Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1411 insertions, 0 deletions

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
new file mode 100644
index 0000000000..48e329ea5b
--- /dev/null
+++ b/mm/debug_vm_pgtable.c
@@ -0,0 +1,1411 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This kernel test validates architecture page table helpers and
+ * accessors and helps in verifying their continued compliance with
+ * expected generic MM semantics.
+ *
+ * Copyright (C) 2019 ARM Ltd.
+ *
+ * Author: Anshuman Khandual <anshuman.khandual@arm.com>
+ */
+#define pr_fmt(fmt) "debug_vm_pgtable: [%-25s]: " fmt, __func__
+
+#include <linux/gfp.h>
+#include <linux/highmem.h>
+#include <linux/hugetlb.h>
+#include <linux/kernel.h>
+#include <linux/kconfig.h>
+#include <linux/memblock.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/mm_types.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include <linux/printk.h>
+#include <linux/pgtable.h>
+#include <linux/random.h>
+#include <linux/spinlock.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/start_kernel.h>
+#include <linux/sched/mm.h>
+#include <linux/io.h>
+
+#include <asm/cacheflush.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+
+/*
+ * Please refer Documentation/mm/arch_pgtable_helpers.rst for the semantics
+ * expectations that are being validated here. All future changes in here
+ * or the documentation need to be in sync.
+ *
+ * On s390 platform, the lower 4 bits are used to identify given page table
+ * entry type. But these bits might affect the ability to clear entries with
+ * pxx_clear() because of how dynamic page table folding works on s390. So
+ * while loading up the entries do not change the lower 4 bits. It does not
+ * have affect any other platform. Also avoid the 62nd bit on ppc64 that is
+ * used to mark a pte entry.
+ */
+#define S390_SKIP_MASK		GENMASK(3, 0)
+#if __BITS_PER_LONG == 64
+#define PPC64_SKIP_MASK		GENMASK(62, 62)
+#else
+#define PPC64_SKIP_MASK		0x0
+#endif
+#define ARCH_SKIP_MASK (S390_SKIP_MASK | PPC64_SKIP_MASK)
+#define RANDOM_ORVALUE (GENMASK(BITS_PER_LONG - 1, 0) & ~ARCH_SKIP_MASK)
+#define RANDOM_NZVALUE	GENMASK(7, 0)
+
+struct pgtable_debug_args {
+	struct mm_struct	*mm;
+	struct vm_area_struct	*vma;
+
+	pgd_t			*pgdp;
+	p4d_t			*p4dp;
+	pud_t			*pudp;
+	pmd_t			*pmdp;
+	pte_t			*ptep;
+
+	p4d_t			*start_p4dp;
+	pud_t			*start_pudp;
+	pmd_t			*start_pmdp;
+	pgtable_t		start_ptep;
+
+	unsigned long		vaddr;
+	pgprot_t		page_prot;
+	pgprot_t		page_prot_none;
+
+	bool			is_contiguous_page;
+	unsigned long		pud_pfn;
+	unsigned long		pmd_pfn;
+	unsigned long		pte_pfn;
+
+	unsigned long		fixed_alignment;
+	unsigned long		fixed_pgd_pfn;
+	unsigned long		fixed_p4d_pfn;
+	unsigned long		fixed_pud_pfn;
+	unsigned long		fixed_pmd_pfn;
+	unsigned long		fixed_pte_pfn;
+};
+
+static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx)
+{
+	pgprot_t prot = vm_get_page_prot(idx);
+	pte_t pte = pfn_pte(args->fixed_pte_pfn, prot);
+	unsigned long val = idx, *ptr = &val;
+
+	pr_debug("Validating PTE basic (%pGv)\n", ptr);
+
+	/*
+	 * This test needs to be executed after the given page table entry
+	 * is created with pfn_pte() to make sure that vm_get_page_prot(idx)
+	 * does not have the dirty bit enabled from the beginning. This is
+	 * important for platforms like arm64 where (!PTE_RDONLY) indicate
+	 * dirty bit being set.
+	 */
+	WARN_ON(pte_dirty(pte_wrprotect(pte)));
+
+	WARN_ON(!pte_same(pte, pte));
+	WARN_ON(!pte_young(pte_mkyoung(pte_mkold(pte))));
+	WARN_ON(!pte_dirty(pte_mkdirty(pte_mkclean(pte))));
+	WARN_ON(!pte_write(pte_mkwrite(pte_wrprotect(pte), args->vma)));
+	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, args->vma))));
+	WARN_ON(pte_dirty(pte_wrprotect(pte_mkclean(pte))));
+	WARN_ON(!pte_dirty(pte_wrprotect(pte_mkdirty(pte))));
+}
+
+static void __init pte_advanced_tests(struct pgtable_debug_args *args)
+{
+	struct page *page;
+	pte_t pte;
+
+	/*
+	 * 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
+	 *
+	 * flush_dcache_page() is called after set_pte_at() to clear
+	 * PG_arch_1 for the page on ARM64. The page flag isn't cleared
+	 * when it's released and page allocation check will fail when
+	 * the page is allocated again. For architectures other than ARM64,
+	 * the unexpected overhead of cache flushing is acceptable.
