arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables

In many cases, page tables can be accessed concurrently by either another
CPU (due to things like fast gup) or by the hardware page table walker
itself, which may set access/dirty bits. In such cases, it is important
to use READ_ONCE/WRITE_ONCE when accessing page table entries so that
entries cannot be torn, merged or subject to apparent loss of coherence
due to compiler transformations.

Whilst there are some scenarios where this cannot happen (e.g. pinned
kernel mappings for the linear region), the overhead of using READ_ONCE
/WRITE_ONCE everywhere is minimal and makes the code an awful lot easier
to reason about. This patch consistently uses these macros in the arch
code, as well as explicitly namespacing pointers to page table entries
from the entries themselves by using adopting a 'p' suffix for the former
(as is sometimes used elsewhere in the kernel source).
Tested-by: Yury Norov <ynorov@caviumnetworks.com>
Tested-by: Richard Ruigrok <rruigrok@codeaurora.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/hugetlb.h

@@ -22,7 +22,7 @@
 
 static inline pte_t huge_ptep_get(pte_t *ptep)
 {
-	return *ptep;
+	return READ_ONCE(*ptep);
 }
 
 

arch/arm64/include/asm/kvm_mmu.h

@@ -185,42 +185,42 @@ static inline pmd_t kvm_s2pmd_mkexec(pmd_t pmd)
 	return pmd;
 }
 
-static inline void kvm_set_s2pte_readonly(pte_t *pte)
+static inline void kvm_set_s2pte_readonly(pte_t *ptep)
 {
 	pteval_t old_pteval, pteval;
 
-	pteval = READ_ONCE(pte_val(*pte));
+	pteval = READ_ONCE(pte_val(*ptep));
 	do {
 		old_pteval = pteval;
 		pteval &= ~PTE_S2_RDWR;
 		pteval |= PTE_S2_RDONLY;
-		pteval = cmpxchg_relaxed(&pte_val(*pte), old_pteval, pteval);
+		pteval = cmpxchg_relaxed(&pte_val(*ptep), old_pteval, pteval);
 	} while (pteval != old_pteval);
 }
 
-static inline bool kvm_s2pte_readonly(pte_t *pte)
+static inline bool kvm_s2pte_readonly(pte_t *ptep)
 {
-	return (pte_val(*pte) & PTE_S2_RDWR) == PTE_S2_RDONLY;
+	return (READ_ONCE(pte_val(*ptep)) & PTE_S2_RDWR) == PTE_S2_RDONLY;
 }
 
-static inline bool kvm_s2pte_exec(pte_t *pte)
+static inline bool kvm_s2pte_exec(pte_t *ptep)
 {
-	return !(pte_val(*pte) & PTE_S2_XN);
+	return !(READ_ONCE(pte_val(*ptep)) & PTE_S2_XN);
 }
 
-static inline void kvm_set_s2pmd_readonly(pmd_t *pmd)
+static inline void kvm_set_s2pmd_readonly(pmd_t *pmdp)
 {
-	kvm_set_s2pte_readonly((pte_t *)pmd);
+	kvm_set_s2pte_readonly((pte_t *)pmdp);
 }
 
-static inline bool kvm_s2pmd_readonly(pmd_t *pmd)
+static inline bool kvm_s2pmd_readonly(pmd_t *pmdp)
 {
-	return kvm_s2pte_readonly((pte_t *)pmd);
+	return kvm_s2pte_readonly((pte_t *)pmdp);
 }
 
-static inline bool kvm_s2pmd_exec(pmd_t *pmd)
+static inline bool kvm_s2pmd_exec(pmd_t *pmdp)
 {
-	return !(pmd_val(*pmd) & PMD_S2_XN);
+	return !(READ_ONCE(pmd_val(*pmdp)) & PMD_S2_XN);
 }
 
 static inline bool kvm_page_empty(void *ptr)

arch/arm64/include/asm/mmu_context.h

@@ -141,13 +141,13 @@ static inline void cpu_install_idmap(void)
  * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
  * avoiding the possibility of conflicting TLB entries being allocated.
  */
-static inline void cpu_replace_ttbr1(pgd_t *pgd)
+static inline void cpu_replace_ttbr1(pgd_t *pgdp)
 {
 	typedef void (ttbr_replace_func)(phys_addr_t);
 	extern ttbr_replace_func idmap_cpu_replace_ttbr1;
 	ttbr_replace_func *replace_phys;
 
-	phys_addr_t pgd_phys = virt_to_phys(pgd);
+	phys_addr_t pgd_phys = virt_to_phys(pgdp);
 
 	replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);
 

arch/arm64/include/asm/pgalloc.h

@@ -36,23 +36,23 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
 	return (pmd_t *)__get_free_page(PGALLOC_GFP);
 }
 
-static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
+static inline void pmd_free(struct mm_struct *mm, pmd_t *pmdp)
 {
-	BUG_ON((unsigned long)pmd & (PAGE_SIZE-1));
-	free_page((unsigned long)pmd);
+	BUG_ON((unsigned long)pmdp & (PAGE_SIZE-1));
+	free_page((unsigned long)pmdp);
 }
 
-static inline void __pud_populate(pud_t *pud, phys_addr_t pmd, pudval_t prot)
+static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot)
 {
-	set_pud(pud, __pud(__phys_to_pud_val(pmd) | prot));
+	set_pud(pudp, __pud(__phys_to_pud_val(pmdp) | prot));
 }
 
-static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
+static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
 {
-	__pud_populate(pud, __pa(pmd), PMD_TYPE_TABLE);
+	__pud_populate(pudp, __pa(pmdp), PMD_TYPE_TABLE);
 }
 #else
-static inline void __pud_populate(pud_t *pud, phys_addr_t pmd, pudval_t prot)
+static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot)
 {
 	BUILD_BUG();
 }
@@ -65,30 +65,30 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
 	return (pud_t *)__get_free_page(PGALLOC_GFP);
 }
 
