On 3/1/23 12:26, Christophe Leroy wrote:
> Hi,
> 
> Le 03/02/2022 à 04:57, Anshuman Khandual a écrit :
>> Each call into pte_mkhuge() is invariably followed by arch_make_huge_pte().
>> Instead arch_make_huge_pte() can accommodate pte_mkhuge() at the beginning.
>> This updates generic fallback stub for arch_make_huge_pte() and available
>> platforms definitions. This makes huge pte creation much cleaner and easier
>> to follow.
> 
> I can't remember, what was the reason for not doing it in 
> remove_migration_pte() as well ?
> Looking at it, I have the feeling that we now have a redundant 
> pte_mkhuge() there.

I guess it just got missed out, but you are right, there seems to be a redundant
pte_mkhuge() in remove_migration_pte(), I will send out a patch dropping it off.

> 
> Also, could we get rid of the one in mm/debug_vm_pgtable.c ?

After this patch, arch_make_huge_pte() should be used instead in generic MM for
all cases. So you are suggesting arch_make_huge_pte() should be tested instead ?

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index c631ade3f1d2..15ee86034ddc 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -909,7 +909,7 @@ static void __init hugetlb_basic_tests(struct 
pgtable_debug_args *args)
 #ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB
        pte = pfn_pte(args->fixed_pmd_pfn, args->page_prot);
 
-       WARN_ON(!pte_huge(pte_mkhuge(pte)));
+       WARN_ON(!pte_huge(arch_make_huge_pte(pte)));
 #endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
 }
 #else  /* !CONFIG_HUGETLB_PAGE */

> 
> Also, shouldn't arch_make_huge_pte() be documented in 
> Documentation/vm/arch_pgtable_helpers.rst instead of pte_mkhuge() ?

diff --git a/Documentation/mm/arch_pgtable_helpers.rst 
b/Documentation/mm/arch_pgtable_helpers.rst
index fd2a19df884e..07a0618f84de 100644
--- a/Documentation/mm/arch_pgtable_helpers.rst
+++ b/Documentation/mm/arch_pgtable_helpers.rst
@@ -216,7 +216,7 @@ HugeTLB Page Table Helpers
 
+---------------------------+--------------------------------------------------+
 | pte_huge                  | Tests a HugeTLB                                  
|
 
+---------------------------+--------------------------------------------------+
-| pte_mkhuge                | Creates a HugeTLB                                
|
+| arch_make_huge_pte        | Creates a HugeTLB                                
|
 
+---------------------------+--------------------------------------------------+
 | huge_pte_dirty            | Tests a dirty HugeTLB                            
|
 
+---------------------------+--------------------------------------------------+

I will send out a patch implementing the above changes. I guess pte_mkhuge() now
will just be a platform helper, which can be folded into arch_make_huge_pte() if
and when required.

