Re: [PATCH -next] arm64: fix -Wundef warning for PUD_SHIFT

[zhangjianhua (E)]

在 2023/7/24 11:26, Anshuman Khandual 写道:
> On 7/24/23 16:00, 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 at this time PUD_SHIFT is equal to PGDIR_SHIFT, so define it.
> CONFIG_PGTABLE_LEVELS equals 3 only with CONFIG_VA_BITS = 39.
>
> > Fixes: 06e9bf2fd9b3 ("arm64: choose memstart_addr based on minimum sparsemem section alignment")
> This is not a fix, ARM64_MEMSTART_ALIGN would fallback being (1UL << SECTION_SIZE_BITS)
> when PUD_SHIFT is undefined (aka 0) but agreed that it's not clean.
Yes, it wouldn't be wrong in the end.
> > Signed-off-by: Zhang Jianhua <chris.zjh@xxxxxxxxxx>
> > ---
> > v2:
> > 	Define PUD_SHIFT before use it instead of judgement
> > ---
> > ---
> >   arch/arm64/include/asm/kernel-pgtable.h | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
> > index 577773870b66..996a144e2929 100644
> > --- a/arch/arm64/include/asm/kernel-pgtable.h
> > +++ b/arch/arm64/include/asm/kernel-pgtable.h
> > @@ -59,6 +59,10 @@
> >   #define EARLY_KASLR	(0)
> >   #endif
> >   
> > +#ifndef PUD_SHIFT
> > +#define PUD_SHIFT PGDIR_SHIFT
> > +#endif
> Rather ARM64_MEMSTART_SHIFT block needs to be re-written in a more pgtable levels agnostic
> manner ? OR maybe something like this.
>
> diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
> index 577773870b66..5a83b4b249e8 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
> -#elif defined(CONFIG_ARM64_16K_PAGES)
> +#elif defined(CONFIG_ARM64_16K_PAGES) && defined(CONT_PMD_SHIFT)
>   #define ARM64_MEMSTART_SHIFT           CONT_PMD_SHIFT
> -#else
> +#elif defined(CONFIG_AR64_64K_PAGES) && defined(PMD_SHIFT)
>   #define ARM64_MEMSTART_SHIFT           PMD_SHIFT
> +#else
> +#define ARM64_MEMSTART_SHIFT           PGDIR_SHIFT
>   #endif
>
> The only cases where PUD_SHIFT or PMD_SHIFT (along with CONT_PMD_SHIFT) would not be defined is
> when XXX_SHIFT level itself matches PGDIR_SHIFT.
Thanks for your reply, this modification seems more comprehensive and 
appropriate. I will send v2 patch soon.
> > +
> >   #define SPAN_NR_ENTRIES(vstart, vend, shift) \
> >   	((((vend) - 1) >> (shift)) - ((vstart) >> (shift)) + 1)