-static inline void pud_free(struct mm_struct *mm, pud_t *pud)
+static inline void pud_free(struct mm_struct *mm, pud_t *pudp)
 {
-	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
-	free_page((unsigned long)pud);
+	BUG_ON((unsigned long)pudp & (PAGE_SIZE-1));
+	free_page((unsigned long)pudp);
 }
 
-static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pud, pgdval_t prot)
+static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pudp, pgdval_t prot)
 {
-	set_pgd(pgdp, __pgd(__phys_to_pgd_val(pud) | prot));
+	set_pgd(pgdp, __pgd(__phys_to_pgd_val(pudp) | prot));
 }
 
-static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
+static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgdp, pud_t *pudp)
 {
-	__pgd_populate(pgd, __pa(pud), PUD_TYPE_TABLE);
+	__pgd_populate(pgdp, __pa(pudp), PUD_TYPE_TABLE);
 }
 #else
-static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pud, pgdval_t prot)
+static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pudp, pgdval_t prot)
 {
 	BUILD_BUG();
 }
 #endif	/* CONFIG_PGTABLE_LEVELS > 3 */
 
 extern pgd_t *pgd_alloc(struct mm_struct *mm);
-extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
+extern void pgd_free(struct mm_struct *mm, pgd_t *pgdp);
 
 static inline pte_t *
 pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr)
@@ -114,10 +114,10 @@ pte_alloc_one(struct mm_struct *mm, unsigned long addr)
 /*
  * Free a PTE table.
  */
-static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
+static inline void pte_free_kernel(struct mm_struct *mm, pte_t *ptep)
 {
-	if (pte)
-		free_page((unsigned long)pte);
+	if (ptep)
+		free_page((unsigned long)ptep);
 }
 
 static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
@@ -126,10 +126,10 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
 	__free_page(pte);
 }
 
-static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t pte,
+static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t ptep,
 				  pmdval_t prot)
 {
-	set_pmd(pmdp, __pmd(__phys_to_pmd_val(pte) | prot));
+	set_pmd(pmdp, __pmd(__phys_to_pmd_val(ptep) | prot));
 }
 
 /*

arch/arm64/include/asm/pgtable.h

@@ -218,7 +218,7 @@ static inline pmd_t pmd_mkcont(pmd_t pmd)
 
 static inline void set_pte(pte_t *ptep, pte_t pte)
 {
-	*ptep = pte;
+	WRITE_ONCE(*ptep, pte);
 
 	/*
 	 * Only if the new pte is valid and kernel, otherwise TLB maintenance
@@ -250,6 +250,8 @@ extern void __sync_icache_dcache(pte_t pteval, unsigned long addr);
 static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 			      pte_t *ptep, pte_t pte)
 {
+	pte_t old_pte;
+
 	if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
 		__sync_icache_dcache(pte, addr);
 
@@ -258,14 +260,15 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 	 * hardware updates of the pte (ptep_set_access_flags safely changes
 	 * valid ptes without going through an invalid entry).
 	 */
-	if (IS_ENABLED(CONFIG_DEBUG_VM) && pte_valid(*ptep) && pte_valid(pte) &&
+	old_pte = READ_ONCE(*ptep);
+	if (IS_ENABLED(CONFIG_DEBUG_VM) && pte_valid(old_pte) && pte_valid(pte) &&
 	   (mm == current->active_mm || atomic_read(&mm->mm_users) > 1)) {
 		VM_WARN_ONCE(!pte_young(pte),
 			     "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
-			     __func__, pte_val(*ptep), pte_val(pte));
-		VM_WARN_ONCE(pte_write(*ptep) && !pte_dirty(pte),
+			     __func__, pte_val(old_pte), pte_val(pte));
+		VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte),
 			     "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
-			     __func__, pte_val(*ptep), pte_val(pte));
+			     __func__, pte_val(old_pte), pte_val(pte));
 	}
 
 	set_pte(ptep, pte);
@@ -431,7 +434,7 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 
 static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
 {
-	*pmdp = pmd;
+	WRITE_ONCE(*pmdp, pmd);
 	dsb(ishst);
 	isb();
 }
@@ -482,7 +485,7 @@ static inline phys_addr_t pmd_page_paddr(pmd_t pmd)
 
 static inline void set_pud(pud_t *pudp, pud_t pud)
 {
-	*pudp = pud;
+	WRITE_ONCE(*pudp, pud);
 	dsb(ishst);
 	isb();
 }
@@ -500,7 +503,7 @@ static inline phys_addr_t pud_page_paddr(pud_t pud)
 /* Find an entry in the second-level page table. */
 #define pmd_index(addr)		(((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
 
-#define pmd_offset_phys(dir, addr)	(pud_page_paddr(*(dir)) + pmd_index(addr) * sizeof(pmd_t))
+#define pmd_offset_phys(dir, addr)	(pud_page_paddr(READ_ONCE(*(dir))) + pmd_index(addr) * sizeof(pmd_t))
 #define pmd_offset(dir, addr)		((pmd_t *)__va(pmd_offset_phys((dir), (addr))))
 
 #define pmd_set_fixmap(addr)		((pmd_t *)set_fixmap_offset(FIX_PMD, addr))
@@ -535,7 +538,7 @@ static inline phys_addr_t pud_page_paddr(pud_t pud)
 
 static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)
 {
-	*pgdp = pgd;
+	WRITE_ONCE(*pgdp, pgd);
 	dsb(ishst);
 }
 
@@ -552,7 +555,7 @@ static inline phys_addr_t pgd_page_paddr(pgd_t pgd)
 /* Find an entry in the frst-level page table. */
 #define pud_index(addr)		(((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
 
