From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
linux-mm@kvack.org, akpm@linux-foundation.org
Cc: linuxppc-dev@lists.ozlabs.org,
Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH v2 07/13] mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an existing pte entry
Date: Thu, 20 Aug 2020 16:32:54 +0200 [thread overview]
Message-ID: <b21d1dbb-7439-d317-8516-94c80f333e92@csgroup.eu> (raw)
In-Reply-To: <20200819130107.478414-8-aneesh.kumar@linux.ibm.com>
Le 19/08/2020 à 15:01, Aneesh Kumar K.V a écrit :
> set_pte_at() should not be used to set a pte entry at locations that
> already holds a valid pte entry. Architectures like ppc64 don't do TLB
> invalidate in set_pte_at() and hence expect it to be used to set locations
> that are not a valid PTE.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
> mm/debug_vm_pgtable.c | 35 +++++++++++++++--------------------
> 1 file changed, 15 insertions(+), 20 deletions(-)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 76f4c713e5a3..9c7e2c9cfc76 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -74,15 +74,18 @@ static void __init pte_advanced_tests(struct mm_struct *mm,
> {
> pte_t pte = pfn_pte(pfn, prot);
>
> + /*
> + * Architectures optimize set_pte_at by avoiding TLB flush.
> + * This requires set_pte_at to be not used to update an
> + * existing pte entry. Clear pte before we do set_pte_at
> + */
> +
> pr_debug("Validating PTE advanced\n");
> pte = pfn_pte(pfn, prot);
> set_pte_at(mm, vaddr, ptep, pte);
> ptep_set_wrprotect(mm, vaddr, ptep);
> pte = ptep_get(ptep);
> WARN_ON(pte_write(pte));
> -
> - pte = pfn_pte(pfn, prot);
> - set_pte_at(mm, vaddr, ptep, pte);
> ptep_get_and_clear(mm, vaddr, ptep);
> pte = ptep_get(ptep);
> WARN_ON(!pte_none(pte));
> @@ -96,13 +99,11 @@ static void __init pte_advanced_tests(struct mm_struct *mm,
> ptep_set_access_flags(vma, vaddr, ptep, pte, 1);
> pte = ptep_get(ptep);
> WARN_ON(!(pte_write(pte) && pte_dirty(pte)));
> -
> - pte = pfn_pte(pfn, prot);
> - set_pte_at(mm, vaddr, ptep, pte);
> ptep_get_and_clear_full(mm, vaddr, ptep, 1);
> pte = ptep_get(ptep);
> WARN_ON(!pte_none(pte));
>
> + pte = pfn_pte(pfn, prot);
> pte = pte_mkyoung(pte);
> set_pte_at(mm, vaddr, ptep, pte);
> ptep_test_and_clear_young(vma, vaddr, ptep);
> @@ -164,9 +165,6 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
> pmdp_set_wrprotect(mm, vaddr, pmdp);
> pmd = READ_ONCE(*pmdp);
> WARN_ON(pmd_write(pmd));
> -
> - pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
> - set_pmd_at(mm, vaddr, pmdp, pmd);
> pmdp_huge_get_and_clear(mm, vaddr, pmdp);
> pmd = READ_ONCE(*pmdp);
> WARN_ON(!pmd_none(pmd));
> @@ -180,13 +178,11 @@ static void __init pmd_advanced_tests(struct mm_struct *mm,
> pmdp_set_access_flags(vma, vaddr, pmdp, pmd, 1);
> pmd = READ_ONCE(*pmdp);
> WARN_ON(!(pmd_write(pmd) && pmd_dirty(pmd)));
> -
> - pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
> - set_pmd_at(mm, vaddr, pmdp, pmd);
> pmdp_huge_get_and_clear_full(vma, vaddr, pmdp, 1);
> pmd = READ_ONCE(*pmdp);
> WARN_ON(!pmd_none(pmd));
>
> + pmd = pmd_mkhuge(pfn_pmd(pfn, prot));
> pmd = pmd_mkyoung(pmd);
> set_pmd_at(mm, vaddr, pmdp, pmd);
> pmdp_test_and_clear_young(vma, vaddr, pmdp);
> @@ -283,18 +279,10 @@ static void __init pud_advanced_tests(struct mm_struct *mm,
> WARN_ON(pud_write(pud));
>
> #ifndef __PAGETABLE_PMD_FOLDED
Same as below, once set_put_at() is gone, I don't think this #ifndef
__PAGETABLE_PMD_FOLDED is still need, should be possible to replace by
'if (mm_pmd_folded())'
> -
> - pud = pud_mkhuge(pfn_pud(pfn, prot));
> - set_pud_at(mm, vaddr, pudp, pud);