+	 */
+	page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL;
+	if (!page)
+		return;
+
+	pr_debug("Validating PTE advanced\n");
+	if (WARN_ON(!args->ptep))
+		return;
+
+	pte = pfn_pte(args->pte_pfn, args->page_prot);
+	set_pte_at(args->mm, args->vaddr, args->ptep, pte);
+	flush_dcache_page(page);
+	ptep_set_wrprotect(args->mm, args->vaddr, args->ptep);
+	pte = ptep_get(args->ptep);
+	WARN_ON(pte_write(pte));
+	ptep_get_and_clear(args->mm, args->vaddr, args->ptep);
+	pte = ptep_get(args->ptep);
+	WARN_ON(!pte_none(pte));
+
+	pte = pfn_pte(args->pte_pfn, args->page_prot);
+	pte = pte_wrprotect(pte);
+	pte = pte_mkclean(pte);
+	set_pte_at(args->mm, args->vaddr, args->ptep, pte);
+	flush_dcache_page(page);
+	pte = pte_mkwrite(pte, args->vma);
+	pte = pte_mkdirty(pte);
+	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(args->mm, args->vaddr, args->ptep, 1);
+	pte = ptep_get(args->ptep);
+	WARN_ON(!pte_none(pte));
+
+	pte = pfn_pte(args->pte_pfn, args->page_prot);
+	pte = pte_mkyoung(pte);
+	set_pte_at(args->mm, args->vaddr, args->ptep, pte);
+	flush_dcache_page(page);
+	ptep_test_and_clear_young(args->vma, args->vaddr, args->ptep);
+	pte = ptep_get(args->ptep);
+	WARN_ON(pte_young(pte));
+
+	ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1);
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
+{
+	pgprot_t prot = vm_get_page_prot(idx);
+	unsigned long val = idx, *ptr = &val;
+	pmd_t pmd;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD basic (%pGv)\n", ptr);
+	pmd = pfn_pmd(args->fixed_pmd_pfn, prot);
+
+	/*
+	 * This test needs to be executed after the given page table entry
+	 * is created with pfn_pmd() to make sure that vm_get_page_prot(idx)
+	 * does not have the dirty bit enabled from the beginning. This is
+	 * important for platforms like arm64 where (!PTE_RDONLY) indicate
+	 * dirty bit being set.
+	 */
+	WARN_ON(pmd_dirty(pmd_wrprotect(pmd)));
+
+
+	WARN_ON(!pmd_same(pmd, pmd));
+	WARN_ON(!pmd_young(pmd_mkyoung(pmd_mkold(pmd))));
+	WARN_ON(!pmd_dirty(pmd_mkdirty(pmd_mkclean(pmd))));
+	WARN_ON(!pmd_write(pmd_mkwrite(pmd_wrprotect(pmd), args->vma)));
+	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, args->vma))));
+	WARN_ON(pmd_dirty(pmd_wrprotect(pmd_mkclean(pmd))));
+	WARN_ON(!pmd_dirty(pmd_wrprotect(pmd_mkdirty(pmd))));
+	/*
+	 * A huge page does not point to next level page table
+	 * entry. Hence this must qualify as pmd_bad().
+	 */
+	WARN_ON(!pmd_bad(pmd_mkhuge(pmd)));
+}
+
+static void __init pmd_advanced_tests(struct pgtable_debug_args *args)
+{
+	struct page *page;
+	pmd_t pmd;
+	unsigned long vaddr = args->vaddr;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	page = (args->pmd_pfn != ULONG_MAX) ? pfn_to_page(args->pmd_pfn) : NULL;
+	if (!page)
+		return;
+
+	/*
+	 * flush_dcache_page() is called after set_pmd_at() to clear
+	 * PG_arch_1 for the page on ARM64. The page flag isn't cleared
+	 * when it's released and page allocation check will fail when
+	 * the page is allocated again. For architectures other than ARM64,
+	 * the unexpected overhead of cache flushing is acceptable.
+	 */
+	pr_debug("Validating PMD advanced\n");
+	/* Align the address wrt HPAGE_PMD_SIZE */
+	vaddr &= HPAGE_PMD_MASK;
+
+	pgtable_trans_huge_deposit(args->mm, args->pmdp, args->start_ptep);
+
+	pmd = pfn_pmd(args->pmd_pfn, args->page_prot);
+	set_pmd_at(args->mm, vaddr, args->pmdp, pmd);
+	flush_dcache_page(page);
+	pmdp_set_wrprotect(args->mm, vaddr, args->pmdp);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(pmd_write(pmd));
+	pmdp_huge_get_and_clear(args->mm, vaddr, args->pmdp);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(!pmd_none(pmd));
+
+	pmd = pfn_pmd(args->pmd_pfn, args->page_prot);
+	pmd = pmd_wrprotect(pmd);
+	pmd = pmd_mkclean(pmd);
+	set_pmd_at(args->mm, vaddr, args->pmdp, pmd);
+	flush_dcache_page(page);
+	pmd = pmd_mkwrite(pmd, args->vma);
+	pmd = pmd_mkdirty(pmd);
+	pmdp_set_access_flags(args->vma, vaddr, args->pmdp, pmd, 1);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(!(pmd_write(pmd) && pmd_dirty(pmd)));
+	pmdp_huge_get_and_clear_full(args->vma, vaddr, args->pmdp, 1);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(!pmd_none(pmd));
+
+	pmd = pmd_mkhuge(pfn_pmd(args->pmd_pfn, args->page_prot));
+	pmd = pmd_mkyoung(pmd);
+	set_pmd_at(args->mm, vaddr, args->pmdp, pmd);
+	flush_dcache_page(page);
+	pmdp_test_and_clear_young(args->vma, vaddr, args->pmdp);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(pmd_young(pmd));
+
+	/*  Clear the pte entries  */
+	pmdp_huge_get_and_clear(args->mm, vaddr, args->pmdp);
+	pgtable_trans_huge_withdraw(args->mm, args->pmdp);
+}
+
+static void __init pmd_leaf_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD leaf\n");
+	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+
+	/*
+	 * PMD based THP is a leaf entry.
+	 */
+	pmd = pmd_mkhuge(pmd);
+	WARN_ON(!pmd_leaf(pmd));
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx)
+{
+	pgprot_t prot = vm_get_page_prot(idx);
+	unsigned long val = idx, *ptr = &val;
+	pud_t pud;
+
+	if (!has_transparent_pud_hugepage())
+		return;
+
+	pr_debug("Validating PUD basic (%pGv)\n", ptr);
+	pud = pfn_pud(args->fixed_pud_pfn, prot);
+
+	/*
+	 * This test needs to be executed after the given page table entry
+	 * is created with pfn_pud() to make sure that vm_get_page_prot(idx)
+	 * does not have the dirty bit enabled from the beginning. This is
+	 * important for platforms like arm64 where (!PTE_RDONLY) indicate
+	 * dirty bit being set.
+	 */
+	WARN_ON(pud_dirty(pud_wrprotect(pud)));
+
+	WARN_ON(!pud_same(pud, pud));
+	WARN_ON(!pud_young(pud_mkyoung(pud_mkold(pud))));
+	WARN_ON(!pud_dirty(pud_mkdirty(pud_mkclean(pud))));
+	WARN_ON(pud_dirty(pud_mkclean(pud_mkdirty(pud))));
+	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_mkclean(pud))));
+	WARN_ON(!pud_dirty(pud_wrprotect(pud_mkdirty(pud))));
+
+	if (mm_pmd_folded(args->mm))
+		return;
+
+	/*
+	 * A huge page does not point to next level page table
+	 * entry. Hence this must qualify as pud_bad().
