Re: [PATCH V2] mm: Merge pte_mkhuge() call into arch_make_huge_pte()
From: Anshuman Khandual
Date: Wed Mar 01 2023 - 03:32:58 EST
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.marinas@xxxxxxx>
>> Cc: Will Deacon <will@xxxxxxxxxx>
>> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
>> Cc: Paul Mackerras <paulus@xxxxxxxxx>
>> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
>> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
>> Cc: sparclinux@xxxxxxxxxxxxxxx
>> Cc: linux-mm@xxxxxxxxx
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Reviewed-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
>> Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> 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.khandual@xxxxxxx/
>>
>> 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);