LoongArch: use 40 bits address space for user

LoongArch inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6BWFP

--------------------------------

default to use 40 bits address space for user.
Signed-off-by: NHongchen Zhang <zhanghongchen@loongson.cn>
Change-Id: I23088f43e700ed9b4eb15df2cc9c58299a0582ff
(cherry picked from commit 0dde507c)

arch/loongarch/Kconfig

@@ -426,6 +426,13 @@ config NODES_SHIFT
 	default "6"
 	depends on NUMA
 
+config VA_BITS_40
+	bool "40-bits"
+	default y
+	depends on 64BIT
+	help
+	  Support a maximum at least 40 bits of application virtual memory.
+
 config FORCE_MAX_ZONEORDER
 	int "Maximum zone order"
 	range 14 64 if PAGE_SIZE_64KB

arch/loongarch/include/asm/pgtable.h

@@ -42,7 +42,11 @@
 #define PGDIR_SIZE	(1UL << PGDIR_SHIFT)
 #define PGDIR_MASK	(~(PGDIR_SIZE-1))
 
+#ifdef CONFIG_VA_BITS_40
+#define VA_BITS		40
+#else
 #define VA_BITS		(PGDIR_SHIFT + (PAGE_SHIFT - 3))
+#endif
 
 #define PTRS_PER_PGD	(PAGE_SIZE >> 3)
 #if CONFIG_PGTABLE_LEVELS > 3