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[PATCH 05/10] riscv: mm: Skip pgtable level check in {pud,p4d}_alloc_one

Kevin Brodsky posted 10 patches 12 months ago
There is a newer version of this series
[PATCH 05/10] riscv: mm: Skip pgtable level check in {pud,p4d}_alloc_one
Posted by Kevin Brodsky 12 months ago 
{pmd,pud,p4d}_alloc_one() is never called if the corresponding page
table level is folded, as {pmd,pud,p4d}_alloc() already does the
required check. We can therefore remove the runtime page table level
checks in {pud,p4d}_alloc_one. The PUD helper becomes equivalent to
the generic version, so we remove it altogether.

This is consistent with the way arm64 and x86 handle this situation
(runtime check in p4d_free() only).

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
 arch/riscv/include/asm/pgalloc.h | 22 ++++------------------
 1 file changed, 4 insertions(+), 18 deletions(-)

diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index f52264304f77..8ad0bbe838a2 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h
@@ -12,7 +12,6 @@
 #include <asm/tlb.h>
 
 #ifdef CONFIG_MMU
-#define __HAVE_ARCH_PUD_ALLOC_ONE
 #define __HAVE_ARCH_PUD_FREE
 #include <asm-generic/pgalloc.h>
 
@@ -88,15 +87,6 @@ static inline void pgd_populate_safe(struct mm_struct *mm, pgd_t *pgd,
 	}
 }
 
-#define pud_alloc_one pud_alloc_one
-static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
-{
-	if (pgtable_l4_enabled)
-		return __pud_alloc_one(mm, addr);
-
-	return NULL;
-}
-
 #define pud_free pud_free
 static inline void pud_free(struct mm_struct *mm, pud_t *pud)
 {
@@ -118,15 +108,11 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
 #define p4d_alloc_one p4d_alloc_one
 static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
 {
-	if (pgtable_l5_enabled) {
-		gfp_t gfp = GFP_PGTABLE_USER;
-
-		if (mm == &init_mm)
-			gfp = GFP_PGTABLE_KERNEL;
-		return (p4d_t *)get_zeroed_page(gfp);
-	}
+	gfp_t gfp = GFP_PGTABLE_USER;
 
-	return NULL;
+	if (mm == &init_mm)
+		gfp = GFP_PGTABLE_KERNEL;
+	return (p4d_t *)get_zeroed_page(gfp);
 }
 
 static inline void __p4d_free(struct mm_struct *mm, p4d_t *p4d)
-- 
2.47.0
Re: [PATCH 05/10] riscv: mm: Skip pgtable level check in {pud,p4d}_alloc_one
Posted by Alexandre Ghiti 11 months, 2 weeks ago 
Hi Kevin,

On 19/12/2024 17:44, Kevin Brodsky wrote:
> {pmd,pud,p4d}_alloc_one() is never called if the corresponding page
> table level is folded, as {pmd,pud,p4d}_alloc() already does the
> required check. We can therefore remove the runtime page table level
> checks in {pud,p4d}_alloc_one. The PUD helper becomes equivalent to
> the generic version, so we remove it altogether.
>
> This is consistent with the way arm64 and x86 handle this situation
> (runtime check in p4d_free() only).
>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
> ---
>   arch/riscv/include/asm/pgalloc.h | 22 ++++------------------
>   1 file changed, 4 insertions(+), 18 deletions(-)
>
> diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
> index f52264304f77..8ad0bbe838a2 100644
> --- a/arch/riscv/include/asm/pgalloc.h
> +++ b/arch/riscv/include/asm/pgalloc.h
> @@ -12,7 +12,6 @@
>   #include <asm/tlb.h>
>   
>   #ifdef CONFIG_MMU
> -#define __HAVE_ARCH_PUD_ALLOC_ONE
>   #define __HAVE_ARCH_PUD_FREE
>   #include <asm-generic/pgalloc.h>
>   
> @@ -88,15 +87,6 @@ static inline void pgd_populate_safe(struct mm_struct *mm, pgd_t *pgd,
>   	}
>   }
>   
> -#define pud_alloc_one pud_alloc_one
> -static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
> -{
> -	if (pgtable_l4_enabled)
> -		return __pud_alloc_one(mm, addr);
> -
> -	return NULL;
> -}
> -
>   #define pud_free pud_free
>   static inline void pud_free(struct mm_struct *mm, pud_t *pud)
>   {
> @@ -118,15 +108,11 @@ static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
>   #define p4d_alloc_one p4d_alloc_one
>   static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
>   {
> -	if (pgtable_l5_enabled) {
> -		gfp_t gfp = GFP_PGTABLE_USER;
> -
> -		if (mm == &init_mm)
> -			gfp = GFP_PGTABLE_KERNEL;
> -		return (p4d_t *)get_zeroed_page(gfp);
> -	}
> +	gfp_t gfp = GFP_PGTABLE_USER;
>   
> -	return NULL;
> +	if (mm == &init_mm)
> +		gfp = GFP_PGTABLE_KERNEL;
> +	return (p4d_t *)get_zeroed_page(gfp);
>   }
>   
>   static inline void __p4d_free(struct mm_struct *mm, p4d_t *p4d)


Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks,

Alex
Re: [PATCH 05/10] riscv: mm: Skip pgtable level check in {pud,p4d}_alloc_one
Posted by Kevin Brodsky 11 months, 2 weeks ago 
+Qi

On 03/01/2025 11:31, Alexandre Ghiti wrote:
> Hi Kevin,
>
> On 19/12/2024 17:44, Kevin Brodsky wrote:
>> {pmd,pud,p4d}_alloc_one() is never called if the corresponding page
>> table level is folded, as {pmd,pud,p4d}_alloc() already does the
>> required check. We can therefore remove the runtime page table level
>> checks in {pud,p4d}_alloc_one. The PUD helper becomes equivalent to
>> the generic version, so we remove it altogether.
>>
>> This is consistent with the way arm64 and x86 handle this situation
>> (runtime check in p4d_free() only).
>>
>> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
>> ---
>>   arch/riscv/include/asm/pgalloc.h | 22 ++++------------------
>>   1 file changed, 4 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/riscv/include/asm/pgalloc.h
>> b/arch/riscv/include/asm/pgalloc.h
>> index f52264304f77..8ad0bbe838a2 100644
>> --- a/arch/riscv/include/asm/pgalloc.h
>> +++ b/arch/riscv/include/asm/pgalloc.h
>> @@ -12,7 +12,6 @@
>>   #include <asm/tlb.h>
>>     #ifdef CONFIG_MMU
>> -#define __HAVE_ARCH_PUD_ALLOC_ONE
>>   #define __HAVE_ARCH_PUD_FREE
>>   #include <asm-generic/pgalloc.h>
>>   @@ -88,15 +87,6 @@ static inline void pgd_populate_safe(struct
>> mm_struct *mm, pgd_t *pgd,
>>       }
>>   }
>>   -#define pud_alloc_one pud_alloc_one
>> -static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned
>> long addr)
>> -{
>> -    if (pgtable_l4_enabled)
>> -        return __pud_alloc_one(mm, addr);
>> -
>> -    return NULL;
>> -}
>> -
>>   #define pud_free pud_free
>>   static inline void pud_free(struct mm_struct *mm, pud_t *pud)
>>   {
>> @@ -118,15 +108,11 @@ static inline void __pud_free_tlb(struct
>> mmu_gather *tlb, pud_t *pud,
>>   #define p4d_alloc_one p4d_alloc_one
>>   static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned
>> long addr)
>>   {
>> -    if (pgtable_l5_enabled) {
>> -        gfp_t gfp = GFP_PGTABLE_USER;
>> -
>> -        if (mm == &init_mm)
>> -            gfp = GFP_PGTABLE_KERNEL;
>> -        return (p4d_t *)get_zeroed_page(gfp);
>> -    }
>> +    gfp_t gfp = GFP_PGTABLE_USER;
>>   -    return NULL;
>> +    if (mm == &init_mm)
>> +        gfp = GFP_PGTABLE_KERNEL;
>> +    return (p4d_t *)get_zeroed_page(gfp);
>>   }
>>     static inline void __p4d_free(struct mm_struct *mm, p4d_t *p4d)
>
>
> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks for the review! Just FYI this patch is now part of Qi's series
[1], I will drop it when posting the next version of this series.

- Kevin

[1]
https://lore.kernel.org/linux-mm/84ddf857508b98a195a790bc6ff6ab8849b44633.1735549103.git.zhengqi.arch@bytedance.com/

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