[PATCH v4 3/7] arm64: Introduce a kernel configuration option for VA_BITS

[PATCH v4 3/7] arm64: Introduce a kernel configuration option for VA_BITS

[Jungseok Lee]

This patch adds a kernel configuration for VA_BITS.

It helps to prevent unnecessary #ifdef statements insertions
for VA_BITS when implementing different page sizes and level of
translation tables.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Steve Capper <steve.capper@linaro.org>
Signed-off-by: Jungseok Lee <jays.lee@samsung.com>
Reviewed-by: Sungjinn Chung <sungjinn.chung@samsung.com>
---
 arch/arm64/Kconfig              |    8 ++++++++
 arch/arm64/include/asm/memory.h |    6 +-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c7f5d65..7b8d429 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -186,6 +186,14 @@ config ARM64_3_LEVELS
 
 endchoice
 
+config ARM64_VA_BITS
+	int "Virtual address space size"
+	range 39 39 if ARM64_4K_PAGES && ARM64_3_LEVELS
+	range 42 42 if ARM64_64K_PAGES && ARM64_2_LEVELS
+	help
+	  This feature is determined by a combination of page size and
+	  level of translation tables.
+
 config CPU_BIG_ENDIAN
        bool "Build big-endian kernel"
        help
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index e94f945..f6e7480 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -41,11 +41,7 @@
  * The module space lives between the addresses given by TASK_SIZE
  * and PAGE_OFFSET - it must be within 128MB of the kernel text.
  */
-#ifdef CONFIG_ARM64_64K_PAGES
-#define VA_BITS			(42)
-#else
-#define VA_BITS			(39)
-#endif
+#define VA_BITS			(CONFIG_ARM64_VA_BITS)
 #define PAGE_OFFSET		(UL(0xffffffffffffffff) << (VA_BITS - 1))
 #define MODULES_END		(PAGE_OFFSET)
 #define MODULES_VADDR		(MODULES_END - SZ_64M)
-- 
1.7.10.4

Re: [PATCH v4 3/7] arm64: Introduce a kernel configuration option for VA_BITS

[Catalin Marinas]

On Tue, Apr 29, 2014 at 05:59:23AM +0100, Jungseok Lee wrote:
> +config ARM64_VA_BITS
> +	int "Virtual address space size"
> +	range 39 39 if ARM64_4K_PAGES && ARM64_3_LEVELS
> +	range 42 42 if ARM64_64K_PAGES && ARM64_2_LEVELS
> +	help
> +	  This feature is determined by a combination of page size and
> +	  level of translation tables.

OK, so you are doing the VA bits selection already. But see my other
email about setting only exposing this and hiding the number of levels
(though number of levels can be mentioned in the help).

-- 
Catalin

Re: [PATCH v4 3/7] arm64: Introduce a kernel configuration option for VA_BITS

[Jungseok Lee]

On Tuesday, April 29, 2014 11:45 PM, Catalin Marinas wrote:
> On Tue, Apr 29, 2014 at 05:59:23AM +0100, Jungseok Lee wrote:
> > +config ARM64_VA_BITS
> > +	int "Virtual address space size"
> > +	range 39 39 if ARM64_4K_PAGES && ARM64_3_LEVELS
> > +	range 42 42 if ARM64_64K_PAGES && ARM64_2_LEVELS
> > +	help
> > +	  This feature is determined by a combination of page size and
> > +	  level of translation tables.
> 
> OK, so you are doing the VA bits selection already. But see my other
> email about setting only exposing this and hiding the number of levels
> (though number of levels can be mentioned in the help).

Okay. I will hide the number of levels.

Best Regards
Jungseok Lee