Re: [PATCH 3/3] LoongArch: mm: Add unified function populate_kernel_pte

[Huacai Chen]

On Wed, Jul 12, 2023 at 11:16 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
>
> Function pcpu_populate_pte and fixmap_pte are similar, they populate
> one page from kernel address space. And there is confusion between
> pgd and p4d in function fixmap_pte, such as pgd_none always returns
> zero. This patch adds unified function populate_kernel_pte and replaces
> pcpu_populate_pte and fixmap_pte.
>
> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> ---
>  arch/loongarch/include/asm/pgalloc.h |  1 +
>  arch/loongarch/kernel/numa.c         | 40 +--------------------
>  arch/loongarch/mm/init.c             | 52 ++++++++++++++++------------
>  3 files changed, 32 insertions(+), 61 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/pgalloc.h b/arch/loongarch/include/asm/pgalloc.h
> index af1d1e4a6965..ca17b573dba6 100644
> --- a/arch/loongarch/include/asm/pgalloc.h
> +++ b/arch/loongarch/include/asm/pgalloc.h
> @@ -91,4 +91,5 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long address)
>
>  #endif /* __PAGETABLE_PUD_FOLDED */
>
> +extern pte_t * __init populate_kernel_pte(unsigned long addr);
>  #endif /* _ASM_PGALLOC_H */
> diff --git a/arch/loongarch/kernel/numa.c b/arch/loongarch/kernel/numa.c
> index 778e1c20bfb0..24a693b76873 100644
> --- a/arch/loongarch/kernel/numa.c
> +++ b/arch/loongarch/kernel/numa.c
> @@ -67,46 +67,8 @@ static int __init pcpu_cpu_distance(unsigned int from, unsigned int to)
>
>  void __init pcpu_populate_pte(unsigned long addr)
>  {
> -       pgd_t *pgd = pgd_offset_k(addr);
> -       p4d_t *p4d = p4d_offset(pgd, addr);
> -       pud_t *pud;
> -       pmd_t *pmd;
> -
> -       if (p4d_none(*p4d)) {
> -               pud = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
> -               if (!pud)
> -                       goto err_alloc;
> -               p4d_populate(&init_mm, p4d, pud);
> -#ifndef __PAGETABLE_PUD_FOLDED
> -               pud_init(pud);
> -#endif
> -       }
> -
> -       pud = pud_offset(p4d, addr);
> -       if (pud_none(*pud)) {
> -               pmd = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
> -               if (!pmd)
> -                       goto err_alloc;
> -               pud_populate(&init_mm, pud, pmd);
> -#ifndef __PAGETABLE_PMD_FOLDED
> -               pmd_init(pmd);
> -#endif
> -       }
> -
> -       pmd = pmd_offset(pud, addr);
> -       if (!pmd_present(*pmd)) {
> -               pte_t *pte;
> -
> -               pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
> -               if (!pte)
> -                       goto err_alloc;
> -               pmd_populate_kernel(&init_mm, pmd, pte);
> -       }
> -
> +       populate_kernel_pte(addr);
>         return;
> -
> -err_alloc:
> -       panic("%s: Failed to allocate memory\n", __func__);
>  }
>
>  void __init setup_per_cpu_areas(void)
> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
> index 3b7d8129570b..6cd2948373ae 100644
> --- a/arch/loongarch/mm/init.c
> +++ b/arch/loongarch/mm/init.c
> @@ -191,46 +191,49 @@ void vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *al
>  #endif
>  #endif
>
> -static pte_t *fixmap_pte(unsigned long addr)
> +pte_t * __init populate_kernel_pte(unsigned long addr)
>  {
> -       pgd_t *pgd;
> -       p4d_t *p4d;
> +       pgd_t *pgd = pgd_offset_k(addr);
> +       p4d_t *p4d = p4d_offset(pgd, addr);
>         pud_t *pud;
>         pmd_t *pmd;
>
> -       pgd = pgd_offset_k(addr);
> -       p4d = p4d_offset(pgd, addr);
> -
> -       if (pgd_none(*pgd)) {
> -               pud_t *new __maybe_unused;
> -
> -               new = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
> -               pgd_populate(&init_mm, pgd, new);
> +       if (p4d_none(*p4d)) {
> +               pud = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
> +               if (!pud)
> +                       goto err_alloc;
> +               p4d_populate(&init_mm, p4d, pud);
>  #ifndef __PAGETABLE_PUD_FOLDED
> -               pud_init(new);
> +               pud_init(pud);
>  #endif
>         }
>
>         pud = pud_offset(p4d, addr);
>         if (pud_none(*pud)) {
> -               pmd_t *new __maybe_unused;
> -
> -               new = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
> -               pud_populate(&init_mm, pud, new);
> +               pmd = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
> +               if (!pmd)
> +                       goto err_alloc;
> +               pud_populate(&init_mm, pud, pmd);
>  #ifndef __PAGETABLE_PMD_FOLDED
> -               pmd_init(new);
> +               pmd_init(pmd);
>  #endif
>         }
>
>         pmd = pmd_offset(pud, addr);
> -       if (pmd_none(*pmd)) {
> -               pte_t *new __maybe_unused;
> +       if (!pmd_present(*pmd)) {
> +               pte_t *pte;
>
> -               new = memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
> -               pmd_populate_kernel(&init_mm, pmd, new);
> +               pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
I don't think memblock_alloc_low() here can be replaced by memblock_alloc().


Huacai
> +               if (!pte)
> +                       goto err_alloc;
> +               pmd_populate_kernel(&init_mm, pmd, pte);
>         }
>
>         return pte_offset_kernel(pmd, addr);
> +
> +err_alloc:
> +       panic("%s: Failed to allocate memory\n", __func__);
> +       return NULL;
>  }
>
>  void __init __set_fixmap(enum fixed_addresses idx,
> @@ -241,7 +244,12 @@ void __init __set_fixmap(enum fixed_addresses idx,
>
>         BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
>
> -       ptep = fixmap_pte(addr);
> +       /*
> +        * Now only FIX_EARLYCON_MEM_BASE fixed map is used
> +        * __set_fixmap must be called before mem_init since function
> +        * populate_kernel_pte allocates memory with memblock_alloc method.
> +        */
> +       ptep = populate_kernel_pte(addr);
>         if (!pte_none(*ptep)) {
>                 pte_ERROR(*ptep);
>                 return;
> --
> 2.27.0
>