Re: [PATCH -next v2] arm64: fix build warning for ARM64_MEMSTART_SHIFT

["zhangjianhua (E)" <chris.zjh@huawei.com>]

在 2023/7/25 18:15, Catalin Marinas 写道:
> On Tue, Jul 25, 2023 at 04:47:46PM +0800, zhangjianhua (E) wrote:
>> 在 2023/7/25 12:22, Anshuman Khandual 写道:
>>> On 7/24/23 20:41, Catalin Marinas wrote:
>>>> On Mon, Jul 24, 2023 at 05:27:51PM +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
>>>>>         |     ^~~~~~~~~~~~~~~~~~~~
>>>> Another thing that's missing here is that the warning is probably when
>>>> this file is included from asm-offests.h or some .S file.
>>>>
>>>>> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
>>>>> index 577773870b66..51bdce66885d 100644
>>>>> --- a/arch/arm64/include/asm/kernel-pgtable.h
>>>>> +++ b/arch/arm64/include/asm/kernel-pgtable.h
>>>>> @@ -125,12 +125,14 @@
>>>>>     * (64k granule), or a multiple that can be mapped using contiguous bits
>>>>>     * in the page tables: 32 * PMD_SIZE (16k granule)
>>>>>     */
>>>>> -#if defined(CONFIG_ARM64_4K_PAGES)
>>>>> +#if defined(CONFIG_ARM64_4K_PAGES) && defined(PUD_SHIFT)
>>>>>    #define ARM64_MEMSTART_SHIFT		PUD_SHIFT
>>>> That's not the correct fix since PUD_SHIFT should always be defined.
>>>> When CONFIG_PGTABLE_LEVELS == 3, pgtable-types.h includes
>>>> asm-generic/pgtable-nopud.h and this defines PUD_SHIFT. We either got
>>> Right, PUD_SHIFT is always defined irrespective of page table levels.
>>>
>>>> ARM64_MEMSTART_SHIFT defined in the wrong file or kernel-pgtable.h does
>>>> not pull the relevant headers (either directly or via an included
>>>> header). Even if kernel-pgtable.h ends up including the nopud/nopmd
>>>> headers, P*D_SHIFT is guarded by an #indef __ASSEMBLY__ in those files.
>>>>
>>>> Something like below appears to fix this, though I'm not particularly
>>>> fond of guarding the ARM64_MEMSTART_* definitions by #ifndef
>>>> __ASSEMBLY__ for no apparent reason (could add a comment though):
>>>>
>>>> -----------------------8<---------------------------
>>>> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
>>>> index 577773870b66..fcea7e87a6ca 100644
>>>> --- a/arch/arm64/include/asm/kernel-pgtable.h
>>>> +++ b/arch/arm64/include/asm/kernel-pgtable.h
>>>> @@ -118,6 +118,8 @@
>>>>    #define SWAPPER_RX_MMUFLAGS	(SWAPPER_RW_MMUFLAGS | PTE_RDONLY)
>>>>    #endif
>>>> +#ifndef __ASSEMBLY__
>>>> +
>>>>    /*
>>>>     * To make optimal use of block mappings when laying out the linear
>>>>     * mapping, round down the base of physical memory to a size that can
>>>> @@ -145,4 +147,6 @@
>>>>    #define ARM64_MEMSTART_ALIGN	(1UL << ARM64_MEMSTART_SHIFT)
>>>>    #endif
>>>> +#endif /* __ASSEMBLY__ */
>>>> +
>>>>    #endif	/* __ASM_KERNEL_PGTABLE_H */
>>>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
>>>> index e4944d517c99..22b36f2d5d93 100644
>>>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>>>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>>>> @@ -6,6 +6,7 @@
>>>>    #define __ASM_PGTABLE_HWDEF_H
>>>>    #include <asm/memory.h>
>>>> +#include <asm/pgtable-types.h>
>>>>    /*
>>>>     * Number of page-table levels required to address 'va_bits' wide
>>>> diff --git a/arch/arm64/include/asm/pgtable-types.h b/arch/arm64/include/asm/pgtable-types.h
>>>> index b8f158ae2527..ae86e66fdb11 100644
>>>> --- a/arch/arm64/include/asm/pgtable-types.h
>>>> +++ b/arch/arm64/include/asm/pgtable-types.h
>>>> @@ -11,6 +11,8 @@
>>>>    #include <asm/types.h>
>>>> +#ifndef __ASSEMBLY__
>>>> +
>>>>    typedef u64 pteval_t;
>>>>    typedef u64 pmdval_t;
>>>>    typedef u64 pudval_t;
>>>> @@ -44,6 +46,8 @@ typedef struct { pteval_t pgprot; } pgprot_t;
>>>>    #define pgprot_val(x)	((x).pgprot)
>>>>    #define __pgprot(x)	((pgprot_t) { (x) } )
>>>> +#endif /* __ASSEMBLY__ */
>>>> +
>>>>    #if CONFIG_PGTABLE_LEVELS == 2
>>>>    #include <asm-generic/pgtable-nopmd.h>
>>>>    #elif CONFIG_PGTABLE_LEVELS == 3
>>>> -----------------------8<---------------------------
>>>>
>>>> To avoid guarding the ARM64_MEMSTART_* definitions, we could instead
>>>> move the P*D_SHIFT definitions in asm-generic/pgtable-nop*d.h outside
>>>> the #ifndef __ASSEMBLY__ block.
>>> OR could ARM64_MEMSTART_SHIFT and ARM64_MEMSTART_ALIGN computation blocks
>>> be moved inside arch/arm64/mm/init.c, where it is used exclusively. Seems
>>> to be solving the problem as well.
> That's fine by me, better than adding the #ifndef __ASSEMBLY__ around
> them.
>
>> This method can avoid the current compilation warning, but does not
>> solve the problem that PUD_SHIFT and PMD_SHIFT undefined in fact, and
>> it is contrary to XXX_SHIFT should always be defined. Maybe it would
>> be more appropriate to solve this issue directly.
> For .c files, we can solve this by including asm/pgtable-types.h in
> asm/pgtable-hwdef.h. This still leaves P*D_SHIFT undefined for .S files
> since the generic nop*d.h headers guard the shifts with !__ASSEMBLY__
> but do we really care about this? I haven't seen any other warning of
> P*D_SHIFT not being defined. If you do want to solve these, just go and
> change the generic headers to take the shift out of the asm guard. I
> don't think it's worth it.
OK, agree, I will send a new patch for Anshuman's method.