+	 */
+	WARN_ON(!pud_bad(pud_mkhuge(pud)));
+}
+
+static void __init pud_advanced_tests(struct pgtable_debug_args *args)
+{
+	struct page *page;
+	unsigned long vaddr = args->vaddr;
+	pud_t pud;
+
+	if (!has_transparent_pud_hugepage())
+		return;
+
+	page = (args->pud_pfn != ULONG_MAX) ? pfn_to_page(args->pud_pfn) : NULL;
+	if (!page)
+		return;
+
+	/*
+	 * flush_dcache_page() is called after set_pud_at() to clear
+	 * PG_arch_1 for the page on ARM64. The page flag isn't cleared
+	 * when it's released and page allocation check will fail when
+	 * the page is allocated again. For architectures other than ARM64,
+	 * the unexpected overhead of cache flushing is acceptable.
+	 */
+	pr_debug("Validating PUD advanced\n");
+	/* Align the address wrt HPAGE_PUD_SIZE */
+	vaddr &= HPAGE_PUD_MASK;
+
+	pud = pfn_pud(args->pud_pfn, args->page_prot);
+	set_pud_at(args->mm, vaddr, args->pudp, pud);
+	flush_dcache_page(page);
+	pudp_set_wrprotect(args->mm, vaddr, args->pudp);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(pud_write(pud));
+
+#ifndef __PAGETABLE_PMD_FOLDED
+	pudp_huge_get_and_clear(args->mm, vaddr, args->pudp);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(!pud_none(pud));
+#endif /* __PAGETABLE_PMD_FOLDED */
+	pud = pfn_pud(args->pud_pfn, args->page_prot);
+	pud = pud_wrprotect(pud);
+	pud = pud_mkclean(pud);
+	set_pud_at(args->mm, vaddr, args->pudp, pud);
+	flush_dcache_page(page);
+	pud = pud_mkwrite(pud);
+	pud = pud_mkdirty(pud);
+	pudp_set_access_flags(args->vma, vaddr, args->pudp, pud, 1);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(!(pud_write(pud) && pud_dirty(pud)));
+
+#ifndef __PAGETABLE_PMD_FOLDED
+	pudp_huge_get_and_clear_full(args->vma, vaddr, args->pudp, 1);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(!pud_none(pud));
+#endif /* __PAGETABLE_PMD_FOLDED */
+
+	pud = pfn_pud(args->pud_pfn, args->page_prot);
+	pud = pud_mkyoung(pud);
+	set_pud_at(args->mm, vaddr, args->pudp, pud);
+	flush_dcache_page(page);
+	pudp_test_and_clear_young(args->vma, vaddr, args->pudp);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(pud_young(pud));
+
+	pudp_huge_get_and_clear(args->mm, vaddr, args->pudp);
+}
+
+static void __init pud_leaf_tests(struct pgtable_debug_args *args)
+{
+	pud_t pud;
+
+	if (!has_transparent_pud_hugepage())
+		return;
+
+	pr_debug("Validating PUD leaf\n");
+	pud = pfn_pud(args->fixed_pud_pfn, args->page_prot);
+	/*
+	 * PUD based THP is a leaf entry.
+	 */
+	pud = pud_mkhuge(pud);
+	WARN_ON(!pud_leaf(pud));
+}
+#else  /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { }
+static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
+static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+#else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
+static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx) { }
+static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx) { }
+static void __init pmd_advanced_tests(struct pgtable_debug_args *args) { }
+static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
+static void __init pmd_leaf_tests(struct pgtable_debug_args *args) { }
+static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
+static void __init pmd_huge_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!arch_vmap_pmd_supported(args->page_prot) ||
+	    args->fixed_alignment < PMD_SIZE)
+		return;
+
+	pr_debug("Validating PMD huge\n");
+	/*
+	 * X86 defined pmd_set_huge() verifies that the given
+	 * PMD is not a populated non-leaf entry.
+	 */
+	WRITE_ONCE(*args->pmdp, __pmd(0));
+	WARN_ON(!pmd_set_huge(args->pmdp, __pfn_to_phys(args->fixed_pmd_pfn), args->page_prot));
+	WARN_ON(!pmd_clear_huge(args->pmdp));
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(!pmd_none(pmd));
+}
+
+static void __init pud_huge_tests(struct pgtable_debug_args *args)
+{
+	pud_t pud;
+
+	if (!arch_vmap_pud_supported(args->page_prot) ||
+	    args->fixed_alignment < PUD_SIZE)
+		return;
+
+	pr_debug("Validating PUD huge\n");
+	/*
+	 * X86 defined pud_set_huge() verifies that the given
+	 * PUD is not a populated non-leaf entry.
+	 */
+	WRITE_ONCE(*args->pudp, __pud(0));
+	WARN_ON(!pud_set_huge(args->pudp, __pfn_to_phys(args->fixed_pud_pfn), args->page_prot));
+	WARN_ON(!pud_clear_huge(args->pudp));
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(!pud_none(pud));
+}
+#else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
+static void __init pmd_huge_tests(struct pgtable_debug_args *args) { }
+static void __init pud_huge_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */
+
+static void __init p4d_basic_tests(struct pgtable_debug_args *args)
+{
+	p4d_t p4d;
+
+	pr_debug("Validating P4D basic\n");
+	memset(&p4d, RANDOM_NZVALUE, sizeof(p4d_t));
+	WARN_ON(!p4d_same(p4d, p4d));
+}
+
+static void __init pgd_basic_tests(struct pgtable_debug_args *args)
+{
+	pgd_t pgd;
+
+	pr_debug("Validating PGD basic\n");
+	memset(&pgd, RANDOM_NZVALUE, sizeof(pgd_t));
+	WARN_ON(!pgd_same(pgd, pgd));
+}
+
+#ifndef __PAGETABLE_PUD_FOLDED
+static void __init pud_clear_tests(struct pgtable_debug_args *args)
+{
+	pud_t pud = READ_ONCE(*args->pudp);
+
+	if (mm_pmd_folded(args->mm))
+		return;
+
+	pr_debug("Validating PUD clear\n");
+	pud = __pud(pud_val(pud) | RANDOM_ORVALUE);
+	WRITE_ONCE(*args->pudp, pud);
+	pud_clear(args->pudp);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(!pud_none(pud));
+}
+
+static void __init pud_populate_tests(struct pgtable_debug_args *args)
+{
+	pud_t pud;
+
+	if (mm_pmd_folded(args->mm))
+		return;
+
+	pr_debug("Validating PUD populate\n");
+	/*
+	 * This entry points to next level page table page.
