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/20260429102704.680174-4-dev.jain@arm.com
Signed-off-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ben Segall <bsegall@google.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Kees Cook <kees@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
index 57137d3ac159259e8c5d8f94b8c6c46144d08d9e..051aa1331051c6527e49c44b1954f82579e23aee 100644 (file)
--- a/include/asm-generic/pgalloc.h
+++ b/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)
 
 /**