arm64/mm: Drop PXD_TABLE_BIT

[PATCH 1/5] arm64/mm: Drop pte_mkhuge()

Posted by Anshuman Khandual 1 month, 3 weeks ago

Core HugeTLB defines arch_make_huge_pte() fallback definition, which calls
platform provided pte_mkhuge(). But if any platform already provides custom
arch_make_huge_pte(), then it does not need to provide pte_mkhuge(). arm64
defines arch_make_huge_pte(), but then also calls pte_mkhuge() internally.
This creates confusion as if both of these callbacks are being used in core
HugeTLB and required to be defined in the platform.

This changes arch_make_huge_pte() to create block mapping directly and also
drops off now redundant helper pte_mkhuge(), making things clear. Also this
changes HugeTLB page creation from just clearing the PTE_TABLE_BIT (bit[1])
to actually setting bits[1:0] via PTE_TYPE_[MASK|SECT] instead.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 arch/arm64/include/asm/pgtable-hwdef.h | 1 +
 arch/arm64/include/asm/pgtable.h       | 5 -----
 arch/arm64/mm/hugetlbpage.c            | 2 +-
 3 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index fd330c1db289..956a702cb532 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -158,6 +158,7 @@
 #define PTE_VALID		(_AT(pteval_t, 1) << 0)
 #define PTE_TYPE_MASK		(_AT(pteval_t, 3) << 0)
 #define PTE_TYPE_PAGE		(_AT(pteval_t, 3) << 0)
+#define PTE_TYPE_SECT		(_AT(pteval_t, 1) << 0)
 #define PTE_TABLE_BIT		(_AT(pteval_t, 1) << 1)
 #define PTE_USER		(_AT(pteval_t, 1) << 6)		/* AP[1] */
 #define PTE_RDONLY		(_AT(pteval_t, 1) << 7)		/* AP[2] */
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index c329ea061dc9..fa4c32a9f572 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -438,11 +438,6 @@ static inline void __set_ptes(struct mm_struct *mm,
 	}
 }
 
-/*
- * Huge pte definitions.
- */
-#define pte_mkhuge(pte)		(__pte(pte_val(pte) & ~PTE_TABLE_BIT))
-
 /*
  * Hugetlb definitions.
  */
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 5f1e2103888b..5922c95630ad 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -361,7 +361,7 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
 {
 	size_t pagesize = 1UL << shift;
 
-	entry = pte_mkhuge(entry);
+	entry = __pte((pte_val(entry) & ~PTE_TYPE_MASK) | PTE_TYPE_SECT);
 	if (pagesize == CONT_PTE_SIZE) {
 		entry = pte_mkcont(entry);
 	} else if (pagesize == CONT_PMD_SIZE) {
-- 
2.25.1

Re: [PATCH 1/5] arm64/mm: Drop pte_mkhuge()

Posted by Ryan Roberts 1 month, 2 weeks ago

On 05/10/2024 13:38, Anshuman Khandual wrote:
> Core HugeTLB defines arch_make_huge_pte() fallback definition, which calls
> platform provided pte_mkhuge(). But if any platform already provides custom
> arch_make_huge_pte(), then it does not need to provide pte_mkhuge(). arm64
> defines arch_make_huge_pte(), but then also calls pte_mkhuge() internally.
> This creates confusion as if both of these callbacks are being used in core
> HugeTLB and required to be defined in the platform.
> 
> This changes arch_make_huge_pte() to create block mapping directly and also
> drops off now redundant helper pte_mkhuge(), making things clear. Also this
> changes HugeTLB page creation from just clearing the PTE_TABLE_BIT (bit[1])
> to actually setting bits[1:0] via PTE_TYPE_[MASK|SECT] instead.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
>  arch/arm64/include/asm/pgtable-hwdef.h | 1 +
>  arch/arm64/include/asm/pgtable.h       | 5 -----
>  arch/arm64/mm/hugetlbpage.c            | 2 +-
>  3 files changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
> index fd330c1db289..956a702cb532 100644
> --- a/arch/arm64/include/asm/pgtable-hwdef.h
> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
> @@ -158,6 +158,7 @@
>  #define PTE_VALID		(_AT(pteval_t, 1) << 0)
>  #define PTE_TYPE_MASK		(_AT(pteval_t, 3) << 0)
>  #define PTE_TYPE_PAGE		(_AT(pteval_t, 3) << 0)
> +#define PTE_TYPE_SECT		(_AT(pteval_t, 1) << 0)
>  #define PTE_TABLE_BIT		(_AT(pteval_t, 1) << 1)
>  #define PTE_USER		(_AT(pteval_t, 1) << 6)		/* AP[1] */
>  #define PTE_RDONLY		(_AT(pteval_t, 1) << 7)		/* AP[2] */
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index c329ea061dc9..fa4c32a9f572 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -438,11 +438,6 @@ static inline void __set_ptes(struct mm_struct *mm,
>  	}
>  }
>  
> -/*
> - * Huge pte definitions.
> - */
> -#define pte_mkhuge(pte)		(__pte(pte_val(pte) & ~PTE_TABLE_BIT))
> -
>  /*
>   * Hugetlb definitions.
>   */
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 5f1e2103888b..5922c95630ad 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -361,7 +361,7 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
>  {
>  	size_t pagesize = 1UL << shift;
>  
> -	entry = pte_mkhuge(entry);
> +	entry = __pte((pte_val(entry) & ~PTE_TYPE_MASK) | PTE_TYPE_SECT);