+	 * Hence this must not qualify as pud_bad().
+	 */
+	pud_populate(args->mm, args->pudp, args->start_pmdp);
+	pud = READ_ONCE(*args->pudp);
+	WARN_ON(pud_bad(pud));
+}
+#else  /* !__PAGETABLE_PUD_FOLDED */
+static void __init pud_clear_tests(struct pgtable_debug_args *args) { }
+static void __init pud_populate_tests(struct pgtable_debug_args *args) { }
+#endif /* PAGETABLE_PUD_FOLDED */
+
+#ifndef __PAGETABLE_P4D_FOLDED
+static void __init p4d_clear_tests(struct pgtable_debug_args *args)
+{
+	p4d_t p4d = READ_ONCE(*args->p4dp);
+
+	if (mm_pud_folded(args->mm))
+		return;
+
+	pr_debug("Validating P4D clear\n");
+	p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE);
+	WRITE_ONCE(*args->p4dp, p4d);
+	p4d_clear(args->p4dp);
+	p4d = READ_ONCE(*args->p4dp);
+	WARN_ON(!p4d_none(p4d));
+}
+
+static void __init p4d_populate_tests(struct pgtable_debug_args *args)
+{
+	p4d_t p4d;
+
+	if (mm_pud_folded(args->mm))
+		return;
+
+	pr_debug("Validating P4D populate\n");
+	/*
+	 * This entry points to next level page table page.
+	 * Hence this must not qualify as p4d_bad().
+	 */
+	pud_clear(args->pudp);
+	p4d_clear(args->p4dp);
+	p4d_populate(args->mm, args->p4dp, args->start_pudp);
+	p4d = READ_ONCE(*args->p4dp);
+	WARN_ON(p4d_bad(p4d));
+}
+
+static void __init pgd_clear_tests(struct pgtable_debug_args *args)
+{
+	pgd_t pgd = READ_ONCE(*(args->pgdp));
+
+	if (mm_p4d_folded(args->mm))
+		return;
+
+	pr_debug("Validating PGD clear\n");
+	pgd = __pgd(pgd_val(pgd) | RANDOM_ORVALUE);
+	WRITE_ONCE(*args->pgdp, pgd);
+	pgd_clear(args->pgdp);
+	pgd = READ_ONCE(*args->pgdp);
+	WARN_ON(!pgd_none(pgd));
+}
+
+static void __init pgd_populate_tests(struct pgtable_debug_args *args)
+{
+	pgd_t pgd;
+
+	if (mm_p4d_folded(args->mm))
+		return;
+
+	pr_debug("Validating PGD populate\n");
+	/*
+	 * This entry points to next level page table page.
+	 * Hence this must not qualify as pgd_bad().
+	 */
+	p4d_clear(args->p4dp);
+	pgd_clear(args->pgdp);
+	pgd_populate(args->mm, args->pgdp, args->start_p4dp);
+	pgd = READ_ONCE(*args->pgdp);
+	WARN_ON(pgd_bad(pgd));
+}
+#else  /* !__PAGETABLE_P4D_FOLDED */
+static void __init p4d_clear_tests(struct pgtable_debug_args *args) { }
+static void __init pgd_clear_tests(struct pgtable_debug_args *args) { }
+static void __init p4d_populate_tests(struct pgtable_debug_args *args) { }
+static void __init pgd_populate_tests(struct pgtable_debug_args *args) { }
+#endif /* PAGETABLE_P4D_FOLDED */
+
+static void __init pte_clear_tests(struct pgtable_debug_args *args)
+{
+	struct page *page;
+	pte_t pte = pfn_pte(args->pte_pfn, args->page_prot);
+
+	page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL;
+	if (!page)
+		return;
+
+	/*
+	 * flush_dcache_page() is called after set_pte_at() to clear
+	 * PG_arch_1 for the page on ARM64. The page flag isn't cleared
+	 * when it's released and page allocation check will fail when
+	 * the page is allocated again. For architectures other than ARM64,
+	 * the unexpected overhead of cache flushing is acceptable.
+	 */
+	pr_debug("Validating PTE clear\n");
+	if (WARN_ON(!args->ptep))
+		return;
+
+#ifndef CONFIG_RISCV
+	pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
+#endif
+	set_pte_at(args->mm, args->vaddr, args->ptep, pte);
+	flush_dcache_page(page);
+	barrier();
+	ptep_clear(args->mm, args->vaddr, args->ptep);
+	pte = ptep_get(args->ptep);
+	WARN_ON(!pte_none(pte));
+}
+
+static void __init pmd_clear_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd = READ_ONCE(*args->pmdp);
+
+	pr_debug("Validating PMD clear\n");
+	pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE);
+	WRITE_ONCE(*args->pmdp, pmd);
+	pmd_clear(args->pmdp);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(!pmd_none(pmd));
+}
+
+static void __init pmd_populate_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	pr_debug("Validating PMD populate\n");
+	/*
+	 * This entry points to next level page table page.
+	 * Hence this must not qualify as pmd_bad().
