Re: [PATCH v2 00/13] mm/debug_vm_pgtable fixes

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

On 8/21/20 9:03 AM, Anshuman Khandual wrote:
> 
> 
> On 08/19/2020 07:15 PM, Aneesh Kumar K.V wrote:
>> "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> writes:
>>
>>> This patch series includes fixes for debug_vm_pgtable test code so that
>>> they follow page table updates rules correctly. The first two patches introduce
>>> changes w.r.t ppc64. The patches are included in this series for completeness. We can
>>> merge them via ppc64 tree if required.
>>>
>>> Hugetlb test is disabled on ppc64 because that needs larger change to satisfy
>>> page table update rules.
>>>
>>> Changes from V1:
>>> * Address review feedback
>>> * drop test specific pfn_pte and pfn_pmd.
>>> * Update ppc64 page table helper to add _PAGE_PTE
>>>
>>> Aneesh Kumar K.V (13):
>>>    powerpc/mm: Add DEBUG_VM WARN for pmd_clear
>>>    powerpc/mm: Move setting pte specific flags to pfn_pte
>>>    mm/debug_vm_pgtable/ppc64: Avoid setting top bits in radom value
>>>    mm/debug_vm_pgtables/hugevmap: Use the arch helper to identify huge
>>>      vmap support.
>>>    mm/debug_vm_pgtable/savedwrite: Enable savedwrite test with
>>>      CONFIG_NUMA_BALANCING
>>>    mm/debug_vm_pgtable/THP: Mark the pte entry huge before using
>>>      set_pmd/pud_at
>>>    mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an
>>>      existing pte entry
>>>    mm/debug_vm_pgtable/thp: Use page table depost/withdraw with THP
>>>    mm/debug_vm_pgtable/locks: Move non page table modifying test together
>>>    mm/debug_vm_pgtable/locks: Take correct page table lock
>>>    mm/debug_vm_pgtable/pmd_clear: Don't use pmd/pud_clear on pte entries
>>>    mm/debug_vm_pgtable/hugetlb: Disable hugetlb test on ppc64
>>>    mm/debug_vm_pgtable: populate a pte entry before fetching it
>>>
>>>   arch/powerpc/include/asm/book3s/64/pgtable.h |  29 +++-
>>>   arch/powerpc/include/asm/nohash/pgtable.h    |   5 -
>>>   arch/powerpc/mm/book3s64/pgtable.c           |   2 +-
>>>   arch/powerpc/mm/pgtable.c                    |   5 -
>>>   include/linux/io.h                           |  12 ++
>>>   mm/debug_vm_pgtable.c                        | 151 +++++++++++--------
>>>   6 files changed, 127 insertions(+), 77 deletions(-)
>>>
>>
>> BTW I picked a wrong branch when sending this. Attaching the diff
>> against what I want to send.  pfn_pmd() no more updates _PAGE_PTE
>> because that is handled by pmd_mkhuge().
>>
>> diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
>> index 3b4da7c63e28..e18ae50a275c 100644
>> --- a/arch/powerpc/mm/book3s64/pgtable.c
>> +++ b/arch/powerpc/mm/book3s64/pgtable.c
>> @@ -141,7 +141,7 @@ pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
>>   	unsigned long pmdv;
>>   
>>   	pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK;
>> -	return __pmd(pmdv | pgprot_val(pgprot) | _PAGE_PTE);
>> +	return pmd_set_protbits(__pmd(pmdv), pgprot);
>>   }
>>   
>>   pmd_t mk_pmd(struct page *page, pgprot_t pgprot)
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 7d9f8e1d790f..cad61d22f33a 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -229,7 +229,7 @@ static void __init pmd_huge_tests(pmd_t *pmdp, unsigned long pfn, pgprot_t prot)
>>   
>>   static void __init pmd_savedwrite_tests(unsigned long pfn, pgprot_t prot)
>>   {
>> -	pmd_t pmd = pfn_pmd(pfn, prot);
>> +	pmd_t pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
>>   
>>   	if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
>>   		return;
>>
> 
> Cover letter does not mention which branch or tag this series applies on.
> Just assumed it to be 5.9-rc1. Should the above changes be captured as a
> pre-requisite patch ?
> 
> Anyways, the series fails to be build on arm64.
> 
> A) Without CONFIG_TRANSPARENT_HUGEPAGE
> 
> mm/debug_vm_pgtable.c: In function ‘debug_vm_pgtable’:
> mm/debug_vm_pgtable.c:1045:2: error: too many arguments to function ‘pmd_advanced_tests’
>    pmd_advanced_tests(mm, vma, pmdp, pmd_aligned, vaddr, prot, saved_ptep);
>    ^~~~~~~~~~~~~~~~~~
> mm/debug_vm_pgtable.c:366:20: note: declared here
>   static void __init pmd_advanced_tests(struct mm_struct *mm,
>                      ^~~~~~~~~~~~~~~~~~
> 
> B) As mentioned previously, this should be solved by including <linux/io.h>
> 
> mm/debug_vm_pgtable.c: In function ‘pmd_huge_tests’:
> mm/debug_vm_pgtable.c:215:7: error: implicit declaration of function ‘arch_ioremap_pmd_supported’; did you mean ‘arch_disable_smp_support’? [-Werror=implicit-function-declaration]
>    if (!arch_ioremap_pmd_supported())
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Please make sure that the series builds on all enabled platforms i.e x86,
> arm64, ppc32, ppc64, arc, s390 along with selectively enabling/disabling
> all the features that make various #ifdefs in the test.
> 

I was hoping to get kernel test robot build report to verify that. But 
if you can help with that i have pushed a branch to github with reported 
build failure fixes.

https://github.com/kvaneesh/linux/tree/debug_vm_pgtable

I still haven't looked at the PMD_FOLDED feedback from Christophe 
because I am not sure i follow why we are checking for PMD folded there.

-aneesh