I think there may be an existing bug here; if pagesize == CONT_PTE_SIZE, then
entry will be placed in the level 3 table. In this case, shouldn't bit 1 remain
set, because at level 3, a page mapping is denoted by bits[1:0] = 3 ? Currently
its being unconditionally cleared.

>  	if (pagesize == CONT_PTE_SIZE) {
>  		entry = pte_mkcont(entry);
>  	} else if (pagesize == CONT_PMD_SIZE) {

Re: [PATCH 1/5] arm64/mm: Drop pte_mkhuge()

Posted by Anshuman Khandual 1 month, 2 weeks ago


On 10/9/24 18:50, Ryan Roberts wrote:
> On 05/10/2024 13:38, Anshuman Khandual wrote:
>> Core HugeTLB defines arch_make_huge_pte() fallback definition, which calls
>> platform provided pte_mkhuge(). But if any platform already provides custom
>> arch_make_huge_pte(), then it does not need to provide pte_mkhuge(). arm64
>> defines arch_make_huge_pte(), but then also calls pte_mkhuge() internally.
>> This creates confusion as if both of these callbacks are being used in core
>> HugeTLB and required to be defined in the platform.
>>
>> This changes arch_make_huge_pte() to create block mapping directly and also
>> drops off now redundant helper pte_mkhuge(), making things clear. Also this
>> changes HugeTLB page creation from just clearing the PTE_TABLE_BIT (bit[1])
>> to actually setting bits[1:0] via PTE_TYPE_[MASK|SECT] instead.
>>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Will Deacon <will@kernel.org>
>> Cc: Ard Biesheuvel <ardb@kernel.org>
>> Cc: Ryan Roberts <ryan.roberts@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>>  arch/arm64/include/asm/pgtable-hwdef.h | 1 +
>>  arch/arm64/include/asm/pgtable.h       | 5 -----
>>  arch/arm64/mm/hugetlbpage.c            | 2 +-
>>  3 files changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
>> index fd330c1db289..956a702cb532 100644
>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>> @@ -158,6 +158,7 @@
>>  #define PTE_VALID		(_AT(pteval_t, 1) << 0)
>>  #define PTE_TYPE_MASK		(_AT(pteval_t, 3) << 0)
>>  #define PTE_TYPE_PAGE		(_AT(pteval_t, 3) << 0)
>> +#define PTE_TYPE_SECT		(_AT(pteval_t, 1) << 0)
>>  #define PTE_TABLE_BIT		(_AT(pteval_t, 1) << 1)
>>  #define PTE_USER		(_AT(pteval_t, 1) << 6)		/* AP[1] */
>>  #define PTE_RDONLY		(_AT(pteval_t, 1) << 7)		/* AP[2] */
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index c329ea061dc9..fa4c32a9f572 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -438,11 +438,6 @@ static inline void __set_ptes(struct mm_struct *mm,
>>  	}
>>  }
>>  
>> -/*
>> - * Huge pte definitions.
>> - */
>> -#define pte_mkhuge(pte)		(__pte(pte_val(pte) & ~PTE_TABLE_BIT))
>> -
>>  /*
>>   * Hugetlb definitions.
>>   */
>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>> index 5f1e2103888b..5922c95630ad 100644
>> --- a/arch/arm64/mm/hugetlbpage.c
>> +++ b/arch/arm64/mm/hugetlbpage.c
>> @@ -361,7 +361,7 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
>>  {
>>  	size_t pagesize = 1UL << shift;
>>  
>> -	entry = pte_mkhuge(entry);
>> +	entry = __pte((pte_val(entry) & ~PTE_TYPE_MASK) | PTE_TYPE_SECT);
> 
> I think there may be an existing bug here; if pagesize == CONT_PTE_SIZE, then
> entry will be placed in the level 3 table. In this case, shouldn't bit 1 remain
> set, because at level 3, a page mapping is denoted by bits[1:0] = 3 ? Currently
> its being unconditionally cleared.

