Re: [PATCH 2/3] LoongArch: Code cleanup in function pcpu_populate_pte

bibo mao
2023-08-01T01:18:34Z

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:
>>
>> There are some code cleanups in function pcpu_populate_pte:
>> 1. Replace memblock_alloc with memblock_alloc_raw for pud and pmd since
>> they will be reinitialized with pud_init and pmd_init.
>>
>> 2. Add memory allocation failure handling
>>
>> 3. Replace pgd_populate with p4d_populate, it will be useful if there
>> four-level page tables.
>>
>> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
>> ---
>> arch/loongarch/kernel/numa.c | 33 ++++++++++++++++++++-------------
>> 1 file changed, 20 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/loongarch/kernel/numa.c b/arch/loongarch/kernel/numa.c
>> index 708665895b47..778e1c20bfb0 100644
>> --- a/arch/loongarch/kernel/numa.c
>> +++ b/arch/loongarch/kernel/numa.c
>> @@ -73,33 +73,40 @@ void __init pcpu_populate_pte(unsigned long addr)
>> pmd_t *pmd;
>>
>> if (p4d_none(*p4d)) {
>> - pud_t *new;
>> -
>> - new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>> - pgd_populate(&init_mm, pgd, new);
>> + pud = memblock_alloc_raw(PAGE_SIZE, PAGE_SIZE);
> Don't use memblock_alloc_raw() here, it is better to keep consistency
> with mm/percpu.c.
memblock_alloc will clear the page, and there will be page table initialization
with the following pud_init(pud). memblock_alloc_raw will not clear the page.

I prefer memblock_alloc_raw for better performance however ok with both, it is
up to you to decide.

Regards
Bibo Mao

>
>
> Huacai
>> + 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;
>> -
>> - new = memblock_alloc(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_present(*pmd)) {
>> - pte_t *new;
>> + pte_t *pte;
>>
>> - new = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>> - pmd_populate_kernel(&init_mm, pmd, new);
>> + pte = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>> + if (!pte)
>> + goto err_alloc;
>> + pmd_populate_kernel(&init_mm, pmd, pte);
>> }
>> +
>> + return;
>> +
>> +err_alloc:
>> + panic("%s: Failed to allocate memory\n", __func__);
>> }
>>
>> void __init setup_per_cpu_areas(void)
>> --
>> 2.27.0
>>