+	 */
+	pmd_populate(args->mm, args->pmdp, args->start_ptep);
+	pmd = READ_ONCE(*args->pmdp);
+	WARN_ON(pmd_bad(pmd));
+}
+
+static void __init pte_special_tests(struct pgtable_debug_args *args)
+{
+	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
+
+	if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL))
+		return;
+
+	pr_debug("Validating PTE special\n");
+	WARN_ON(!pte_special(pte_mkspecial(pte)));
+}
+
+static void __init pte_protnone_tests(struct pgtable_debug_args *args)
+{
+	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot_none);
+
+	if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
+		return;
+
+	pr_debug("Validating PTE protnone\n");
+	WARN_ON(!pte_protnone(pte));
+	WARN_ON(!pte_present(pte));
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void __init pmd_protnone_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
+		return;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD protnone\n");
+	pmd = pmd_mkhuge(pfn_pmd(args->fixed_pmd_pfn, args->page_prot_none));
+	WARN_ON(!pmd_protnone(pmd));
+	WARN_ON(!pmd_present(pmd));
+}
+#else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
+static void __init pmd_protnone_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+#ifdef CONFIG_ARCH_HAS_PTE_DEVMAP
+static void __init pte_devmap_tests(struct pgtable_debug_args *args)
+{
+	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
+
+	pr_debug("Validating PTE devmap\n");
+	WARN_ON(!pte_devmap(pte_mkdevmap(pte)));
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void __init pmd_devmap_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD devmap\n");
+	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+	WARN_ON(!pmd_devmap(pmd_mkdevmap(pmd)));
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static void __init pud_devmap_tests(struct pgtable_debug_args *args)
+{
+	pud_t pud;
+
+	if (!has_transparent_pud_hugepage())
+		return;
+
+	pr_debug("Validating PUD devmap\n");
+	pud = pfn_pud(args->fixed_pud_pfn, args->page_prot);
+	WARN_ON(!pud_devmap(pud_mkdevmap(pud)));
+}
+#else  /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+static void __init pud_devmap_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+#else  /* CONFIG_TRANSPARENT_HUGEPAGE */
+static void __init pmd_devmap_tests(struct pgtable_debug_args *args) { }
+static void __init pud_devmap_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#else
+static void __init pte_devmap_tests(struct pgtable_debug_args *args) { }
+static void __init pmd_devmap_tests(struct pgtable_debug_args *args) { }
+static void __init pud_devmap_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_ARCH_HAS_PTE_DEVMAP */
+
+static void __init pte_soft_dirty_tests(struct pgtable_debug_args *args)
+{
+	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
+
+	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+		return;
+
+	pr_debug("Validating PTE soft dirty\n");
+	WARN_ON(!pte_soft_dirty(pte_mksoft_dirty(pte)));
+	WARN_ON(pte_soft_dirty(pte_clear_soft_dirty(pte)));
+}
+
+static void __init pte_swap_soft_dirty_tests(struct pgtable_debug_args *args)
+{
+	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
+
+	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+		return;
+
+	pr_debug("Validating PTE swap soft dirty\n");
+	WARN_ON(!pte_swp_soft_dirty(pte_swp_mksoft_dirty(pte)));
+	WARN_ON(pte_swp_soft_dirty(pte_swp_clear_soft_dirty(pte)));
+}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+		return;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD soft dirty\n");
+	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+	WARN_ON(!pmd_soft_dirty(pmd_mksoft_dirty(pmd)));
+	WARN_ON(pmd_soft_dirty(pmd_clear_soft_dirty(pmd)));
+}
+
+static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) ||
+		!IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION))
+		return;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD swap soft dirty\n");
+	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+	WARN_ON(!pmd_swp_soft_dirty(pmd_swp_mksoft_dirty(pmd)));
+	WARN_ON(pmd_swp_soft_dirty(pmd_swp_clear_soft_dirty(pmd)));
+}
+#else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
+static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args) { }
+static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args)
+{
+	unsigned long max_swap_offset;
+	swp_entry_t entry, entry2;
+	pte_t pte;
+
+	pr_debug("Validating PTE swap exclusive\n");
+
+	/* See generic_max_swapfile_size(): probe the maximum offset */
+	max_swap_offset = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0, ~0UL))));
+
+	/* Create a swp entry with all possible bits set */
+	entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, max_swap_offset);
+
+	pte = swp_entry_to_pte(entry);
+	WARN_ON(pte_swp_exclusive(pte));
+	WARN_ON(!is_swap_pte(pte));
+	entry2 = pte_to_swp_entry(pte);
+	WARN_ON(memcmp(&entry, &entry2, sizeof(entry)));
+
+	pte = pte_swp_mkexclusive(pte);
+	WARN_ON(!pte_swp_exclusive(pte));
+	WARN_ON(!is_swap_pte(pte));
+	WARN_ON(pte_swp_soft_dirty(pte));
+	entry2 = pte_to_swp_entry(pte);
+	WARN_ON(memcmp(&entry, &entry2, sizeof(entry)));
+
+	pte = pte_swp_clear_exclusive(pte);
+	WARN_ON(pte_swp_exclusive(pte));
+	WARN_ON(!is_swap_pte(pte));
+	entry2 = pte_to_swp_entry(pte);
+	WARN_ON(memcmp(&entry, &entry2, sizeof(entry)));
+}
+
+static void __init pte_swap_tests(struct pgtable_debug_args *args)
+{
+	swp_entry_t swp;
+	pte_t pte;
+
+	pr_debug("Validating PTE swap\n");
+	pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
+	swp = __pte_to_swp_entry(pte);
+	pte = __swp_entry_to_pte(swp);
+	WARN_ON(args->fixed_pte_pfn != pte_pfn(pte));
+}
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static void __init pmd_swap_tests(struct pgtable_debug_args *args)
+{
+	swp_entry_t swp;
+	pmd_t pmd;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD swap\n");
+	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+	swp = __pmd_to_swp_entry(pmd);
+	pmd = __swp_entry_to_pmd(swp);
+	WARN_ON(args->fixed_pmd_pfn != pmd_pfn(pmd));
+}
+#else  /* !CONFIG_ARCH_ENABLE_THP_MIGRATION */
+static void __init pmd_swap_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
+
+static void __init swap_migration_tests(struct pgtable_debug_args *args)
+{
+	struct page *page;
+	swp_entry_t swp;
+
+	if (!IS_ENABLED(CONFIG_MIGRATION))
+		return;
+
+	/*
+	 * swap_migration_tests() requires a dedicated page as it needs to
+	 * be locked before creating a migration entry from it. Locking the
+	 * page that actually maps kernel text ('start_kernel') can be real
+	 * problematic. Lets use the allocated page explicitly for this
+	 * purpose.