That's not a problem, pte_mkcont() brings back both the bits
via PTE_TYPE_PAGE along with PTE_CONT.

        if (pagesize == CONT_PTE_SIZE) {
                entry = pte_mkcont(entry);
        } else if (pagesize == CONT_PMD_SIZE) {
                entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
        } else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
                pr_warn("%s: unrecognized huge page size 0x%lx\n",
                        __func__, pagesize);
        }

static inline pte_t pte_mkcont(pte_t pte)
{
	pte = set_pte_bit(pte, __pgprot(PTE_CONT));
      	return set_pte_bit(pte, __pgprot(PTE_TYPE_PAGE));
}

Although the same is not required for CONT_PMD_SIZE size huge
pages where only PTE_CONT is enough.

static inline pmd_t pmd_mkcont(pmd_t pmd)
{
        return __pmd(pmd_val(pmd) | PMD_SECT_CONT);
}
 
>>  	if (pagesize == CONT_PTE_SIZE) {
>>  		entry = pte_mkcont(entry);
>>  	} else if (pagesize == CONT_PMD_SIZE) {
>

Re: [PATCH 1/5] arm64/mm: Drop pte_mkhuge()

Posted by Ryan Roberts 1 month, 2 weeks ago

On 14/10/2024 09:59, Anshuman Khandual wrote:
> 
> 
> On 10/9/24 18:50, Ryan Roberts wrote:
>> On 05/10/2024 13:38, Anshuman Khandual wrote:
>>> Core HugeTLB defines arch_make_huge_pte() fallback definition, which calls
>>> platform provided pte_mkhuge(). But if any platform already provides custom
>>> arch_make_huge_pte(), then it does not need to provide pte_mkhuge(). arm64
>>> defines arch_make_huge_pte(), but then also calls pte_mkhuge() internally.
>>> This creates confusion as if both of these callbacks are being used in core
>>> HugeTLB and required to be defined in the platform.
>>>
>>> This changes arch_make_huge_pte() to create block mapping directly and also
>>> drops off now redundant helper pte_mkhuge(), making things clear. Also this
>>> changes HugeTLB page creation from just clearing the PTE_TABLE_BIT (bit[1])
>>> to actually setting bits[1:0] via PTE_TYPE_[MASK|SECT] instead.
>>>
>>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>>> Cc: Will Deacon <will@kernel.org>
>>> Cc: Ard Biesheuvel <ardb@kernel.org>
>>> Cc: Ryan Roberts <ryan.roberts@arm.com>
>>> Cc: Mark Rutland <mark.rutland@arm.com>
>>> Cc: linux-arm-kernel@lists.infradead.org
>>> Cc: linux-kernel@vger.kernel.org
>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>>> ---
>>>  arch/arm64/include/asm/pgtable-hwdef.h | 1 +
>>>  arch/arm64/include/asm/pgtable.h       | 5 -----
>>>  arch/arm64/mm/hugetlbpage.c            | 2 +-
>>>  3 files changed, 2 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
>>> index fd330c1db289..956a702cb532 100644
>>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>>> @@ -158,6 +158,7 @@
>>>  #define PTE_VALID		(_AT(pteval_t, 1) << 0)
>>>  #define PTE_TYPE_MASK		(_AT(pteval_t, 3) << 0)
>>>  #define PTE_TYPE_PAGE		(_AT(pteval_t, 3) << 0)
>>> +#define PTE_TYPE_SECT		(_AT(pteval_t, 1) << 0)
>>>  #define PTE_TABLE_BIT		(_AT(pteval_t, 1) << 1)
>>>  #define PTE_USER		(_AT(pteval_t, 1) << 6)		/* AP[1] */
>>>  #define PTE_RDONLY		(_AT(pteval_t, 1) << 7)		/* AP[2] */
>>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>>> index c329ea061dc9..fa4c32a9f572 100644
>>> --- a/arch/arm64/include/asm/pgtable.h
>>> +++ b/arch/arm64/include/asm/pgtable.h
>>> @@ -438,11 +438,6 @@ static inline void __set_ptes(struct mm_struct *mm,
>>>  	}
>>>  }
>>>  
>>> -/*
>>> - * Huge pte definitions.
>>> - */
>>> -#define pte_mkhuge(pte)		(__pte(pte_val(pte) & ~PTE_TABLE_BIT))
>>> -
>>>  /*
>>>   * Hugetlb definitions.
>>>   */
>>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>>> index 5f1e2103888b..5922c95630ad 100644
>>> --- a/arch/arm64/mm/hugetlbpage.c
>>> +++ b/arch/arm64/mm/hugetlbpage.c
>>> @@ -361,7 +361,7 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
>>>  {
>>>  	size_t pagesize = 1UL << shift;
>>>  
>>> -	entry = pte_mkhuge(entry);
>>> +	entry = __pte((pte_val(entry) & ~PTE_TYPE_MASK) | PTE_TYPE_SECT);
>>
>> I think there may be an existing bug here; if pagesize == CONT_PTE_SIZE, then
>> entry will be placed in the level 3 table. In this case, shouldn't bit 1 remain
>> set, because at level 3, a page mapping is denoted by bits[1:0] = 3 ? Currently
>> its being unconditionally cleared.
> 
> That's not a problem, pte_mkcont() brings back both the bits
> via PTE_TYPE_PAGE along with PTE_CONT.
> 
>         if (pagesize == CONT_PTE_SIZE) {
>                 entry = pte_mkcont(entry);
>         } else if (pagesize == CONT_PMD_SIZE) {
>                 entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
>         } else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
>                 pr_warn("%s: unrecognized huge page size 0x%lx\n",
>                         __func__, pagesize);
>         }
> 
> static inline pte_t pte_mkcont(pte_t pte)
> {
> 	pte = set_pte_bit(pte, __pgprot(PTE_CONT));
>       	return set_pte_bit(pte, __pgprot(PTE_TYPE_PAGE));

