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Date: Thu, 22 Jul 2021 16:37:26 +1000 From: Gavin Shan <gshan@...hat.com> To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org Cc: linux-kernel@...r.kernel.org, catalin.marinas@....com, will@...nel.org, akpm@...ux-foundation.org, chuhu@...hat.com, shan.gavin@...il.com Subject: Re: [PATCH v3 07/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PTE modifying tests Hi Anshuman, On 7/22/21 3:56 PM, Anshuman Khandual wrote: > On 7/19/21 6:36 PM, Gavin Shan wrote: >> This uses struct pgtable_debug_args in PTE modifying tests. The allocated >> page is used as set_pte_at() is used there. The tests are skipped if >> the allocated page doesn't exist. Besides, the unused variable @ptep >> and @pte_aligned in debug_vm_pgtable() are dropped. > > Please dont drop @ptep and @pte_aligned just yet. > We need to do so. Otherwise, there are build warning raised to complain something like 'unused variable'. >> >> Signed-off-by: Gavin Shan <gshan@...hat.com> >> --- >> mm/debug_vm_pgtable.c | 75 ++++++++++++++++++++++--------------------- >> 1 file changed, 39 insertions(+), 36 deletions(-) >> >> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c >> index d32e55a95c55..eb6dda88e0d9 100644 >> --- a/mm/debug_vm_pgtable.c >> +++ b/mm/debug_vm_pgtable.c >> @@ -116,10 +116,7 @@ static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx) >> WARN_ON(!pte_dirty(pte_wrprotect(pte_mkdirty(pte)))); >> } >> >> -static void __init pte_advanced_tests(struct mm_struct *mm, >> - struct vm_area_struct *vma, pte_t *ptep, >> - unsigned long pfn, unsigned long vaddr, >> - pgprot_t prot) >> +static void __init pte_advanced_tests(struct pgtable_debug_args *args) >> { >> pte_t pte; >> >> @@ -130,33 +127,38 @@ static void __init pte_advanced_tests(struct mm_struct *mm, >> */ >> >> 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); >> + if (args->pte_pfn == ULONG_MAX) { >> + pr_debug("%s: Skipped\n", __func__); >> + return; >> + } > > Just return. Please dont call out "Skipped". Also this check should be > performed before printing pr_debug("Validating PTE advanced\n"). The > print indicates that the test has started. > Sure. >> + >> + pte = pfn_pte(args->pte_pfn, args->page_prot); >> + set_pte_at(args->mm, args->vaddr, args->ptep, pte); >> + ptep_set_wrprotect(args->mm, args->vaddr, args->ptep); >> + pte = ptep_get(args->ptep); >> WARN_ON(pte_write(pte)); >> - ptep_get_and_clear(mm, vaddr, ptep); >> - pte = ptep_get(ptep); >> + ptep_get_and_clear(args->mm, args->vaddr, args->ptep); >> + pte = ptep_get(args->ptep); >> WARN_ON(!pte_none(pte)); >> >> - pte = pfn_pte(pfn, prot); >> + pte = pfn_pte(args->pte_pfn, args->page_prot); >> pte = pte_wrprotect(pte); >> pte = pte_mkclean(pte); >> - set_pte_at(mm, vaddr, ptep, pte); >> + set_pte_at(args->mm, args->vaddr, args->ptep, pte); >> pte = pte_mkwrite(pte); >> pte = pte_mkdirty(pte); >> - ptep_set_access_flags(vma, vaddr, ptep, pte, 1); >> - pte = ptep_get(ptep); >> + ptep_set_access_flags(args->vma, args->vaddr, args->ptep, pte, 1); >> + pte = ptep_get(args->ptep); >> WARN_ON(!