mm/debug_vm_pgtable/set_pte/pmd/pud: don't use set_*_at to update an existing pte...

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.

Link: https://lkml.kernel.org/r/20200902114222.181353-8-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 8704901f6bd8af01deac57e109422163df4e6606..2ba5ec866f5368c17655c728f53dd229247e78ee 100644 (file)
--- 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 = 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);
@@ -291,17 +287,9 @@ static void __init pud_advanced_tests(struct mm_struct *mm,
        WARN_ON(pud_write(pud));
 
 #ifndef __PAGETABLE_PMD_FOLDED
-       pud = 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 = 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 = pfn_pud(pfn, prot);
        pud = pud_wrprotect(pud);
@@ -313,6 +301,13 @@ 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 = pfn_pud(pfn, prot);
        pud = pud_mkyoung(pud);
        set_pud_at(mm, vaddr, pudp, pud);
        pudp_test_and_clear_young(vma, vaddr, pudp);