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Message-ID: <e6139ffa-92e5-8247-ba0b-71def4795104@loongson.cn>
Date:   Tue, 1 Aug 2023 09:22:25 +0800
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Subject: Re: [PATCH 3/3] LoongArch: mm: Add unified function
 populate_kernel_pte
Content-Language: en-US
To:     Huacai Chen <chenhuacai@kernel.org>
Cc:     Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
        Christoph Lameter <cl@linux.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        loongarch@lists.linux.dev, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, WANG Xuerui <kernel@xen0n.name>
References: <20230712031622.1888321-1-maobibo@loongson.cn>
 <20230712031622.1888321-4-maobibo@loongson.cn>
 <CAAhV-H5pHoFo7i8EpacLU=AWKKPckssJN1aThi+Bb8PPHn0gkA@mail.gmail.com>
From:   bibo mao <maobibo@loongson.cn>
In-Reply-To: <CAAhV-H5pHoFo7i8EpacLU=AWKKPckssJN1aThi+Bb8PPHn0gkA@mail.gmail.com>
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在 2023/7/31 22:15, Huacai Chen 写道:
> On Wed, Jul 12, 2023 at 11:16 AM Bibo Mao <maobibo@loongson.cn> 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@loongson.cn>
>> ---
>>  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().
Can you share me the points that pte table must be allocated with memblock_alloc_low
in this place?

Regards
Bibo Mao
> 
> 
> 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
>>