-#define pud_offset_phys(dir, addr)	(pgd_page_paddr(*(dir)) + pud_index(addr) * sizeof(pud_t))
+#define pud_offset_phys(dir, addr)	(pgd_page_paddr(READ_ONCE(*(dir))) + pud_index(addr) * sizeof(pud_t))
 #define pud_offset(dir, addr)		((pud_t *)__va(pud_offset_phys((dir), (addr))))
 
 #define pud_set_fixmap(addr)		((pud_t *)set_fixmap_offset(FIX_PUD, addr))

arch/arm64/kernel/efi.c

@@ -90,7 +90,7 @@ static int __init set_permissions(pte_t *ptep, pgtable_t token,
 				  unsigned long addr, void *data)
 {
 	efi_memory_desc_t *md = data;
-	pte_t pte = *ptep;
+	pte_t pte = READ_ONCE(*ptep);
 
 	if (md->attribute & EFI_MEMORY_RO)
 		pte = set_pte_bit(pte, __pgprot(PTE_RDONLY));

arch/arm64/kernel/hibernate.c

@@ -202,10 +202,10 @@ static int create_safe_exec_page(void *src_start, size_t length,
 				 gfp_t mask)
 {
 	int rc = 0;
-	pgd_t *pgd;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
+	pgd_t *pgdp;
+	pud_t *pudp;
+	pmd_t *pmdp;
+	pte_t *ptep;
 	unsigned long dst = (unsigned long)allocator(mask);
 
 	if (!dst) {
@@ -216,38 +216,38 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	memcpy((void *)dst, src_start, length);
 	flush_icache_range(dst, dst + length);
 
-	pgd = pgd_offset_raw(allocator(mask), dst_addr);
-	if (pgd_none(*pgd)) {
-		pud = allocator(mask);
-		if (!pud) {
+	pgdp = pgd_offset_raw(allocator(mask), dst_addr);
+	if (pgd_none(READ_ONCE(*pgdp))) {
+		pudp = allocator(mask);
+		if (!pudp) {
 			rc = -ENOMEM;
 			goto out;
 		}
-		pgd_populate(&init_mm, pgd, pud);
+		pgd_populate(&init_mm, pgdp, pudp);
 	}
 
-	pud = pud_offset(pgd, dst_addr);
-	if (pud_none(*pud)) {
-		pmd = allocator(mask);
-		if (!pmd) {
+	pudp = pud_offset(pgdp, dst_addr);
+	if (pud_none(READ_ONCE(*pudp))) {
+		pmdp = allocator(mask);
+		if (!pmdp) {
 			rc = -ENOMEM;
 			goto out;
 		}
-		pud_populate(&init_mm, pud, pmd);
+		pud_populate(&init_mm, pudp, pmdp);
 	}
 
-	pmd = pmd_offset(pud, dst_addr);
-	if (pmd_none(*pmd)) {
-		pte = allocator(mask);
-		if (!pte) {
+	pmdp = pmd_offset(pudp, dst_addr);
+	if (pmd_none(READ_ONCE(*pmdp))) {
+		ptep = allocator(mask);
+		if (!ptep) {
 			rc = -ENOMEM;
 			goto out;
 		}
-		pmd_populate_kernel(&init_mm, pmd, pte);
+		pmd_populate_kernel(&init_mm, pmdp, ptep);
 	}
 
-	pte = pte_offset_kernel(pmd, dst_addr);
-	set_pte(pte, pfn_pte(virt_to_pfn(dst), PAGE_KERNEL_EXEC));
+	ptep = pte_offset_kernel(pmdp, dst_addr);
+	set_pte(ptep, pfn_pte(virt_to_pfn(dst), PAGE_KERNEL_EXEC));
 
 	/*
 	 * Load our new page tables. A strict BBM approach requires that we
@@ -263,7 +263,7 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	 */
 	cpu_set_reserved_ttbr0();
 	local_flush_tlb_all();
-	write_sysreg(phys_to_ttbr(virt_to_phys(pgd)), ttbr0_el1);
+	write_sysreg(phys_to_ttbr(virt_to_phys(pgdp)), ttbr0_el1);
 	isb();
 
 	*phys_dst_addr = virt_to_phys((void *)dst);
@@ -320,9 +320,9 @@ int swsusp_arch_suspend(void)
 	return ret;
 }
 
-static void _copy_pte(pte_t *dst_pte, pte_t *src_pte, unsigned long addr)
+static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr)
 {
-	pte_t pte = *src_pte;
+	pte_t pte = READ_ONCE(*src_ptep);
 
 	if (pte_valid(pte)) {
 		/*
@@ -330,7 +330,7 @@ static void _copy_pte(pte_t *dst_pte, pte_t *src_pte, unsigned long addr)
 		 * read only (code, rodata). Clear the RDONLY bit from
 		 * the temporary mappings we use during restore.
 		 */
-		set_pte(dst_pte, pte_mkwrite(pte));
+		set_pte(dst_ptep, pte_mkwrite(pte));
 	} else if (debug_pagealloc_enabled() && !pte_none(pte)) {
 		/*
 		 * debug_pagealloc will removed the PTE_VALID bit if
@@ -343,112 +343,116 @@ static void _copy_pte(pte_t *dst_pte, pte_t *src_pte, unsigned long addr)
 		 */
 		BUG_ON(!pfn_valid(pte_pfn(pte)));
 
-		set_pte(dst_pte, pte_mkpresent(pte_mkwrite(pte)));
+		set_pte(dst_ptep, pte_mkpresent(pte_mkwrite(pte)));
 	}
 }
 
-static int copy_pte(pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long start,
+static int copy_pte(pmd_t *dst_pmdp, pmd_t *src_pmdp, unsigned long start,
 		    unsigned long end)
 {
-	pte_t *src_pte;
-	pte_t *dst_pte;
+	pte_t *src_ptep;
+	pte_t *dst_ptep;
 	unsigned long addr = start;
 
