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

From: bibo mao
Date: Thu Aug 10 2023 - 00:09:00 EST



在 2023/8/2 15:25, Huacai Chen 写道:
> On Tue, Aug 1, 2023 at 9:22 AM bibo mao <maobibo@xxxxxxxxxxx> wrote:
>>
>>
>>
>> 在 2023/7/31 22:15, Huacai Chen 写道:
>>> 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().
>> 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
>>>>
>>
>>