[PATCH v3 08/13] mm/debug_vm_pgtable/thp: Use page table depost/withdraw with THP

[Aneesh Kumar K.V]

On 9/1/20 8:52 AM, Anshuman Khandual wrote:
> 
> 
> On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
>> Architectures like ppc64 use deposited page table while updating the huge pte
>> entries.
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
>> ---
>>   mm/debug_vm_pgtable.c | 10 +++++++---
>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index f9f6358899a8..0ce5c6a24c5b 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -154,7 +154,7 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot)
>>   static void __init pmd_advanced_tests(struct mm_struct *mm,
>>   				      struct vm_area_struct *vma, pmd_t *pmdp,
>>   				      unsigned long pfn, unsigned long vaddr,
>> -				      pgprot_t prot)
>> +				      pgprot_t prot, pgtable_t pgtable)
>>   {
>>   	pmd_t pmd;
>>   
>> @@ -165,6 +165,8 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
>>   	/* Align the address wrt HPAGE_PMD_SIZE */
>>   	vaddr = (vaddr & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
>>   
>> +	pgtable_trans_huge_deposit(mm, pmdp, pgtable);
>> +
>>   	pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
>>   	set_pmd_at(mm, vaddr, pmdp, pmd);
>>   	pmdp_set_wrprotect(mm, vaddr, pmdp);
>> @@ -193,6 +195,8 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
>>   	pmdp_test_and_clear_young(vma, vaddr, pmdp);
>>   	pmd = READ_ONCE(*pmdp);
>>   	WARN_ON(pmd_young(pmd));
>> +
>> +	pgtable = pgtable_trans_huge_withdraw(mm, pmdp);
> 
> Should the call sites here be wrapped with __HAVE_ARCH_PGTABLE_DEPOSIT and
> __HAVE_ARCH_PGTABLE_WITHDRAW respectively. Though there are generic fallback
> definitions, wondering whether they are indeed essential for all platforms.
> 

No, because Any page table helpers operating on pmd level THP can expect 
a deposited page table.

__HAVE_ARCH_PGTABLE_DEPOSIT indicates that fallback to generic version.

>>   }
>>   
>>   static void __init pmd_leaf_tests(unsigned long pfn, pgprot_t prot)
>> @@ -373,7 +377,7 @@ static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) { }
>>   static void __init pmd_advanced_tests(struct mm_struct *mm,
>>   				      struct vm_area_struct *vma, pmd_t *pmdp,
>>   				      unsigned long pfn, unsigned long vaddr,
>> -				      pgprot_t prot)
>> +				      pgprot_t prot, pgtable_t pgtable)
>>   {
>>   }
>>   static void __init pud_advanced_tests(struct mm_struct *mm,
>> @@ -1015,7 +1019,7 @@ static int __init debug_vm_pgtable(void)
>>   	pgd_clear_tests(mm, pgdp);
>>   
>>   	pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
>> -	pmd_advanced_tests(mm, vma, pmdp, pmd_aligned, vaddr, prot);
>> +	pmd_advanced_tests(mm, vma, pmdp, pmd_aligned, vaddr, prot, saved_ptep);
>>   	pud_advanced_tests(mm, vma, pudp, pud_aligned, vaddr, prot);
>>   	hugetlb_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
>>   
>>
> 
> There is a checkpatch.pl warning here.
> 
> WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
> #7:
> Architectures like ppc64 use deposited page table while updating the huge pte
> 
> total: 0 errors, 1 warnings, 40 lines checked
> 

I will ignore all these, because they are not really important IMHO.

-aneesh