> pudp_huge_get_and_clear(mm, vaddr, pudp);
> pud = READ_ONCE(*pudp);
> WARN_ON(!pud_none(pud));
>
> - pud = pud_mkhuge(pfn_pud(pfn, prot));
> - set_pud_at(mm, vaddr, pudp, pud);
> - pudp_huge_get_and_clear_full(mm, vaddr, pudp, 1);
> - pud = READ_ONCE(*pudp);
> - WARN_ON(!pud_none(pud));
> #endif /* __PAGETABLE_PMD_FOLDED */
>
> pud = pud_mkhuge(pfn_pud(pfn, prot));
> @@ -307,6 +295,13 @@ static void __init pud_advanced_tests(struct mm_struct *mm,
> pud = READ_ONCE(*pudp);
> WARN_ON(!(pud_write(pud) && pud_dirty(pud)));
>
> +#ifndef __PAGETABLE_PMD_FOLDED
> + pudp_huge_get_and_clear_full(vma, vaddr, pudp, 1);
> + pud = READ_ONCE(*pudp);
> + WARN_ON(!pud_none(pud));
> +#endif /* __PAGETABLE_PMD_FOLDED */
pudp_huge_get_and_clear_full() and pud_none() are always defined, I
think this #ifndef can be replaced by an 'if (mm_pmd_folded())'
> +
> + pud = pud_mkhuge(pfn_pud(pfn, prot));
> pud = pud_mkyoung(pud);
> set_pud_at(mm, vaddr, pudp, pud);
> pudp_test_and_clear_young(vma, vaddr, pudp);
>
Christophe
next prev parent reply other threads:[~2020-08-20 14:33 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 13:00 [PATCH v2 00/13] mm/debug_vm_pgtable fixes Aneesh Kumar K.V
2020-08-19 13:00 ` [PATCH v2 01/13] powerpc/mm: Add DEBUG_VM WARN for pmd_clear Aneesh Kumar K.V
2020-08-19 13:00 ` [PATCH v2 02/13] powerpc/mm: Move setting pte specific flags to pfn_pte Aneesh Kumar K.V
2020-08-19 13:00 ` [PATCH v2 03/13] mm/debug_vm_pgtable/ppc64: Avoid setting top bits in radom value Aneesh Kumar K.V
2020-08-19 13:00 ` [PATCH v2 04/13] mm/debug_vm_pgtables/hugevmap: Use the arch helper to identify huge vmap support Aneesh Kumar K.V
2020-08-19 16:29 ` kernel test robot
2020-08-20 5:31 ` Aneesh Kumar K.V
2020-08-21 8:38 ` Anshuman Khandual
2020-08-19 13:00 ` [PATCH v2 05/13] mm/debug_vm_pgtable/savedwrite: Enable savedwrite test with CONFIG_NUMA_BALANCING Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 06/13] mm/debug_vm_pgtable/THP: Mark the pte entry huge before using set_pmd/pud_at Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 07/13] mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an existing pte entry Aneesh Kumar K.V
2020-08-20 14:32 ` Christophe Leroy [this message]
2020-08-21 7:14 ` Aneesh Kumar K.V
2020-08-21 8:20 ` Anshuman Khandual
2020-08-19 13:01 ` [PATCH v2 08/13] mm/debug_vm_pgtable/thp: Use page table depost/withdraw with THP Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 09/13] mm/debug_vm_pgtable/locks: Move non page table modifying test together Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 10/13] mm/debug_vm_pgtable/locks: Take correct page table lock Aneesh Kumar K.V
2020-08-21 8:03 ` Anshuman Khandual
2020-08-21 8:08 ` Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 11/13] mm/debug_vm_pgtable/pmd_clear: Don't use pmd/pud_clear on pte entries Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 12/13] mm/debug_vm_pgtable/hugetlb: Disable hugetlb test on ppc64 Aneesh Kumar K.V
2020-08-19 13:01 ` [PATCH v2 13/13] mm/debug_vm_pgtable: populate a pte entry before fetching it Aneesh Kumar K.V
2020-08-19 13:45 ` [PATCH v2 00/13] mm/debug_vm_pgtable fixes Aneesh Kumar K.V
2020-08-21 3:33 ` Anshuman Khandual
2020-08-21 4:20 ` Anshuman Khandual
2020-08-21 6:53 ` Aneesh Kumar K.V
2020-08-21 8:01 ` Anshuman Khandual
2020-08-21 8:10 ` Aneesh Kumar K.V
2020-08-21 8:50 ` Aneesh Kumar K.V
2020-08-21 9:09 ` Anshuman Khandual
2020-08-21 8:51 ` Anshuman Khandual
2020-09-01 8:03 ` Christophe Leroy
2020-09-01 9:11 ` Anshuman Khandual
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