From: Anshuman Khandual <anshuman.khandual@arm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
linux-mm@kvack.org, akpm@linux-foundation.org
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 03/16] debug_vm_pgtable/set_pte: Don't use set_pte_at to update an existing pte entry
Date: Wed, 12 Aug 2020 14:42:31 +0530 [thread overview]
Message-ID: <94ed519a-2cf2-af50-82be-2a559dee7d86@arm.com> (raw)
In-Reply-To: <20200812063358.369514-3-aneesh.kumar@linux.ibm.com>
On 08/12/2020 12:03 PM, Aneesh Kumar K.V wrote:
> 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.
Even though set_pte_at() is not really a arch page table helper and
very much arch specific, I just wonder why this deviation on ppc64
as compared to other platforms. Detecting such semantics variation
across platforms is an objective of this test.
As small nit.
Please follow the existing subject format for all patches in here.
It will improve readability and also help understand these changes
better, later on.
mm/debug_vm_pgtable: <Specify changes to an individual test>
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
> mm/debug_vm_pgtable.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 4c32063a8acf..02a7c20aa4a2 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -81,8 +81,6 @@ static void __init pte_advanced_tests(struct mm_struct *mm,
> 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));
This makes sense. But could you please fold this code stanza with
the previous one in order to imply that 'ptep' did have some valid
entry before being cleared and checked against pte_none().
> @@ -97,12 +95,14 @@ static void __init pte_advanced_tests(struct mm_struct *mm,
> 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));
Same, please fold back.
>
> + /*
> + * We should clear pte before we do set_pte_at
> + */
> + pte = ptep_get_and_clear(mm, vaddr, ptep);
> pte = pte_mkyoung(pte);
> set_pte_at(mm, vaddr, ptep, pte);
> ptep_test_and_clear_young(vma, vaddr, ptep);
>
The comment above should also explain details that are mentioned
in the commit message i.e how platforms such as ppc64 expects a
clear pte entry for set_pte_at() to work.
next prev parent reply other threads:[~2020-08-12 9:15 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-12 6:33 [PATCH 01/16] powerpc/mm: Add DEBUG_VM WARN for pmd_clear Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 02/16] debug_vm_pgtable/ppc64: Avoid setting top bits in radom value Aneesh Kumar K.V
2020-08-12 6:40 ` Christophe Leroy
2020-08-12 6:43 ` Aneesh Kumar K.V
2020-08-12 8:12 ` Anshuman Khandual
2020-08-12 8:25 ` Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 03/16] debug_vm_pgtable/set_pte: Don't use set_pte_at to update an existing pte entry Aneesh Kumar K.V
2020-08-12 9:12 ` Anshuman Khandual [this message]
2020-08-12 9:22 ` Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 04/16] debug_vm_pgtables/hugevmap: Use the arch helper to identify huge vmap support Aneesh Kumar K.V
2020-08-12 10:30 ` Anshuman Khandual
2020-08-12 6:33 ` [PATCH 05/16] debug_vm_pgtable/savedwrite: Enable savedwrite test with CONFIG_NUMA_BALANCING Aneesh Kumar K.V
2020-08-12 11:24 ` Anshuman Khandual
2020-08-12 6:33 ` [PATCH 06/16] debug_vm_pgtable/THP: Mark the pte entry huge before using set_pmd_at Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 07/16] debug_vm_pgtable/THP: Mark the pte entry huge before using set_pud_at Aneesh Kumar K.V
2020-08-12 11:49 ` Anshuman Khandual
2020-08-12 6:33 ` [PATCH 08/16] debug_vm_pgtable/set_pmd: Don't use set_pmd_at to update an existing pmd entry Aneesh Kumar K.V
2020-08-12 12:46 ` Anshuman Khandual
2020-08-12 6:33 ` [PATCH 09/16] debug_vm_pgtable/set_pud: Don't use set_pud_at to update an existing pud entry Aneesh Kumar K.V
2020-08-12 12:46 ` Anshuman Khandual
2020-08-12 6:33 ` [PATCH 10/16] debug_vm_pgtable/thp: Use page table depost/withdraw with THP Aneesh Kumar K.V
2020-08-13 5:25 ` Anshuman Khandual
2020-08-13 6:38 ` Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 11/16] debug_vm_pgtable/locks: Move non page table modifying test together Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 12/16] debug_vm_pgtable/locks: Take correct page table lock Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 13/16] debug_vm_pgtable/pmd_clear: Don't use pmd/pud_clear on pte entries Aneesh Kumar K.V
2020-08-13 5:27 ` Anshuman Khandual
2020-08-13 8:45 ` Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 14/16] debug_vm_pgtable/hugetlb: Disable hugetlb test on ppc64 Aneesh Kumar K.V
2020-08-12 13:03 ` Anshuman Khandual
2020-08-12 13:16 ` Aneesh Kumar K.V
2020-08-12 13:34 ` Anshuman Khandual
2020-08-12 13:52 ` Aneesh Kumar K.V
2020-08-14 8:43 ` Anshuman Khandual
2020-08-19 6:54 ` Aneesh Kumar K.V
2020-08-12 6:33 ` [PATCH 15/16] debug_vm_pgtable/savedwrite: Use savedwrite test with protnone ptes Aneesh Kumar K.V
2020-08-12 13:06 ` Anshuman Khandual
2020-08-12 6:33 ` [PATCH 16/16] debug_vm_pgtable/ppc64: Add a variant of pfn_pte/pmd Aneesh Kumar K.V
2020-08-13 5:30 ` Anshuman Khandual
2020-08-13 6:37 ` Aneesh Kumar K.V
2020-08-14 8:29 ` Anshuman Khandual
2020-08-12 7:46 ` [PATCH 01/16] powerpc/mm: Add DEBUG_VM WARN for pmd_clear Anshuman Khandual
2020-08-12 8:27 ` Aneesh Kumar K.V
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