-	dst_pte = (pte_t *)get_safe_page(GFP_ATOMIC);
-	if (!dst_pte)
+	dst_ptep = (pte_t *)get_safe_page(GFP_ATOMIC);
+	if (!dst_ptep)
 		return -ENOMEM;
-	pmd_populate_kernel(&init_mm, dst_pmd, dst_pte);
-	dst_pte = pte_offset_kernel(dst_pmd, start);
+	pmd_populate_kernel(&init_mm, dst_pmdp, dst_ptep);
+	dst_ptep = pte_offset_kernel(dst_pmdp, start);
 
-	src_pte = pte_offset_kernel(src_pmd, start);
+	src_ptep = pte_offset_kernel(src_pmdp, start);
 	do {
-		_copy_pte(dst_pte, src_pte, addr);
-	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);
+		_copy_pte(dst_ptep, src_ptep, addr);
+	} while (dst_ptep++, src_ptep++, addr += PAGE_SIZE, addr != end);
 
 	return 0;
 }
 
-static int copy_pmd(pud_t *dst_pud, pud_t *src_pud, unsigned long start,
+static int copy_pmd(pud_t *dst_pudp, pud_t *src_pudp, unsigned long start,
 		    unsigned long end)
 {
-	pmd_t *src_pmd;
-	pmd_t *dst_pmd;
+	pmd_t *src_pmdp;
+	pmd_t *dst_pmdp;
 	unsigned long next;
 	unsigned long addr = start;
 
-	if (pud_none(*dst_pud)) {
-		dst_pmd = (pmd_t *)get_safe_page(GFP_ATOMIC);
-		if (!dst_pmd)
+	if (pud_none(READ_ONCE(*dst_pudp))) {
+		dst_pmdp = (pmd_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_pmdp)
 			return -ENOMEM;
-		pud_populate(&init_mm, dst_pud, dst_pmd);
+		pud_populate(&init_mm, dst_pudp, dst_pmdp);
 	}
-	dst_pmd = pmd_offset(dst_pud, start);
+	dst_pmdp = pmd_offset(dst_pudp, start);
 
-	src_pmd = pmd_offset(src_pud, start);
+	src_pmdp = pmd_offset(src_pudp, start);
 	do {
+		pmd_t pmd = READ_ONCE(*src_pmdp);
+
 		next = pmd_addr_end(addr, end);
-		if (pmd_none(*src_pmd))
+		if (pmd_none(pmd))
 			continue;
-		if (pmd_table(*src_pmd)) {
-			if (copy_pte(dst_pmd, src_pmd, addr, next))
+		if (pmd_table(pmd)) {
+			if (copy_pte(dst_pmdp, src_pmdp, addr, next))
 				return -ENOMEM;
 		} else {
-			set_pmd(dst_pmd,
-				__pmd(pmd_val(*src_pmd) & ~PMD_SECT_RDONLY));
+			set_pmd(dst_pmdp,
+				__pmd(pmd_val(pmd) & ~PMD_SECT_RDONLY));
 		}
-	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
+	} while (dst_pmdp++, src_pmdp++, addr = next, addr != end);
 
 	return 0;
 }
 
-static int copy_pud(pgd_t *dst_pgd, pgd_t *src_pgd, unsigned long start,
+static int copy_pud(pgd_t *dst_pgdp, pgd_t *src_pgdp, unsigned long start,
 		    unsigned long end)
 {
-	pud_t *dst_pud;
-	pud_t *src_pud;
+	pud_t *dst_pudp;
+	pud_t *src_pudp;
 	unsigned long next;
 	unsigned long addr = start;
 
-	if (pgd_none(*dst_pgd)) {
-		dst_pud = (pud_t *)get_safe_page(GFP_ATOMIC);
-		if (!dst_pud)
+	if (pgd_none(READ_ONCE(*dst_pgdp))) {
+		dst_pudp = (pud_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_pudp)
 			return -ENOMEM;
-		pgd_populate(&init_mm, dst_pgd, dst_pud);
+		pgd_populate(&init_mm, dst_pgdp, dst_pudp);
 	}
-	dst_pud = pud_offset(dst_pgd, start);
+	dst_pudp = pud_offset(dst_pgdp, start);
 
-	src_pud = pud_offset(src_pgd, start);
+	src_pudp = pud_offset(src_pgdp, start);
 	do {
+		pud_t pud = READ_ONCE(*src_pudp);
+
 		next = pud_addr_end(addr, end);
-		if (pud_none(*src_pud))
+		if (pud_none(pud))
 			continue;
-		if (pud_table(*(src_pud))) {
-			if (copy_pmd(dst_pud, src_pud, addr, next))
+		if (pud_table(pud)) {
+			if (copy_pmd(dst_pudp, src_pudp, addr, next))
 				return -ENOMEM;
 		} else {
-			set_pud(dst_pud,
-				__pud(pud_val(*src_pud) & ~PMD_SECT_RDONLY));
+			set_pud(dst_pudp,
+				__pud(pud_val(pud) & ~PMD_SECT_RDONLY));
 		}
-	} while (dst_pud++, src_pud++, addr = next, addr != end);
+	} while (dst_pudp++, src_pudp++, addr = next, addr != end);
 
 	return 0;
 }
 
-static int copy_page_tables(pgd_t *dst_pgd, unsigned long start,
+static int copy_page_tables(pgd_t *dst_pgdp, unsigned long start,
 			    unsigned long end)
 {
 	unsigned long next;
 	unsigned long addr = start;
-	pgd_t *src_pgd = pgd_offset_k(start);
+	pgd_t *src_pgdp = pgd_offset_k(start);
 
