Messages in this thread |  | | Subject | Re: [PATCH 1/2] mm/debug_vm_pgtable/basic: Add validation for dirtiness after write protect | From | Christophe Leroy <> | Date | Fri, 27 Nov 2020 09:22:24 +0100 |
| |
Le 27/11/2020 à 06:06, Anshuman Khandual a écrit : > This adds validation tests for dirtiness after write protect conversion for > each page table level. This is important for platforms such as arm64 that > removes the hardware dirty bit while making it an write protected one. This > also fixes pxx_wrprotect() related typos in the documentation file. >
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index c05d9dcf7891..a5be11210597 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -70,6 +70,7 @@ static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot) > WARN_ON(pte_young(pte_mkold(pte_mkyoung(pte)))); > WARN_ON(pte_dirty(pte_mkclean(pte_mkdirty(pte)))); > WARN_ON(pte_write(pte_wrprotect(pte_mkwrite(pte)))); > + WARN_ON(pte_dirty(pte_wrprotect(pte)));
Wondering what you are testing here exactly.
Do you expect that if PTE has the dirty bit, it gets cleared by pte_wrprotect() ?
Powerpc doesn't do that, it only clears the RW bit but the dirty bit remains if it is set, until you call pte_mkclean() explicitely.
> } > > static void __init pte_advanced_tests(struct mm_struct *mm, > @@ -144,6 +145,7 @@ static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) > WARN_ON(pmd_young(pmd_mkold(pmd_mkyoung(pmd)))); > WARN_ON(pmd_dirty(pmd_mkclean(pmd_mkdirty(pmd)))); > WARN_ON(pmd_write(pmd_wrprotect(pmd_mkwrite(pmd)))); > + WARN_ON(pmd_dirty(pmd_wrprotect(pmd))); > /* > * A huge page does not point to next level page table > * entry. Hence this must qualify as pmd_bad(). > @@ -262,6 +264,7 @@ static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) > WARN_ON(!pud_write(pud_mkwrite(pud_wrprotect(pud)))); > WARN_ON(pud_write(pud_wrprotect(pud_mkwrite(pud)))); > WARN_ON(pud_young(pud_mkold(pud_mkyoung(pud)))); > + WARN_ON(pud_dirty(pud_wrprotect(pud))); > > if (mm_pmd_folded(mm)) > return; >
Christophe
|  |