On Wed, 20 May 2020 16:20:05 +0300 Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
> The kbuild test robot reported the following warning:
>
> arch/sparc/mm/srmmu.c: In function 'srmmu_nocache_init':
> >> arch/sparc/mm/srmmu.c:300:9: error: variable 'pud' set but not used
> >> [-Werror=unused-but-set-variable]
> 300 | pud_t *pud;
>
> This warning is caused by misprint in the page table traversal in
> srmmu_nocache_init() function which accessed a PMD entry using PGD rather
> than PUD.
> Since sparc32 has only 3 page table levels, the PGD and PUD are essentially
> the same and usage of __nocache_fix() removed the type checking.
>
> Use PUD for the consistency and to silence the compiler warning.
>
> ...
>
> --- a/arch/sparc/mm/srmmu.c
> +++ b/arch/sparc/mm/srmmu.c
> @@ -304,7 +304,7 @@ static void __init srmmu_nocache_init(void)
> pgd = pgd_offset_k(vaddr);
> p4d = p4d_offset(__nocache_fix(pgd), vaddr);
> pud = pud_offset(__nocache_fix(p4d), vaddr);
> - pmd = pmd_offset(__nocache_fix(pgd), vaddr);
> + pmd = pmd_offset(__nocache_fix(pud), vaddr);
> pte = pte_offset_kernel(__nocache_fix(pmd), vaddr);
>
> pteval = ((paddr >> 4) | SRMMU_ET_PTE | SRMMU_PRIV);
I added
Fixes: 7235db268a2777bc38 ("sparc32: use pgtable-nopud instead of 4level-fixup")
and, after a bit of thought,
Cc: <stable@xxxxxxxxxxxxxxx>
Because that's a fairly scary-looking warning.