-	dst_pgd = pgd_offset_raw(dst_pgd, start);
+	dst_pgdp = pgd_offset_raw(dst_pgdp, start);
 	do {
 		next = pgd_addr_end(addr, end);
-		if (pgd_none(*src_pgd))
+		if (pgd_none(READ_ONCE(*src_pgdp)))
 			continue;
-		if (copy_pud(dst_pgd, src_pgd, addr, next))
+		if (copy_pud(dst_pgdp, src_pgdp, addr, next))
 			return -ENOMEM;
-	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
+	} while (dst_pgdp++, src_pgdp++, addr = next, addr != end);
 
 	return 0;
 }

arch/arm64/mm/dump.c

@@ -286,48 +286,52 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
 
 }
 
-static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
+static void walk_pte(struct pg_state *st, pmd_t *pmdp, unsigned long start)
 {
-	pte_t *pte = pte_offset_kernel(pmd, 0UL);
+	pte_t *ptep = pte_offset_kernel(pmdp, 0UL);
 	unsigned long addr;
 	unsigned i;
 
-	for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
+	for (i = 0; i < PTRS_PER_PTE; i++, ptep++) {
 		addr = start + i * PAGE_SIZE;
-		note_page(st, addr, 4, pte_val(*pte));
+		note_page(st, addr, 4, READ_ONCE(pte_val(*ptep)));
 	}
 }
 
-static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
+static void walk_pmd(struct pg_state *st, pud_t *pudp, unsigned long start)
 {
-	pmd_t *pmd = pmd_offset(pud, 0UL);
+	pmd_t *pmdp = pmd_offset(pudp, 0UL);
 	unsigned long addr;
 	unsigned i;
 
-	for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
+	for (i = 0; i < PTRS_PER_PMD; i++, pmdp++) {
+		pmd_t pmd = READ_ONCE(*pmdp);
+
 		addr = start + i * PMD_SIZE;
-		if (pmd_none(*pmd) || pmd_sect(*pmd)) {
-			note_page(st, addr, 3, pmd_val(*pmd));
+		if (pmd_none(pmd) || pmd_sect(pmd)) {
+			note_page(st, addr, 3, pmd_val(pmd));
 		} else {
-			BUG_ON(pmd_bad(*pmd));
-			walk_pte(st, pmd, addr);
+			BUG_ON(pmd_bad(pmd));
+			walk_pte(st, pmdp, addr);
 		}
 	}
 }
 
-static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
+static void walk_pud(struct pg_state *st, pgd_t *pgdp, unsigned long start)
 {
-	pud_t *pud = pud_offset(pgd, 0UL);
+	pud_t *pudp = pud_offset(pgdp, 0UL);
 	unsigned long addr;
 	unsigned i;
 
-	for (i = 0; i < PTRS_PER_PUD; i++, pud++) {
+	for (i = 0; i < PTRS_PER_PUD; i++, pudp++) {
+		pud_t pud = READ_ONCE(*pudp);
+
 		addr = start + i * PUD_SIZE;
-		if (pud_none(*pud) || pud_sect(*pud)) {
-			note_page(st, addr, 2, pud_val(*pud));
+		if (pud_none(pud) || pud_sect(pud)) {
+			note_page(st, addr, 2, pud_val(pud));
 		} else {
-			BUG_ON(pud_bad(*pud));
-			walk_pmd(st, pud, addr);
+			BUG_ON(pud_bad(pud));
+			walk_pmd(st, pudp, addr);
 		}
 	}
 }
@@ -335,17 +339,19 @@ static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
 static void walk_pgd(struct pg_state *st, struct mm_struct *mm,
 		     unsigned long start)
 {
-	pgd_t *pgd = pgd_offset(mm, 0UL);
+	pgd_t *pgdp = pgd_offset(mm, 0UL);
 	unsigned i;
 	unsigned long addr;
 
-	for (i = 0; i < PTRS_PER_PGD; i++, pgd++) {
+	for (i = 0; i < PTRS_PER_PGD; i++, pgdp++) {
+		pgd_t pgd = READ_ONCE(*pgdp);
+
 		addr = start + i * PGDIR_SIZE;
-		if (pgd_none(*pgd)) {
-			note_page(st, addr, 1, pgd_val(*pgd));
+		if (pgd_none(pgd)) {
+			note_page(st, addr, 1, pgd_val(pgd));
 		} else {
-			BUG_ON(pgd_bad(*pgd));
-			walk_pud(st, pgd, addr);
+			BUG_ON(pgd_bad(pgd));
+			walk_pud(st, pgdp, addr);
 		}
 	}
 }

arch/arm64/mm/fault.c

@@ -130,7 +130,8 @@ static void mem_abort_decode(unsigned int esr)
 void show_pte(unsigned long addr)
 {
 	struct mm_struct *mm;
-	pgd_t *pgd;
+	pgd_t *pgdp;
+	pgd_t pgd;
 
 	if (addr < TASK_SIZE) {
 		/* TTBR0 */
@@ -149,33 +150,37 @@ void show_pte(unsigned long addr)
 		return;
 	}
 
-	pr_alert("%s pgtable: %luk pages, %u-bit VAs, pgd = %p\n",
+	pr_alert("%s pgtable: %luk pages, %u-bit VAs, pgdp = %p\n",
 		 mm == &init_mm ? "swapper" : "user", PAGE_SIZE / SZ_1K,
 		 VA_BITS, mm->pgd);
-	pgd = pgd_offset(mm, addr);
-	pr_alert("[%016lx] *pgd=%016llx", addr, pgd_val(*pgd));
+	pgdp = pgd_offset(mm, addr);
+	pgd = READ_ONCE(*pgdp);
+	pr_alert("[%016lx] pgd=%016llx", addr, pgd_val(pgd));
 
 	do {
-		pud_t *pud;
-		pmd_t *pmd;
-		pte_t *pte;
+		pud_t *pudp, pud;
+		pmd_t *pmdp, pmd;
+		pte_t *ptep, pte;
 
