Re: [PATCH -next v3] arm64: fix build warning for ARM64_MEMSTART_SHIFT

From: Catalin Marinas
Date: Thu Aug 03 2023 - 13:06:17 EST


On Tue, Jul 25, 2023 at 08:24:04PM +0000, Zhang Jianhua wrote:
> When building with W=1, the following warning occurs.
>
> arch/arm64/include/asm/kernel-pgtable.h:129:41: error: "PUD_SHIFT" is not defined, evaluates to 0 [-Werror=undef]
> 129 | #define ARM64_MEMSTART_SHIFT PUD_SHIFT
> | ^~~~~~~~~
> arch/arm64/include/asm/kernel-pgtable.h:142:5: note: in expansion of macro ‘ARM64_MEMSTART_SHIFT’
> 142 | #if ARM64_MEMSTART_SHIFT < SECTION_SIZE_BITS
> | ^~~~~~~~~~~~~~~~~~~~
>
> The reason is that PUD_SHIFT isn't defined if CONFIG_PGTABLE_LEVELS == 3
> and CONFIG_VA_BITS == 39.

The correct description is that the generic PUD_SHIFT isn't defined for
asm files, we still have it defined for C files (there's an #ifndef
__ASSEMBLY__ guard).

> Now move the macro ARM64_MEMSTART_SHIFT and
> ARM64_MEMSTART_ALIGN to arch/arm64/mm/init.c where it is used to avoid
> this issue, and also there is no other place to call these two macro.
>
> Signed-off-by: Zhang Jianhua <chris.zjh@xxxxxxxxxx>

This fix works for me. I'll leave it to Will for 6.6 as apart from the
warning with W=1, there's no other issue (ARM64_MEMSTART_* are not used
in any asm files).

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>