(pte_write(pte) && pte_dirty(pte))); >> - ptep_get_and_clear_full(mm, vaddr, ptep, 1); >> - pte = ptep_get(ptep); >> + ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1); >> + pte = ptep_get(args->ptep); >> WARN_ON(!pte_none(pte)); >> >> - pte = pfn_pte(pfn, prot); >> + pte = pfn_pte(args->pte_pfn, args->page_prot); >> pte = pte_mkyoung(pte); >> - set_pte_at(mm, vaddr, ptep, pte); >> - ptep_test_and_clear_young(vma, vaddr, ptep); >> - pte = ptep_get(ptep); >> + set_pte_at(args->mm, args->vaddr, args->ptep, pte); >> + ptep_test_and_clear_young(args->vma, args->vaddr, args->ptep); >> + pte = ptep_get(args->ptep); >> WARN_ON(pte_young(pte)); >> } >> >> @@ -617,20 +619,24 @@ static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp, >> } >> #endif /* PAGETABLE_P4D_FOLDED */ >> >> -static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep, >> - unsigned long pfn, unsigned long vaddr, >> - pgprot_t prot) >> +static void __init pte_clear_tests(struct pgtable_debug_args *args) >> { >> - pte_t pte = pfn_pte(pfn, prot); >> + pte_t pte; >> >> pr_debug("Validating PTE clear\n"); >> + if (args->pte_pfn == ULONG_MAX) { >> + pr_debug("%s: Skipped\n", __func__); >> + return; >> + } > > Just return. Please dont call out "Skipped". Also this check should be > performed before printing pr_debug("Validating PTE clear\n"). The print > indicates that the test has started. > Sure. >> + >> + pte = pfn_pte(args->pte_pfn, args->page_prot); > > Please keep this unchanged and move to its original position. > Ok. >> #ifndef CONFIG_RISCV >> pte = __pte(pte_val(pte) | RANDOM_ORVALUE); >> #endif >> - set_pte_at(mm, vaddr, ptep, pte); >> + set_pte_at(args->mm, args->vaddr, args->ptep, pte); >> barrier(); >> - pte_clear(mm, vaddr, ptep); >> - pte = ptep_get(ptep); >> + pte_clear(args->mm, args->vaddr, args->ptep); >> + pte = ptep_get(args->ptep); >> WARN_ON(!pte_none(pte)); >> } >> >> @@ -1150,11 +1156,10 @@ static int __init debug_vm_pgtable(void) >> p4d_t *p4dp, *saved_p4dp; >> pud_t *pudp, *saved_pudp; >> pmd_t *pmdp, *saved_pmdp, pmd; >> - pte_t *ptep; >> pgtable_t saved_ptep; >> pgprot_t prot; >> phys_addr_t paddr; >> - unsigned long vaddr, pte_aligned, pmd_aligned; >> + unsigned long vaddr, pmd_aligned; >> unsigned long pud_aligned; >> spinlock_t *ptl = NULL; >> int idx, ret; >> @@ -1189,10 +1194,8 @@ static int __init debug_vm_pgtable(void) >> */ >> paddr = __pa_symbol(&start_kernel); >> >> - pte_aligned = (paddr & PAGE_MASK) >> PAGE_SHIFT; > > Please dont drop pte_aligned just yet. > We need to drop the variable. Otherwise, there is build warning to complain: 'unused variable'. >> pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT; >> pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT; >> - WARN_ON(!pfn_valid(pte_aligned)); > > This should go into init_args() at the right place as the following, > after evaluating it from 'start_kernel' symbol - just to be sure. > > WARN_ON(!pfn_valid(args->fixed_pte_pfn)) > Yes. >> >> pgdp = pgd_offset(mm, vaddr); >> p4dp = p4d_alloc(mm, pgdp, vaddr); >> @@ -1272,11 +1275,11 @@ static int __init debug_vm_pgtable(void) >> * Page table modifying tests. They need to hold >> * proper page table lock. >> */ >> - >> - ptep = pte_offset_map_lock(mm, pmdp, vaddr, &ptl); >> - pte_clear_tests(mm, ptep, pte_aligned, vaddr, prot); >> - pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot); >> - pte_unmap_unlock(ptep, ptl); >> + ptl = pte_lockptr(args.mm, args.pmdp); >> + spin_lock(ptl); >> + pte_clear_tests(&args); >> + pte_advanced_tests(&args); >> + spin_unlock(ptl); > > Why pte_offset_map_lock()/pte_unmap_unlock() has been dropped and > spin_lock()/spin_unlock() sequence has been added ? Please dont > change the tests in these patches. > The semantics of pte_offset_map_lock() is to grab and take the lock and return the PTE entry, which is mapped if needed. We already had the PTE entry tracked by args->ptep in init_args(). So some of the operations covered by pte_offset_map_lock() isn't needed any more. >> >> ptl = pmd_lock(mm, pmdp); >> pmd_clear_tests(mm, pmdp); >> > Thanks, Gavin
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