-		if (pgd_none(*pgd) || pgd_bad(*pgd))
+		if (pgd_none(pgd) || pgd_bad(pgd))
 			break;
 
-		pud = pud_offset(pgd, addr);
-		pr_cont(", *pud=%016llx", pud_val(*pud));
-		if (pud_none(*pud) || pud_bad(*pud))
+		pudp = pud_offset(pgdp, addr);
+		pud = READ_ONCE(*pudp);
+		pr_cont(", pud=%016llx", pud_val(pud));
+		if (pud_none(pud) || pud_bad(pud))
 			break;
 
-		pmd = pmd_offset(pud, addr);
-		pr_cont(", *pmd=%016llx", pmd_val(*pmd));
-		if (pmd_none(*pmd) || pmd_bad(*pmd))
+		pmdp = pmd_offset(pudp, addr);
+		pmd = READ_ONCE(*pmdp);
+		pr_cont(", pmd=%016llx", pmd_val(pmd));
+		if (pmd_none(pmd) || pmd_bad(pmd))
 			break;
 
-		pte = pte_offset_map(pmd, addr);
-		pr_cont(", *pte=%016llx", pte_val(*pte));
-		pte_unmap(pte);
+		ptep = pte_offset_map(pmdp, addr);
+		pte = READ_ONCE(*ptep);
+		pr_cont(", pte=%016llx", pte_val(pte));
+		pte_unmap(ptep);
 	} while(0);
 
 	pr_cont("\n");
@@ -196,8 +201,9 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
 			  pte_t entry, int dirty)
 {
 	pteval_t old_pteval, pteval;
+	pte_t pte = READ_ONCE(*ptep);
 
-	if (pte_same(*ptep, entry))
+	if (pte_same(pte, entry))
 		return 0;
 
 	/* only preserve the access flags and write permission */
@@ -210,7 +216,7 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
 	 * (calculated as: a & b == ~(~a | ~b)).
 	 */
 	pte_val(entry) ^= PTE_RDONLY;
-	pteval = READ_ONCE(pte_val(*ptep));
+	pteval = pte_val(pte);
 	do {
 		old_pteval = pteval;
 		pteval ^= PTE_RDONLY;

arch/arm64/mm/hugetlbpage.c

@@ -54,14 +54,14 @@ static inline pgprot_t pte_pgprot(pte_t pte)
 static int find_num_contig(struct mm_struct *mm, unsigned long addr,
 			   pte_t *ptep, size_t *pgsize)
 {
-	pgd_t *pgd = pgd_offset(mm, addr);
-	pud_t *pud;
-	pmd_t *pmd;
+	pgd_t *pgdp = pgd_offset(mm, addr);
+	pud_t *pudp;
+	pmd_t *pmdp;
 
 	*pgsize = PAGE_SIZE;
-	pud = pud_offset(pgd, addr);
-	pmd = pmd_offset(pud, addr);
-	if ((pte_t *)pmd == ptep) {
+	pudp = pud_offset(pgdp, addr);
+	pmdp = pmd_offset(pudp, addr);
+	if ((pte_t *)pmdp == ptep) {
 		*pgsize = PMD_SIZE;
 		return CONT_PMDS;
 	}
@@ -181,11 +181,8 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
 
 	clear_flush(mm, addr, ptep, pgsize, ncontig);
 
-	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn) {
-		pr_debug("%s: set pte %p to 0x%llx\n", __func__, ptep,
-			 pte_val(pfn_pte(pfn, hugeprot)));
+	for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
 		set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
-	}
 }
 
 void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
@@ -203,20 +200,20 @@ void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
 pte_t *huge_pte_alloc(struct mm_struct *mm,
 		      unsigned long addr, unsigned long sz)
 {
-	pgd_t *pgd;
-	pud_t *pud;
-	pte_t *pte = NULL;
-
-	pr_debug("%s: addr:0x%lx sz:0x%lx\n", __func__, addr, sz);
-	pgd = pgd_offset(mm, addr);
-	pud = pud_alloc(mm, pgd, addr);
-	if (!pud)
+	pgd_t *pgdp;
+	pud_t *pudp;
+	pmd_t *pmdp;
+	pte_t *ptep = NULL;
+
+	pgdp = pgd_offset(mm, addr);
+	pudp = pud_alloc(mm, pgdp, addr);
+	if (!pudp)
 		return NULL;
 
 	if (sz == PUD_SIZE) {
-		pte = (pte_t *)pud;
+		ptep = (pte_t *)pudp;
 	} else if (sz == (PAGE_SIZE * CONT_PTES)) {
-		pmd_t *pmd = pmd_alloc(mm, pud, addr);
+		pmdp = pmd_alloc(mm, pudp, addr);
 
 		WARN_ON(addr & (sz - 1));
 		/*
@@ -226,60 +223,55 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
 		 * will be no pte_unmap() to correspond with this
 		 * pte_alloc_map().
 		 */
-		pte = pte_alloc_map(mm, pmd, addr);
+		ptep = pte_alloc_map(mm, pmdp, addr);
 	} else if (sz == PMD_SIZE) {
 		if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
-		    pud_none(*pud))
-			pte = huge_pmd_share(mm, addr, pud);
+		    pud_none(READ_ONCE(*pudp)))
+			ptep = huge_pmd_share(mm, addr, pudp);
 		else
-			pte = (pte_t *)pmd_alloc(mm, pud, addr);
+			ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
 	} else if (sz == (PMD_SIZE * CONT_PMDS)) {
-		pmd_t *pmd;
-
-		pmd = pmd_alloc(mm, pud, addr);
+		pmdp = pmd_alloc(mm, pudp, addr);
 		WARN_ON(addr & (sz - 1));
-		return (pte_t *)pmd;
+		return (pte_t *)pmdp;
 	}
 
