Hi Anshuman,

On 7/22/21 3:56 PM, Anshuman Khandual wrote:

On 7/19/21 6:36 PM, Gavin Shan wrote:

quoted

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'.

quoted

Signed-off-by: Gavin Shan <redacted>
---
  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.

quoted

+
+	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.

quoted

+
+	pte = pfn_pte(args->pte_pfn, args->page_prot);

Please keep this unchanged and move to its original position.

Ok.

quoted

  #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'.

quoted

  	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.

quoted

  
  	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.

quoted

  
  	ptl = pmd_lock(mm, pmdp);
  	pmd_clear_tests(mm, pmdp);

Thanks,
Gavin