Re: [PATCH] riscv: mm: Remove the copy operation of pmd

[hanchuanhua <hanchuanhua@oppo.com>]

On 2022/2/23 5:25, Palmer Dabbelt wrote:
> On Thu, 27 Jan 2022 02:06:22 PST (-0800), hanchuanhua@oppo.com wrote:
>> Since all processes share the kernel address space,
>> we only need to copy pgd in case of a vmalloc page
>> fault exception, the other levels of page tables are
>> shared, so the operation of copying pmd is unnecessary.
>>
>> Signed-off-by: hanchuanhua <hanchuanhua@oppo.com>
>> ---
>>   arch/riscv/mm/fault.c | 10 +++-------
>>   1 file changed, 3 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
>> index 4e9efbe..40694f0 100644
>> --- a/arch/riscv/mm/fault.c
>> +++ b/arch/riscv/mm/fault.c
>> @@ -102,9 +102,9 @@ static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code
>>   static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
>>   {
>>          pgd_t *pgd, *pgd_k;
>> -       pud_t *pud, *pud_k;
>> -       p4d_t *p4d, *p4d_k;
>> -       pmd_t *pmd, *pmd_k;
>> +       pud_t *pud_k;
>> +       p4d_t *p4d_k;
>> +       pmd_t *pmd_k;
>>          pte_t *pte_k;
>>          int index;
>>          unsigned long pfn;
>> @@ -132,14 +132,12 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
>>          }
>>          set_pgd(pgd, *pgd_k);
>>
>> -       p4d = p4d_offset(pgd, addr);
>>          p4d_k = p4d_offset(pgd_k, addr);
>>          if (!p4d_present(*p4d_k)) {
>>                  no_context(regs, addr);
>>                  return;
>>          }
>>
>> -       pud = pud_offset(p4d, addr);
>>          pud_k = pud_offset(p4d_k, addr);
>>          if (!pud_present(*pud_k)) {
>>                  no_context(regs, addr);
>> @@ -150,13 +148,11 @@ static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long a
>>           * Since the vmalloc area is global, it is unnecessary
>>           * to copy individual PTEs
>>           */
>> -       pmd = pmd_offset(pud, addr);
>>          pmd_k = pmd_offset(pud_k, addr);
>>          if (!pmd_present(*pmd_k)) {
>>                  no_context(regs, addr);
>>                  return;
>>          }
>> -       set_pmd(pmd, *pmd_k);
>>
>>          /*
>>           * Make sure the actual PTE exists as well to
> This looks good, but "Signed off by" lines are supposed to have real
> names associated with them and this looks like a handle to me.  There
> also seems to be something broken with the email, as this is causing git
> to blow up, but for a small patch like this that's OK as I can resurrect
> it by hand.
>
> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com> # aside from the name
>
> Please send a v2 with the proper Signed off by line, as that's not
> something I'm supposed to just fix up myself.
>
> Thanks!

First of all, thank you for your review and reply. I don't quite
understand what's wrong with the line "Signed off by"?

Thanks!

________________________________
OPPO

本电子邮件及其附件含有OPPO公司的保密信息，仅限于邮件指明的收件人使用（包含个人及群组）。禁止任何人在未经授权的情况下以任何形式使用。如果您错收了本邮件，请立即以电子邮件通知发件人并删除本邮件及其附件。

This e-mail and its attachments contain confidential information from OPPO, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it!