-	pr_debug("%s: addr:0x%lx sz:0x%lx ret pte=%p/0x%llx\n", __func__, addr,
-	       sz, pte, pte_val(*pte));
-	return pte;
+	return ptep;
 }
 
 pte_t *huge_pte_offset(struct mm_struct *mm,
 		       unsigned long addr, unsigned long sz)
 {
-	pgd_t *pgd;
-	pud_t *pud;
-	pmd_t *pmd;
+	pgd_t *pgdp;
+	pud_t *pudp, pud;
+	pmd_t *pmdp, pmd;
 
-	pgd = pgd_offset(mm, addr);
-	pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
-	if (!pgd_present(*pgd))
+	pgdp = pgd_offset(mm, addr);
+	if (!pgd_present(READ_ONCE(*pgdp)))
 		return NULL;
 
-	pud = pud_offset(pgd, addr);
-	if (sz != PUD_SIZE && pud_none(*pud))
+	pudp = pud_offset(pgdp, addr);
+	pud = READ_ONCE(*pudp);
+	if (sz != PUD_SIZE && pud_none(pud))
 		return NULL;
 	/* hugepage or swap? */
-	if (pud_huge(*pud) || !pud_present(*pud))
-		return (pte_t *)pud;
+	if (pud_huge(pud) || !pud_present(pud))
+		return (pte_t *)pudp;
 	/* table; check the next level */
 
 	if (sz == CONT_PMD_SIZE)
 		addr &= CONT_PMD_MASK;
 
-	pmd = pmd_offset(pud, addr);
+	pmdp = pmd_offset(pudp, addr);
+	pmd = READ_ONCE(*pmdp);
 	if (!(sz == PMD_SIZE || sz == CONT_PMD_SIZE) &&
-	    pmd_none(*pmd))
+	    pmd_none(pmd))
 		return NULL;
-	if (pmd_huge(*pmd) || !pmd_present(*pmd))
-		return (pte_t *)pmd;
+	if (pmd_huge(pmd) || !pmd_present(pmd))
+		return (pte_t *)pmdp;
 
-	if (sz == CONT_PTE_SIZE) {
-		pte_t *pte = pte_offset_kernel(pmd, (addr & CONT_PTE_MASK));
-		return pte;
-	}
+	if (sz == CONT_PTE_SIZE)
+		return pte_offset_kernel(pmdp, (addr & CONT_PTE_MASK));
 
 	return NULL;
 }
@@ -367,7 +359,7 @@ void huge_ptep_set_wrprotect(struct mm_struct *mm,
 	size_t pgsize;
 	pte_t pte;
 
-	if (!pte_cont(*ptep)) {
+	if (!pte_cont(READ_ONCE(*ptep))) {
 		ptep_set_wrprotect(mm, addr, ptep);
 		return;
 	}
@@ -391,7 +383,7 @@ void huge_ptep_clear_flush(struct vm_area_struct *vma,
 	size_t pgsize;
 	int ncontig;
 
-	if (!pte_cont(*ptep)) {
+	if (!pte_cont(READ_ONCE(*ptep))) {
 		ptep_clear_flush(vma, addr, ptep);
 		return;
 	}

arch/arm64/mm/kasan_init.c

@@ -44,92 +44,92 @@ static phys_addr_t __init kasan_alloc_zeroed_page(int node)
 	return __pa(p);
 }
 
-static pte_t *__init kasan_pte_offset(pmd_t *pmd, unsigned long addr, int node,
+static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
 				      bool early)
 {
-	if (pmd_none(*pmd)) {
+	if (pmd_none(READ_ONCE(*pmdp))) {
 		phys_addr_t pte_phys = early ? __pa_symbol(kasan_zero_pte)
 					     : kasan_alloc_zeroed_page(node);
-		__pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
+		__pmd_populate(pmdp, pte_phys, PMD_TYPE_TABLE);
 	}
 
-	return early ? pte_offset_kimg(pmd, addr)
-		     : pte_offset_kernel(pmd, addr);
+	return early ? pte_offset_kimg(pmdp, addr)
+		     : pte_offset_kernel(pmdp, addr);
 }
 
-static pmd_t *__init kasan_pmd_offset(pud_t *pud, unsigned long addr, int node,
+static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
 				      bool early)
 {
-	if (pud_none(*pud)) {
+	if (pud_none(READ_ONCE(*pudp))) {
 		phys_addr_t pmd_phys = early ? __pa_symbol(kasan_zero_pmd)
 					     : kasan_alloc_zeroed_page(node);
-		__pud_populate(pud, pmd_phys, PMD_TYPE_TABLE);
+		__pud_populate(pudp, pmd_phys, PMD_TYPE_TABLE);
 	}
 
-	return early ? pmd_offset_kimg(pud, addr) : pmd_offset(pud, addr);
+	return early ? pmd_offset_kimg(pudp, addr) : pmd_offset(pudp, addr);
 }
 
-static pud_t *__init kasan_pud_offset(pgd_t *pgd, unsigned long addr, int node,
+static pud_t *__init kasan_pud_offset(pgd_t *pgdp, unsigned long addr, int node,
 				      bool early)
 {
-	if (pgd_none(*pgd)) {
+	if (pgd_none(READ_ONCE(*pgdp))) {
 		phys_addr_t pud_phys = early ? __pa_symbol(kasan_zero_pud)
 					     : kasan_alloc_zeroed_page(node);
-		__pgd_populate(pgd, pud_phys, PMD_TYPE_TABLE);
+		__pgd_populate(pgdp, pud_phys, PMD_TYPE_TABLE);
 	}
 
-	return early ? pud_offset_kimg(pgd, addr) : pud_offset(pgd, addr);
+	return early ? pud_offset_kimg(pgdp, addr) : pud_offset(pgdp, addr);
 }
 