- Anshuman

> 
> Christophe
> 
>>
>> Cc: Catalin Marinas <catalin.mari...@arm.com>
>> Cc: Will Deacon <w...@kernel.org>
>> Cc: Michael Ellerman <m...@ellerman.id.au>
>> Cc: Paul Mackerras <pau...@samba.org>
>> Cc: "David S. Miller" <da...@davemloft.net>
>> Cc: Mike Kravetz <mike.krav...@oracle.com>
>> Cc: Andrew Morton <a...@linux-foundation.org>
>> Cc: linux-arm-ker...@lists.infradead.org
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Cc: sparcli...@vger.kernel.org
>> Cc: linux...@kvack.org
>> Cc: linux-ker...@vger.kernel.org
>> Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu>
>> Acked-by: Mike Kravetz <mike.krav...@oracle.com>
>> Signed-off-by: Anshuman Khandual <anshuman.khand...@arm.com>
>> ---
>> This applies on v5.17-rc2
>>
>> Changes in V2:
>>
>> - Direct PTE encode in arch_make_huge_pte() on powerpc platform per 
>> Christophe
>>
>> Changes in V1:
>>
>> https://lore.kernel.org/all/1643780286-18798-1-git-send-email-anshuman.khand...@arm.com/
>>
>>   arch/arm64/mm/hugetlbpage.c                      | 1 +
>>   arch/powerpc/include/asm/nohash/32/hugetlb-8xx.h | 4 ++--
>>   arch/sparc/mm/hugetlbpage.c                      | 1 +
>>   include/linux/hugetlb.h                          | 2 +-
>>   mm/hugetlb.c                                     | 3 +--
>>   mm/vmalloc.c                                     | 1 -
>>   6 files changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>> index ffb9c229610a..228226c5fa80 100644
>> --- a/arch/arm64/mm/hugetlbpage.c
>> +++ b/arch/arm64/mm/hugetlbpage.c
>> @@ -347,6 +347,7 @@ 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);
>>      if (pagesize == CONT_PTE_SIZE) {
>>              entry = pte_mkcont(entry);
>>      } else if (pagesize == CONT_PMD_SIZE) {
>> diff --git a/arch/powerpc/include/asm/nohash/32/hugetlb-8xx.h 
>> b/arch/powerpc/include/asm/nohash/32/hugetlb-8xx.h
>> index 64b6c608eca4..de092b04ee1a 100644
>> --- a/arch/powerpc/include/asm/nohash/32/hugetlb-8xx.h
>> +++ b/arch/powerpc/include/asm/nohash/32/hugetlb-8xx.h
>> @@ -71,9 +71,9 @@ static inline pte_t arch_make_huge_pte(pte_t entry, 
>> unsigned int shift, vm_flags
>>      size_t size = 1UL << shift;
>>   
>>      if (size == SZ_16K)
>> -            return __pte(pte_val(entry) & ~_PAGE_HUGE);
>> +            return __pte(pte_val(entry) | _PAGE_SPS);
>>      else
>> -            return entry;
>> +            return __pte(pte_val(entry) | _PAGE_SPS | _PAGE_HUGE);
>>   }
>>   #define arch_make_huge_pte arch_make_huge_pte
>>   #endif
>> diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
>> index 0f49fada2093..d8e0e3c7038d 100644
>> --- a/arch/sparc/mm/hugetlbpage.c
>> +++ b/arch/sparc/mm/hugetlbpage.c
>> @@ -181,6 +181,7 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int 
>> shift, vm_flags_t flags)
>>   {
>>      pte_t pte;
>>   
>> +    entry = pte_mkhuge(entry);
>>      pte = hugepage_shift_to_tte(entry, shift);
>>   
>>   #ifdef CONFIG_SPARC64
>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>> index d1897a69c540..52c462390aee 100644
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
>> @@ -754,7 +754,7 @@ static inline void arch_clear_hugepage_flags(struct page 
>> *page) { }
>>   static inline pte_t arch_make_huge_pte(pte_t entry, unsigned int shift,
>>                                     vm_flags_t flags)
>>   {
>> -    return entry;
>> +    return pte_mkhuge(entry);
>>   }
>>   #endif
>>   
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 61895cc01d09..5ca253c1b4e4 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -4637,7 +4637,6 @@ static pte_t make_huge_pte(struct vm_area_struct *vma, 
>> struct page *page,
>>                                         vma->vm_page_prot));
>>      }
>>      entry = pte_mkyoung(entry);
>> -    entry = pte_mkhuge(entry);
>>      entry = arch_make_huge_pte(entry, shift, vma->vm_flags);
>>   
>>      return entry;
>> @@ -6172,7 +6171,7 @@ unsigned long hugetlb_change_protection(struct 
>> vm_area_struct *vma,
>>                      unsigned int shift = huge_page_shift(hstate_vma(vma));
>>   
>>                      old_pte = huge_ptep_modify_prot_start(vma, address, 
>> ptep);
>> -                    pte = pte_mkhuge(huge_pte_modify(old_pte, newprot));
>> +                    pte = huge_pte_modify(old_pte, newprot);
>>                      pte = arch_make_huge_pte(pte, shift, vma->vm_flags);
>>                      huge_ptep_modify_prot_commit(vma, address, ptep, 
>> old_pte, pte);
>>                      pages++;
>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
>> index 4165304d3547..d0b14dd73adc 100644
>> --- a/mm/vmalloc.c
>> +++ b/mm/vmalloc.c
>> @@ -118,7 +118,6 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long 
>> addr, unsigned long end,
>>              if (size != PAGE_SIZE) {
>>                      pte_t entry = pfn_pte(pfn, prot);
>>   
>> -                    entry = pte_mkhuge(entry);
>>                      entry = arch_make_huge_pte(entry, ilog2(size), 0);
>>                      set_huge_pte_at(&init_mm, addr, pte, entry);
>>                      pfn += PFN_DOWN(size);

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