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

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

[Chuanhua Han]

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: Chuanhua Han <hanchuanhua@fishsemi.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 be84e32adc4c..24f4ebfd2df8 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -208,9 +208,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 vmalloc_fault:
 	{
 		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;
 
@@ -234,12 +234,10 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 			goto no_context;
 		set_pgd(pgd, *pgd_k);
 
-		p4d = p4d_offset(pgd, addr);
 		p4d_k = p4d_offset(pgd_k, addr);
 		if (!p4d_present(*p4d_k))
 			goto no_context;
 
-		pud = pud_offset(p4d, addr);
 		pud_k = pud_offset(p4d_k, addr);
 		if (!pud_present(*pud_k))
 			goto no_context;
@@ -248,11 +246,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
 		 * 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))
 			goto no_context;
-		set_pmd(pmd, *pmd_k);
 
 		/*
 		 * Make sure the actual PTE exists as well to
-- 
2.17.1

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

[Alex Ghiti]

Le 3/30/20 à 7:53 AM, Chuanhua Han a écrit :
> 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: Chuanhua Han <hanchuanhua@fishsemi.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 be84e32adc4c..24f4ebfd2df8 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -208,9 +208,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>   vmalloc_fault:
>   	{
>   		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;
>   
> @@ -234,12 +234,10 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>   			goto no_context;
>   		set_pgd(pgd, *pgd_k);
>   
> -		p4d = p4d_offset(pgd, addr);
>   		p4d_k = p4d_offset(pgd_k, addr);
>   		if (!p4d_present(*p4d_k))
>   			goto no_context;
>   
> -		pud = pud_offset(p4d, addr);
>   		pud_k = pud_offset(p4d_k, addr);
>   		if (!pud_present(*pud_k))
>   			goto no_context;
> @@ -248,11 +246,9 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
>   		 * 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))
>   			goto no_context;
> -		set_pmd(pmd, *pmd_k);
>   
>   		/*
>   		 * Make sure the actual PTE exists as well to
> 

Better late than never: I do agree with this patch, once the PGD is 
copied into the user page table, it "comes with all its mappings" so 
there is no need to copy PMD, the only thing left to do is to make sure 
the mapping does exists in the kernel page table.

So feel free to add:

Reviewed-by: Alexandre Ghiti <alex@ghiti.fr>
Tested-by: Alexandre Ghiti <alex@ghiti.fr>

Thanks,

Alex

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

[hanchuanhua]

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!

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

[Palmer Dabbelt]

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!

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

[hanchuanhua]

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
--
2.7.4

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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!