mm: skip KASAN tagging for page-allocated page tables

Page tables are always accessed via the linear mapping with a match-all
tag, so HW-tag KASAN never checks them.  For page-allocated tables (PTEs
and PGDs etc), avoid the tag setup and poisoning overhead by using
__GFP_SKIP_KASAN.  SLUB-backed page tables are unchanged for now.  (They
aren't widely used and require more SLUB related skip logic.  Leave it
later.)

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Muhammad Usama Anjum <[email protected]>
Signed-off-by: Dev Jain <[email protected]>
Reviewed-by: Ryan Roberts <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Acked-by: David Hildenbrand (Arm) <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Ben Segall <[email protected]>
Cc: Dietmar Eggemann <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: K Prateek Nayak <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: "Uladzislau Rezki (Sony)" <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Vincent Guittot <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/asm-generic/pgalloc.h

@@ -4,7 +4,7 @@
 
 #ifdef CONFIG_MMU
 
-#define GFP_PGTABLE_KERNEL	(GFP_KERNEL | __GFP_ZERO)
+#define GFP_PGTABLE_KERNEL	(GFP_KERNEL | __GFP_ZERO | __GFP_SKIP_KASAN)
 #define GFP_PGTABLE_USER	(GFP_PGTABLE_KERNEL | __GFP_ACCOUNT)
 
 /**