Oh wow, that's pretty hacky. Good job we never call pte_mkcont() on a
PTE_PRESENT_INVALID PTE. This would turn it valid again.

> }
> 
> Although the same is not required for CONT_PMD_SIZE size huge
> pages where only PTE_CONT is enough.
> 
> static inline pmd_t pmd_mkcont(pmd_t pmd)
> {
>         return __pmd(pmd_val(pmd) | PMD_SECT_CONT);
> }
>  
>>>  	if (pagesize == CONT_PTE_SIZE) {
>>>  		entry = pte_mkcont(entry);
>>>  	} else if (pagesize == CONT_PMD_SIZE) {
>>

Re: [PATCH 1/5] arm64/mm: Drop pte_mkhuge()

Posted by Anshuman Khandual 1 month, 1 week ago


On 10/14/24 16:38, Ryan Roberts wrote:
> On 14/10/2024 09:59, Anshuman Khandual wrote:
>>
>>
>> On 10/9/24 18:50, Ryan Roberts wrote:
>>> On 05/10/2024 13:38, Anshuman Khandual wrote:
>>>> Core HugeTLB defines arch_make_huge_pte() fallback definition, which calls
>>>> platform provided pte_mkhuge(). But if any platform already provides custom
>>>> arch_make_huge_pte(), then it does not need to provide pte_mkhuge(). arm64
>>>> defines arch_make_huge_pte(), but then also calls pte_mkhuge() internally.
>>>> This creates confusion as if both of these callbacks are being used in core
>>>> HugeTLB and required to be defined in the platform.
>>>>
>>>> This changes arch_make_huge_pte() to create block mapping directly and also
>>>> drops off now redundant helper pte_mkhuge(), making things clear. Also this
>>>> changes HugeTLB page creation from just clearing the PTE_TABLE_BIT (bit[1])
>>>> to actually setting bits[1:0] via PTE_TYPE_[MASK|SECT] instead.
>>>>
>>>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>>>> Cc: Will Deacon <will@kernel.org>
>>>> Cc: Ard Biesheuvel <ardb@kernel.org>
>>>> Cc: Ryan Roberts <ryan.roberts@arm.com>
>>>> Cc: Mark Rutland <mark.rutland@arm.com>
>>>> Cc: linux-arm-kernel@lists.infradead.org
>>>> Cc: linux-kernel@vger.kernel.org
>>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>>>> ---
>>>>  arch/arm64/include/asm/pgtable-hwdef.h | 1 +
>>>>  arch/arm64/include/asm/pgtable.h       | 5 -----
>>>>  arch/arm64/mm/hugetlbpage.c            | 2 +-
>>>>  3 files changed, 2 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
>>>> index fd330c1db289..956a702cb532 100644
>>>> --- a/arch/arm64/include/asm/pgtable-hwdef.h
>>>> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
>>>> @@ -158,6 +158,7 @@
>>>>  #define PTE_VALID		(_AT(pteval_t, 1) << 0)
>>>>  #define PTE_TYPE_MASK		(_AT(pteval_t, 3) << 0)
>>>>  #define PTE_TYPE_PAGE		(_AT(pteval_t, 3) << 0)
>>>> +#define PTE_TYPE_SECT		(_AT(pteval_t, 1) << 0)
>>>>  #define PTE_TABLE_BIT		(_AT(pteval_t, 1) << 1)
>>>>  #define PTE_USER		(_AT(pteval_t, 1) << 6)		/* AP[1] */
>>>>  #define PTE_RDONLY		(_AT(pteval_t, 1) << 7)		/* AP[2] */
>>>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>>>> index c329ea061dc9..fa4c32a9f572 100644
