Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <b4b21efb-a0c7-4625-91e7-4d0c5b80a249@loongson.cn>
Date:   Thu, 10 Aug 2023 12:08:54 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.13.0
Subject: Re: [PATCH 3/3] LoongArch: mm: Add unified function
 populate_kernel_pte
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>
 <e6139ffa-92e5-8247-ba0b-71def4795104@loongson.cn>
 <CAAhV-H7Y9SGaLA3+x8-kMg0eWW3UeGLTGMnmcTp7xftJPiJSoA@mail.gmail.com>
Content-Language: en-US
From:   bibo mao <maobibo@loongson.cn>
In-Reply-To: <CAAhV-H7Y9SGaLA3+x8-kMg0eWW3UeGLTGMnmcTp7xftJPiJSoA@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk


在 2023/8/2 15:25, Huacai Chen 写道:
> On Tue, Aug 1, 2023 at 9:22 AM bibo mao <maobibo@loongson.cn> wrote:
>>
>>
>>
>> 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?
> I forget the reason now, so if you confirm memblock_alloc() works well
> here, you can use it. But please don't use memblock_alloc_raw().
what a mess, there is more comments if there is special reason, else everyone can
forgot by elapsed time.

why the function memblock_alloc_raw can not be use? there is one useless page copy.

Regards
Bibo Mao


> 
> Huacai
>>
>> 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
>>>>
>>
>>