+	 */
+	page = (args->pte_pfn != ULONG_MAX) ? pfn_to_page(args->pte_pfn) : NULL;
+	if (!page)
+		return;
+
+	pr_debug("Validating swap migration\n");
+
+	/*
+	 * make_[readable|writable]_migration_entry() expects given page to
+	 * be locked, otherwise it stumbles upon a BUG_ON().
+	 */
+	__SetPageLocked(page);
+	swp = make_writable_migration_entry(page_to_pfn(page));
+	WARN_ON(!is_migration_entry(swp));
+	WARN_ON(!is_writable_migration_entry(swp));
+
+	swp = make_readable_migration_entry(swp_offset(swp));
+	WARN_ON(!is_migration_entry(swp));
+	WARN_ON(is_writable_migration_entry(swp));
+
+	swp = make_readable_migration_entry(page_to_pfn(page));
+	WARN_ON(!is_migration_entry(swp));
+	WARN_ON(is_writable_migration_entry(swp));
+	__ClearPageLocked(page);
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static void __init hugetlb_basic_tests(struct pgtable_debug_args *args)
+{
+	struct page *page;
+	pte_t pte;
+
+	pr_debug("Validating HugeTLB basic\n");
+	/*
+	 * Accessing the page associated with the pfn is safe here,
+	 * as it was previously derived from a real kernel symbol.
+	 */
+	page = pfn_to_page(args->fixed_pmd_pfn);
+	pte = mk_huge_pte(page, args->page_prot);
+
+	WARN_ON(!huge_pte_dirty(huge_pte_mkdirty(pte)));
+	WARN_ON(!huge_pte_write(huge_pte_mkwrite(huge_pte_wrprotect(pte))));
+	WARN_ON(huge_pte_write(huge_pte_wrprotect(huge_pte_mkwrite(pte))));
+
+#ifdef CONFIG_ARCH_WANT_GENERAL_HUGETLB
+	pte = pfn_pte(args->fixed_pmd_pfn, args->page_prot);
+
+	WARN_ON(!pte_huge(arch_make_huge_pte(pte, PMD_SHIFT, VM_ACCESS_FLAGS)));
+#endif /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
+}
+#else  /* !CONFIG_HUGETLB_PAGE */
+static void __init hugetlb_basic_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_HUGETLB_PAGE */
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void __init pmd_thp_tests(struct pgtable_debug_args *args)
+{
+	pmd_t pmd;
+
+	if (!has_transparent_hugepage())
+		return;
+
+	pr_debug("Validating PMD based THP\n");
+	/*
+	 * pmd_trans_huge() and pmd_present() must return positive after
+	 * MMU invalidation with pmd_mkinvalid(). This behavior is an
+	 * optimization for transparent huge page. pmd_trans_huge() must
+	 * be true if pmd_page() returns a valid THP to avoid taking the
+	 * pmd_lock when others walk over non transhuge pmds (i.e. there
+	 * are no THP allocated). Especially when splitting a THP and
+	 * removing the present bit from the pmd, pmd_trans_huge() still
+	 * needs to return true. pmd_present() should be true whenever
+	 * pmd_trans_huge() returns true.
+	 */
+	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot);
+	WARN_ON(!pmd_trans_huge(pmd_mkhuge(pmd)));
+
+#ifndef __HAVE_ARCH_PMDP_INVALIDATE
+	WARN_ON(!pmd_trans_huge(pmd_mkinvalid(pmd_mkhuge(pmd))));
+	WARN_ON(!pmd_present(pmd_mkinvalid(pmd_mkhuge(pmd))));
+#endif /* __HAVE_ARCH_PMDP_INVALIDATE */
+}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static void __init pud_thp_tests(struct pgtable_debug_args *args)
+{
+	pud_t pud;
+
+	if (!has_transparent_pud_hugepage())
+		return;
+
+	pr_debug("Validating PUD based THP\n");
+	pud = pfn_pud(args->fixed_pud_pfn, args->page_prot);
+	WARN_ON(!pud_trans_huge(pud_mkhuge(pud)));
+
+	/*
+	 * pud_mkinvalid() has been dropped for now. Enable back
+	 * these tests when it comes back with a modified pud_present().
+	 *
+	 * WARN_ON(!pud_trans_huge(pud_mkinvalid(pud_mkhuge(pud))));
+	 * WARN_ON(!pud_present(pud_mkinvalid(pud_mkhuge(pud))));
+	 */
+}
+#else  /* !CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+static void __init pud_thp_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */
+#else  /* !CONFIG_TRANSPARENT_HUGEPAGE */
+static void __init pmd_thp_tests(struct pgtable_debug_args *args) { }
+static void __init pud_thp_tests(struct pgtable_debug_args *args) { }
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+
+static unsigned long __init get_random_vaddr(void)
+{
+	unsigned long random_vaddr, random_pages, total_user_pages;
+
+	total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE;
+
+	random_pages = get_random_long() % total_user_pages;
+	random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE;
+
+	return random_vaddr;
+}
+
+static void __init destroy_args(struct pgtable_debug_args *args)
+{
+	struct page *page = NULL;
+
+	/* Free (huge) page */
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	    has_transparent_pud_hugepage() &&
+	    args->pud_pfn != ULONG_MAX) {
+		if (args->is_contiguous_page) {
+			free_contig_range(args->pud_pfn,
+					  (1 << (HPAGE_PUD_SHIFT - PAGE_SHIFT)));
+		} else {
+			page = pfn_to_page(args->pud_pfn);
+			__free_pages(page, HPAGE_PUD_SHIFT - PAGE_SHIFT);
+		}
+
+		args->pud_pfn = ULONG_MAX;
+		args->pmd_pfn = ULONG_MAX;
+		args->pte_pfn = ULONG_MAX;
+	}
+
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	    has_transparent_hugepage() &&
+	    args->pmd_pfn != ULONG_MAX) {
+		if (args->is_contiguous_page) {
+			free_contig_range(args->pmd_pfn, (1 << HPAGE_PMD_ORDER));
+		} else {
+			page = pfn_to_page(args->pmd_pfn);
+			__free_pages(page, HPAGE_PMD_ORDER);
+		}
+
+		args->pmd_pfn = ULONG_MAX;
+		args->pte_pfn = ULONG_MAX;
+	}
+
+	if (args->pte_pfn != ULONG_MAX) {
+		page = pfn_to_page(args->pte_pfn);
+		__free_page(page);
+
+		args->pte_pfn = ULONG_MAX;
+	}
+
+	/* Free page table entries */
+	if (args->start_ptep) {
+		pte_free(args->mm, args->start_ptep);
+		mm_dec_nr_ptes(args->mm);
+	}
+
+	if (args->start_pmdp) {
+		pmd_free(args->mm, args->start_pmdp);
+		mm_dec_nr_pmds(args->mm);
+	}
+
+	if (args->start_pudp) {
+		pud_free(args->mm, args->start_pudp);
+		mm_dec_nr_puds(args->mm);
+	}
+
+	if (args->start_p4dp)
+		p4d_free(args->mm, args->start_p4dp);
+
+	/* Free vma and mm struct */
+	if (args->vma)
+		vm_area_free(args->vma);
+
+	if (args->mm)
+		mmdrop(args->mm);
+}
+
+static struct page * __init
+debug_vm_pgtable_alloc_huge_page(struct pgtable_debug_args *args, int order)
+{
+	struct page *page = NULL;
+
+#ifdef CONFIG_CONTIG_ALLOC
+	if (order > MAX_ORDER) {
+		page = alloc_contig_pages((1 << order), GFP_KERNEL,
+					  first_online_node, NULL);
+		if (page) {
+			args->is_contiguous_page = true;
+			return page;
+		}
+	}
+#endif
+
+	if (order <= MAX_ORDER)
+		page = alloc_pages(GFP_KERNEL, order);
+
+	return page;
+}
+
+/*
+ * Check if a physical memory range described by <pstart, pend> contains
+ * an area that is of size psize, and aligned to psize.
