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Date: Thu, 22 Jul 2021 11:26:52 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Gavin Shan <gshan@...hat.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
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.
>
> 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.
> +
> + 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.
> +
> + pte = pfn_pte(args->pte_pfn, args->page_prot);
Please keep this unchanged and move to its original position.
> #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.
> 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))
>
> 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.
>
> ptl = pmd_lock(mm, pmdp);
> pmd_clear_tests(mm, pmdp);
>
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