-static void __init kasan_pte_populate(pmd_t *pmd, unsigned long addr,
+static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 				      unsigned long end, int node, bool early)
 {
 	unsigned long next;
-	pte_t *pte = kasan_pte_offset(pmd, addr, node, early);
+	pte_t *ptep = kasan_pte_offset(pmdp, addr, node, early);
 
 	do {
 		phys_addr_t page_phys = early ? __pa_symbol(kasan_zero_page)
 					      : kasan_alloc_zeroed_page(node);
 		next = addr + PAGE_SIZE;
-		set_pte(pte, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
-	} while (pte++, addr = next, addr != end && pte_none(*pte));
+		set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
+	} while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
 }
 
-static void __init kasan_pmd_populate(pud_t *pud, unsigned long addr,
+static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
 				      unsigned long end, int node, bool early)
 {
 	unsigned long next;
-	pmd_t *pmd = kasan_pmd_offset(pud, addr, node, early);
+	pmd_t *pmdp = kasan_pmd_offset(pudp, addr, node, early);
 
 	do {
 		next = pmd_addr_end(addr, end);
-		kasan_pte_populate(pmd, addr, next, node, early);
-	} while (pmd++, addr = next, addr != end && pmd_none(*pmd));
+		kasan_pte_populate(pmdp, addr, next, node, early);
+	} while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
 }
 
-static void __init kasan_pud_populate(pgd_t *pgd, unsigned long addr,
+static void __init kasan_pud_populate(pgd_t *pgdp, unsigned long addr,
 				      unsigned long end, int node, bool early)
 {
 	unsigned long next;
-	pud_t *pud = kasan_pud_offset(pgd, addr, node, early);
+	pud_t *pudp = kasan_pud_offset(pgdp, addr, node, early);
 
 	do {
 		next = pud_addr_end(addr, end);
-		kasan_pmd_populate(pud, addr, next, node, early);
-	} while (pud++, addr = next, addr != end && pud_none(*pud));
+		kasan_pmd_populate(pudp, addr, next, node, early);
+	} while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
 }
 
 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
 				      int node, bool early)
 {
 	unsigned long next;
-	pgd_t *pgd;
+	pgd_t *pgdp;
 
-	pgd = pgd_offset_k(addr);
+	pgdp = pgd_offset_k(addr);
 	do {
 		next = pgd_addr_end(addr, end);
-		kasan_pud_populate(pgd, addr, next, node, early);
-	} while (pgd++, addr = next, addr != end);
+		kasan_pud_populate(pgdp, addr, next, node, early);
+	} while (pgdp++, addr = next, addr != end);
 }
 
 /* The early shadow maps everything to a single page of zeroes */
@@ -155,14 +155,14 @@ static void __init kasan_map_populate(unsigned long start, unsigned long end,
  */
 void __init kasan_copy_shadow(pgd_t *pgdir)
 {
-	pgd_t *pgd, *pgd_new, *pgd_end;
+	pgd_t *pgdp, *pgdp_new, *pgdp_end;
 
-	pgd = pgd_offset_k(KASAN_SHADOW_START);
-	pgd_end = pgd_offset_k(KASAN_SHADOW_END);
-	pgd_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
+	pgdp = pgd_offset_k(KASAN_SHADOW_START);
+	pgdp_end = pgd_offset_k(KASAN_SHADOW_END);
+	pgdp_new = pgd_offset_raw(pgdir, KASAN_SHADOW_START);
 	do {
-		set_pgd(pgd_new, *pgd);
-	} while (pgd++, pgd_new++, pgd != pgd_end);
+		set_pgd(pgdp_new, READ_ONCE(*pgdp));
+	} while (pgdp++, pgdp_new++, pgdp != pgdp_end);
 }
 
 static void __init clear_pgds(unsigned long start,

arch/arm64/mm/pageattr.c

@@ -29,7 +29,7 @@ static int change_page_range(pte_t *ptep, pgtable_t token, unsigned long addr,
 			void *data)
 {
 	struct page_change_data *cdata = data;
-	pte_t pte = *ptep;
+	pte_t pte = READ_ONCE(*ptep);
 
 	pte = clear_pte_bit(pte, cdata->clear_mask);
 	pte = set_pte_bit(pte, cdata->set_mask);
@@ -156,30 +156,32 @@ void __kernel_map_pages(struct page *page, int numpages, int enable)
  */
 bool kernel_page_present(struct page *page)
 {
-	pgd_t *pgd;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
+	pgd_t *pgdp;
+	pud_t *pudp, pud;
+	pmd_t *pmdp, pmd;
+	pte_t *ptep;
 	unsigned long addr = (unsigned long)page_address(page);
 
-	pgd = pgd_offset_k(addr);
-	if (pgd_none(*pgd))
+	pgdp = pgd_offset_k(addr);
+	if (pgd_none(READ_ONCE(*pgdp)))
 		return false;
 
-	pud = pud_offset(pgd, addr);
-	if (pud_none(*pud))
+	pudp = pud_offset(pgdp, addr);
+	pud = READ_ONCE(*pudp);
+	if (pud_none(pud))
 		return false;
-	if (pud_sect(*pud))
+	if (pud_sect(pud))
 		return true;
 
-	pmd = pmd_offset(pud, addr);
-	if (pmd_none(*pmd))
+	pmdp = pmd_offset(pudp, addr);
+	pmd = READ_ONCE(*pmdp);
+	if (pmd_none(pmd))
 		return false;
-	if (pmd_sect(*pmd))
+	if (pmd_sect(pmd))
 		return true;
 
-	pte = pte_offset_kernel(pmd, addr);
-	return pte_valid(*pte);
+	ptep = pte_offset_kernel(pmdp, addr);
+	return pte_valid(READ_ONCE(*ptep));
 }
 #endif /* CONFIG_HIBERNATION */
 #endif /* CONFIG_DEBUG_PAGEALLOC */