Re: [PATCH v2 04/13] arm64: decouple early fixmap init from linear mapping

Catalin Marinas
2016-01-08T12:00:17Z

On Wed, Dec 30, 2015 at 04:26:03PM +0100, Ard Biesheuvel wrote:
> @@ -583,33 +555,42 @@ void __init early_fixmap_init(void)
> unsigned long addr = FIXADDR_START;
>
> pgd = pgd_offset_k(addr);
> - pgd_populate(&init_mm, pgd, bm_pud);
> - pud = pud_offset(pgd, addr);
> - pud_populate(&init_mm, pud, bm_pmd);
> - pmd = pmd_offset(pud, addr);
> - pmd_populate_kernel(&init_mm, pmd, bm_pte);
> +#if CONFIG_PGTABLE_LEVELS > 3
> + if (pgd_none(*pgd)) {
> + static pud_t bm_pud[PTRS_PER_PUD] __pgdir;
> +
> + pgd_populate(&init_mm, pgd, bm_pud);
> + memblock_reserve(__pa(bm_pud), sizeof(bm_pud));
> + }
> + pud = (pud_t *)__phys_to_kimg(pud_offset_phys(pgd, addr));
> +#else
> + pud = (pud_t *)pgd;
> +#endif
> +#if CONFIG_PGTABLE_LEVELS > 2
> + if (pud_none(*pud)) {
> + static pmd_t bm_pmd[PTRS_PER_PMD] __pgdir;
> +
> + pud_populate(&init_mm, pud, bm_pmd);
> + memblock_reserve(__pa(bm_pmd), sizeof(bm_pmd));
> + }
> + pmd = (pmd_t *)__phys_to_kimg(pmd_offset_phys(pud, addr));
> +#else
> + pmd = (pmd_t *)pud;
> +#endif
> + if (pmd_none(*pmd)) {
> + static pte_t bm_pte[PTRS_PER_PTE] __pgdir;
> +
> + pmd_populate_kernel(&init_mm, pmd, bm_pte);
> + memblock_reserve(__pa(bm_pte), sizeof(bm_pte));
> + }
> + __fixmap_pte = (pte_t *)__phys_to_kimg(pmd_page_paddr(*pmd));

I haven't tried but could you not avoid the #if and just rely on the
pud_none() etc. definitions to be 0 and the compiler+linker optimising
the irrelevant code out?

--
Catalin