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

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 19 Aug 2020 19:15:41 +0530

"Aneesh Kumar K.V" <[email-masked]> 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;