+ *
+ * Don't use address 0, an all-zeroes physical address might mask bugs, and
+ * it's not used on x86.
+ */
+static void  __init phys_align_check(phys_addr_t pstart,
+				     phys_addr_t pend, unsigned long psize,
+				     phys_addr_t *physp, unsigned long *alignp)
+{
+	phys_addr_t aligned_start, aligned_end;
+
+	if (pstart == 0)
+		pstart = PAGE_SIZE;
+
+	aligned_start = ALIGN(pstart, psize);
+	aligned_end = aligned_start + psize;
+
+	if (aligned_end > aligned_start && aligned_end <= pend) {
+		*alignp = psize;
+		*physp = aligned_start;
+	}
+}
+
+static void __init init_fixed_pfns(struct pgtable_debug_args *args)
+{
+	u64 idx;
+	phys_addr_t phys, pstart, pend;
+
+	/*
+	 * Initialize the fixed pfns. To do this, try to find a
+	 * valid physical range, preferably aligned to PUD_SIZE,
+	 * but settling for aligned to PMD_SIZE as a fallback. If
+	 * neither of those is found, use the physical address of
+	 * the start_kernel symbol.
+	 *
+	 * The memory doesn't need to be allocated, it just needs to exist
+	 * as usable memory. It won't be touched.
+	 *
+	 * The alignment is recorded, and can be checked to see if we
+	 * can run the tests that require an actual valid physical
+	 * address range on some architectures ({pmd,pud}_huge_test
+	 * on x86).
+	 */
+
+	phys = __pa_symbol(&start_kernel);
+	args->fixed_alignment = PAGE_SIZE;
+
+	for_each_mem_range(idx, &pstart, &pend) {
+		/* First check for a PUD-aligned area */
+		phys_align_check(pstart, pend, PUD_SIZE, &phys,
+				 &args->fixed_alignment);
+
+		/* If a PUD-aligned area is found, we're done */
+		if (args->fixed_alignment == PUD_SIZE)
+			break;
+
+		/*
+		 * If no PMD-aligned area found yet, check for one,
+		 * but continue the loop to look for a PUD-aligned area.
+		 */
+		if (args->fixed_alignment < PMD_SIZE)
+			phys_align_check(pstart, pend, PMD_SIZE, &phys,
+					 &args->fixed_alignment);
+	}
+
+	args->fixed_pgd_pfn = __phys_to_pfn(phys & PGDIR_MASK);
+	args->fixed_p4d_pfn = __phys_to_pfn(phys & P4D_MASK);
+	args->fixed_pud_pfn = __phys_to_pfn(phys & PUD_MASK);
+	args->fixed_pmd_pfn = __phys_to_pfn(phys & PMD_MASK);
+	args->fixed_pte_pfn = __phys_to_pfn(phys & PAGE_MASK);
+	WARN_ON(!pfn_valid(args->fixed_pte_pfn));
+}
+
+
+static int __init init_args(struct pgtable_debug_args *args)
+{
+	struct page *page = NULL;
+	int ret = 0;
+
+	/*
+	 * Initialize the debugging data.
+	 *
+	 * vm_get_page_prot(VM_NONE) or vm_get_page_prot(VM_SHARED|VM_NONE)
+	 * will help create page table entries with PROT_NONE permission as
+	 * required for pxx_protnone_tests().
+	 */
+	memset(args, 0, sizeof(*args));
+	args->vaddr              = get_random_vaddr();
+	args->page_prot          = vm_get_page_prot(VM_ACCESS_FLAGS);
+	args->page_prot_none     = vm_get_page_prot(VM_NONE);
+	args->is_contiguous_page = false;
+	args->pud_pfn            = ULONG_MAX;
+	args->pmd_pfn            = ULONG_MAX;
+	args->pte_pfn            = ULONG_MAX;
+	args->fixed_pgd_pfn      = ULONG_MAX;
+	args->fixed_p4d_pfn      = ULONG_MAX;
+	args->fixed_pud_pfn      = ULONG_MAX;
+	args->fixed_pmd_pfn      = ULONG_MAX;
+	args->fixed_pte_pfn      = ULONG_MAX;
+
+	/* Allocate mm and vma */
+	args->mm = mm_alloc();
+	if (!args->mm) {
+		pr_err("Failed to allocate mm struct\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	args->vma = vm_area_alloc(args->mm);
+	if (!args->vma) {
+		pr_err("Failed to allocate vma\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	/*
+	 * Allocate page table entries. They will be modified in the tests.
