Commit 6e799cb6 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

mm/highmem: Provide and use CONFIG_DEBUG_KMAP_LOCAL 



CONFIG_KMAP_LOCAL can be enabled by x86/32bit even if CONFIG_HIGHMEM is not
enabled for temporary MMIO space mappings.

Provide it as a seperate config option which depends on CONFIG_KMAP_LOCAL
and let CONFIG_DEBUG_HIGHMEM select it.

This won't increase the debug coverage of this significantly but it paves
the way to do so.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204006.869487226@linutronix.de
parent 13c8da5d

include/asm-generic/kmap_size.h

+1 −1
Original line number Diff line number Diff line
@@ -3,7 +3,7 @@ 
#define _ASM_GENERIC_KMAP_SIZE_H



/* For debug this provides guard pages between the maps */

#ifdef CONFIG_DEBUG_HIGHMEM

#ifdef CONFIG_DEBUG_KMAP_LOCAL

# define KM_MAX_IDX	33

#else

# define KM_MAX_IDX	16

lib/Kconfig.debug

+8 −0
Original line number Diff line number Diff line
@@ -849,9 +849,17 @@ config DEBUG_PER_CPU_MAPS 


	  Say N if unsure.



config DEBUG_KMAP_LOCAL

	bool "Debug kmap_local temporary mappings"

	depends on DEBUG_KERNEL && KMAP_LOCAL

	help

	  This option enables additional error checking for the kmap_local

	  infrastructure.  Disable for production use.



config DEBUG_HIGHMEM

	bool "Highmem debugging"

	depends on DEBUG_KERNEL && HIGHMEM

	select DEBUG_KMAP_LOCAL

	help

	  This option enables additional error checking for high memory

	  systems.  Disable for production systems.

mm/highmem.c

+2 −2
Original line number Diff line number Diff line
@@ -368,10 +368,10 @@ EXPORT_SYMBOL(kunmap_high); 
static DEFINE_PER_CPU(int, __kmap_local_idx);



/*

 * With DEBUG_HIGHMEM the stack depth is doubled and every second

 * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second

 * slot is unused which acts as a guard page

 */

#ifdef CONFIG_DEBUG_HIGHMEM

#ifdef CONFIG_DEBUG_KMAP_LOCAL

# define KM_INCR	2

#else

# define KM_INCR	1