Re: [PATCH v4 07/13] mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an existing pte entry
On 09/02/2020 05:12 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.
>
> Signed-off-by: Aneesh Kumar K.V
> ---
> 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 9cafed39c236..de333871f407 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -79,15 +79,18 @@ 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));
> @@ -101,13 +104,11 @@ 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);
> @@ -169,9 +170,6 @@ 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));
> @@ -185,13 +183,11 @@ 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);
> @@ -292,17 +288,9 @@ static void __init pud_advanced_tests(struct mm_struct
> *mm,
> WARN_ON(pud_write(pud));
>
> #ifndef __PAGETABLE_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));
> @@ -315,6 +303,13 @@ 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(mm, vaddr, pudp, 1);
> + pud = READ_ONCE(*pudp);
> + WARN_ON(!pud_none(pud));
> +#endif /* __PAGETABLE_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);
>
Reviewed-by: Anshuman Khandual
[PATCH v4 07/13] mm/debug_vm_pgtable/set_pte/pmd/pud: Don't use set_*_at to update an existing pte entry
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
---
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 9cafed39c236..de333871f407 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -79,15 +79,18 @@ 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));
@@ -101,13 +104,11 @@ 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);
@@ -169,9 +170,6 @@ 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));
@@ -185,13 +183,11 @@ 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);
@@ -292,17 +288,9 @@ static void __init pud_advanced_tests(struct mm_struct *mm,
WARN_ON(pud_write(pud));
#ifndef __PAGETABLE_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));
@@ -315,6 +303,13 @@ 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(mm, vaddr, pudp, 1);
+ pud = READ_ONCE(*pudp);
+ WARN_ON(!pud_none(pud));
+#endif /* __PAGETABLE_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);
--
2.26.2