+	 * Lets save the page table entries so that they can be released
+	 * when the tests are completed.
+	 */
+	args->pgdp = pgd_offset(args->mm, args->vaddr);
+	args->p4dp = p4d_alloc(args->mm, args->pgdp, args->vaddr);
+	if (!args->p4dp) {
+		pr_err("Failed to allocate p4d entries\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+	args->start_p4dp = p4d_offset(args->pgdp, 0UL);
+	WARN_ON(!args->start_p4dp);
+
+	args->pudp = pud_alloc(args->mm, args->p4dp, args->vaddr);
+	if (!args->pudp) {
+		pr_err("Failed to allocate pud entries\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+	args->start_pudp = pud_offset(args->p4dp, 0UL);
+	WARN_ON(!args->start_pudp);
+
+	args->pmdp = pmd_alloc(args->mm, args->pudp, args->vaddr);
+	if (!args->pmdp) {
+		pr_err("Failed to allocate pmd entries\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+	args->start_pmdp = pmd_offset(args->pudp, 0UL);
+	WARN_ON(!args->start_pmdp);
+
+	if (pte_alloc(args->mm, args->pmdp)) {
+		pr_err("Failed to allocate pte entries\n");
+		ret = -ENOMEM;
+		goto error;
+	}
+	args->start_ptep = pmd_pgtable(READ_ONCE(*args->pmdp));
+	WARN_ON(!args->start_ptep);
+
+	init_fixed_pfns(args);
+
+	/*
+	 * Allocate (huge) pages because some of the tests need to access
+	 * the data in the pages. The corresponding tests will be skipped
+	 * if we fail to allocate (huge) pages.
+	 */
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	    has_transparent_pud_hugepage()) {
+		page = debug_vm_pgtable_alloc_huge_page(args,
+				HPAGE_PUD_SHIFT - PAGE_SHIFT);
+		if (page) {
+			args->pud_pfn = page_to_pfn(page);
+			args->pmd_pfn = args->pud_pfn;
+			args->pte_pfn = args->pud_pfn;
+			return 0;
+		}
+	}
+
+	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) &&
+	    has_transparent_hugepage()) {
+		page = debug_vm_pgtable_alloc_huge_page(args, HPAGE_PMD_ORDER);
+		if (page) {
+			args->pmd_pfn = page_to_pfn(page);
+			args->pte_pfn = args->pmd_pfn;
+			return 0;
+		}
+	}
+
+	page = alloc_page(GFP_KERNEL);
+	if (page)
+		args->pte_pfn = page_to_pfn(page);
+
+	return 0;
+
+error:
+	destroy_args(args);
+	return ret;
+}
+
+static int __init debug_vm_pgtable(void)
+{
+	struct pgtable_debug_args args;
+	spinlock_t *ptl = NULL;
+	int idx, ret;
+
+	pr_info("Validating architecture page table helpers\n");
+	ret = init_args(&args);
+	if (ret)
+		return ret;
+
+	/*
+	 * Iterate over each possible vm_flags to make sure that all
+	 * the basic page table transformation validations just hold
+	 * true irrespective of the starting protection value for a
+	 * given page table entry.
+	 *
+	 * Protection based vm_flags combinatins are always linear
+	 * and increasing i.e starting from VM_NONE and going upto
+	 * (VM_SHARED | READ | WRITE | EXEC).
+	 */
+#define VM_FLAGS_START	(VM_NONE)
+#define VM_FLAGS_END	(VM_SHARED | VM_EXEC | VM_WRITE | VM_READ)
+
+	for (idx = VM_FLAGS_START; idx <= VM_FLAGS_END; idx++) {
+		pte_basic_tests(&args, idx);
+		pmd_basic_tests(&args, idx);
+		pud_basic_tests(&args, idx);
+	}
+
+	/*
+	 * Both P4D and PGD level tests are very basic which do not
+	 * involve creating page table entries from the protection
+	 * value and the given pfn. Hence just keep them out from
+	 * the above iteration for now to save some test execution
+	 * time.
+	 */
+	p4d_basic_tests(&args);
+	pgd_basic_tests(&args);
+
+	pmd_leaf_tests(&args);
+	pud_leaf_tests(&args);
+
+	pte_special_tests(&args);
+	pte_protnone_tests(&args);
+	pmd_protnone_tests(&args);
+
+	pte_devmap_tests(&args);
+	pmd_devmap_tests(&args);
+	pud_devmap_tests(&args);
+
+	pte_soft_dirty_tests(&args);
+	pmd_soft_dirty_tests(&args);
+	pte_swap_soft_dirty_tests(&args);
+	pmd_swap_soft_dirty_tests(&args);
+
+	pte_swap_exclusive_tests(&args);
+
+	pte_swap_tests(&args);
+	pmd_swap_tests(&args);
+
+	swap_migration_tests(&args);
+
+	pmd_thp_tests(&args);
+	pud_thp_tests(&args);
+
+	hugetlb_basic_tests(&args);
+
+	/*
+	 * Page table modifying tests. They need to hold
+	 * proper page table lock.
+	 */
+
+	args.ptep = pte_offset_map_lock(args.mm, args.pmdp, args.vaddr, &ptl);
+	pte_clear_tests(&args);
+	pte_advanced_tests(&args);
+	if (args.ptep)
+		pte_unmap_unlock(args.ptep, ptl);
+
+	ptl = pmd_lock(args.mm, args.pmdp);
+	pmd_clear_tests(&args);
+	pmd_advanced_tests(&args);
+	pmd_huge_tests(&args);
+	pmd_populate_tests(&args);
+	spin_unlock(ptl);
+
+	ptl = pud_lock(args.mm, args.pudp);
+	pud_clear_tests(&args);
+	pud_advanced_tests(&args);
+	pud_huge_tests(&args);
+	pud_populate_tests(&args);
+	spin_unlock(ptl);
+
+	spin_lock(&(args.mm->page_table_lock));
+	p4d_clear_tests(&args);
+	pgd_clear_tests(&args);
+	p4d_populate_tests(&args);
+	pgd_populate_tests(&args);
+	spin_unlock(&(args.mm->page_table_lock));
+
+	destroy_args(&args);
+	return 0;
+}
+late_initcall(debug_vm_pgtable);