>>>> --- a/arch/arm64/include/asm/pgtable.h
>>>> +++ b/arch/arm64/include/asm/pgtable.h
>>>> @@ -438,11 +438,6 @@ static inline void __set_ptes(struct mm_struct *mm,
>>>>  	}
>>>>  }
>>>>  
>>>> -/*
>>>> - * Huge pte definitions.
>>>> - */
>>>> -#define pte_mkhuge(pte)		(__pte(pte_val(pte) & ~PTE_TABLE_BIT))
>>>> -
>>>>  /*
>>>>   * Hugetlb definitions.
>>>>   */
>>>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>>>> index 5f1e2103888b..5922c95630ad 100644
>>>> --- a/arch/arm64/mm/hugetlbpage.c
>>>> +++ b/arch/arm64/mm/hugetlbpage.c
>>>> @@ -361,7 +361,7 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
>>>>  {
>>>>  	size_t pagesize = 1UL << shift;
>>>>  
>>>> -	entry = pte_mkhuge(entry);
>>>> +	entry = __pte((pte_val(entry) & ~PTE_TYPE_MASK) | PTE_TYPE_SECT);
>>>
>>> I think there may be an existing bug here; if pagesize == CONT_PTE_SIZE, then
>>> entry will be placed in the level 3 table. In this case, shouldn't bit 1 remain
>>> set, because at level 3, a page mapping is denoted by bits[1:0] = 3 ? Currently
>>> its being unconditionally cleared.
>>
>> That's not a problem, pte_mkcont() brings back both the bits
>> via PTE_TYPE_PAGE along with PTE_CONT.
>>
>>         if (pagesize == CONT_PTE_SIZE) {
>>                 entry = pte_mkcont(entry);
>>         } else if (pagesize == CONT_PMD_SIZE) {
>>                 entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
>>         } else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
>>                 pr_warn("%s: unrecognized huge page size 0x%lx\n",
>>                         __func__, pagesize);
>>         }
>>
>> static inline pte_t pte_mkcont(pte_t pte)
>> {
>> 	pte = set_pte_bit(pte, __pgprot(PTE_CONT));
>>       	return set_pte_bit(pte, __pgprot(PTE_TYPE_PAGE));
> 
> Oh wow, that's pretty hacky. Good job we never call pte_mkcont() on a
> PTE_PRESENT_INVALID PTE. This would turn it valid again.

Ideally each individual HW page table helper should not do more than one thing
at a time. Here pte_mkcont() should just take a pte which is already a valid
one with PTE_TYPE_PAGE and just set PTE_CONT.

> 
>> }
>>
>> Although the same is not required for CONT_PMD_SIZE size huge
>> pages where only PTE_CONT is enough.
>>
>> static inline pmd_t pmd_mkcont(pmd_t pmd)
>> {
>>         return __pmd(pmd_val(pmd) | PMD_SECT_CONT);
>> }
>>  
>>>>  	if (pagesize == CONT_PTE_SIZE) {
>>>>  		entry = pte_mkcont(entry);
>>>>  	} else if (pagesize == CONT_PMD_SIZE) {
>>>
>

[PATCH 1/5] arm64/mm: Drop pte_mkhuge()
[PATCH 2/5] arm64/mm: Replace PXD_TABLE_BIT with PXD_TYPE_[MASK|SECT]
[PATCH 3/5] arm64/ptdump: Test PMD_TYPE_MASK for block mapping
[PATCH 4/5] KVM: arm64: ptdump: Test PMD_TYPE_MASK for block mapping
[PATCH 5/5] arm64/mm: Drop PXD_TABLE_BIT