
 }