* [PATCH V3 1/4] arm64/mm: Use pmdp_get() for PMD accesses
2026-09-24 6:22 [PATCH V3 0/4] arm64/mm: Convert pgtable READ_ONCE() as pxdp_get() Anshuman Khandual
@ 2026-09-24 6:22 ` Anshuman Khandual
2026-09-24 12:09 ` Ryan Roberts
2026-09-24 6:22 ` [PATCH V3 2/4] arm64/mm: Use pudp_get() for PUD accesses Anshuman Khandual
` (2 subsequent siblings)
3 siblings, 1 reply; 9+ messages in thread
From: Anshuman Khandual @ 2026-09-24 6:22 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Anshuman Khandual, Catalin Marinas, Will Deacon, Ryan Roberts,
Mark Rutland, Lorenzo Stoakes, Andrew Morton, David Hildenbrand,
Mike Rapoport, Linu Cherian, linux-kernel, linux-mm, kasan-dev
Replace READ_ONCE() with pmdp_get() for PMD accesses in preparation for
supporting both D64 and D128 translation table formats.
READ_ONCE() cannot currently be used for 128-bit page table entries on
arm64 because it does not provide the required 128-bit single-copy
atomicity, causing builds to fail for accesses wider than 64 bits.
Although LDP/STP provide the required atomicity when FEAT_LSE is
available (as required by FEAT_D128), extending READ_ONCE() to support
128-bit accesses is undesirable. READ_ONCE() is a general-purpose API,
so doing so could encourage other 128-bit users that would either fail
to build in configurations without D128 support or, if D128 becomes a
runtime option, silently permit tearing on systems without the required
hardware support.
Instead, standardize PMD accesses on the existing page-table helpers.
These can be overridden on arm64 to provide 128-bit single-copy
atomicity when required.
For now override pmdp_get() which is same as the generic memory default
to avoid build dependency problem for callers in header <asm/pgtable.h>.
No functional change intended.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kasan-dev@googlegroups.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V3
- Added platform override for pmdp_get()
- Replaced READ_ONCE() in pmdp_test_and_clear_young()
arch/arm64/include/asm/pgtable.h | 11 +++++++++--
arch/arm64/mm/fault.c | 2 +-
arch/arm64/mm/fixmap.c | 2 +-
arch/arm64/mm/hugetlbpage.c | 2 +-
arch/arm64/mm/kasan_init.c | 4 ++--
arch/arm64/mm/mmu.c | 22 +++++++++++-----------
arch/arm64/mm/pageattr.c | 2 +-
arch/arm64/mm/trans_pgd.c | 2 +-
8 files changed, 27 insertions(+), 20 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 763c5a411d64..9ad2d03e86ad 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -84,6 +84,12 @@ static inline void arch_leave_lazy_mmu_mode(void)
arch_flush_lazy_mmu_mode();
}
+#define pmdp_get pmdp_get
+static inline pmd_t pmdp_get(pmd_t *pmdp)
+{
+ return READ_ONCE(*pmdp);
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
@@ -811,7 +817,8 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
}
/* Find an entry in the third-level page table. */
-#define pte_offset_phys(dir,addr) (pmd_page_paddr(READ_ONCE(*(dir))) + pte_index(addr) * sizeof(pte_t))
+#define pte_offset_phys(dir, addr) (pmd_page_paddr(pmdp_get(dir)) + \
+ pte_index(addr) * sizeof(pte_t))
#define pte_set_fixmap(addr) ((pte_t *)set_fixmap_offset(FIX_PTE, addr))
#define pte_set_fixmap_offset(pmd, addr) pte_set_fixmap(pte_offset_phys(pmd, addr))
@@ -1291,7 +1298,7 @@ static inline bool pmdp_test_and_clear_young(struct vm_area_struct *vma,
unsigned long address, pmd_t *pmdp)
{
/* Operation applies to PMD table entry only if FEAT_HAFT is enabled */
- VM_WARN_ON(pmd_table(READ_ONCE(*pmdp)) && !system_supports_haft());
+ VM_WARN_ON(pmd_table(pmdp_get(pmdp)) && !system_supports_haft());
return __ptep_test_and_clear_young(vma, address, (pte_t *)pmdp);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 2cecf6ba6df7..2757ee0c4300 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -188,7 +188,7 @@ static void show_pte(unsigned long addr)
break;
pmdp = pmd_offset_lockless(pudp, pud, addr);
- pmd = READ_ONCE(*pmdp);
+ pmd = pmdp_get(pmdp);
ptval_to_str(pxd_str, pmd_val(pmd));
pr_cont(", pmd=%s", pxd_str);
if (pmd_none(pmd) || pmd_bad(pmd))
diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
index f66a0016dd02..3cdac8021d4f 100644
--- a/arch/arm64/mm/fixmap.c
+++ b/arch/arm64/mm/fixmap.c
@@ -42,7 +42,7 @@ static inline pte_t *fixmap_pte(unsigned long addr)
static void __init early_fixmap_init_pte(pmd_t *pmdp, unsigned long addr)
{
- pmd_t pmd = READ_ONCE(*pmdp);
+ pmd_t pmd = pmdp_get(pmdp);
pte_t *ptep;
if (pmd_none(pmd)) {
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 8e799c1fe0aa..cdaa4500faf9 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -304,7 +304,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
addr &= CONT_PMD_MASK;
pmdp = pmd_offset(pudp, addr);
- pmd = READ_ONCE(*pmdp);
+ pmd = pmdp_get(pmdp);
if (!(sz == PMD_SIZE || sz == CONT_PMD_SIZE) &&
pmd_none(pmd))
return NULL;
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 45fbdce684c8..7ca833c5de5e 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -62,7 +62,7 @@ static phys_addr_t __init kasan_alloc_raw_page(int node)
static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
bool early)
{
- if (pmd_none(READ_ONCE(*pmdp))) {
+ if (pmd_none(pmdp_get(pmdp))) {
phys_addr_t pte_phys = early ?
__pa_symbol(kasan_early_shadow_pte)
: kasan_alloc_zeroed_page(node);
@@ -138,7 +138,7 @@ static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
do {
next = pmd_addr_end(addr, end);
kasan_pte_populate(pmdp, addr, next, node, early);
- } while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
+ } while (pmdp++, addr = next, addr != end && pmd_none(pmdp_get(pmdp)));
}
static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index e589fb00d1e3..95621913679e 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -200,7 +200,7 @@ static int alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr,
int flags)
{
unsigned long next;
- pmd_t pmd = READ_ONCE(*pmdp);
+ pmd_t pmd = pmdp_get(pmdp);
pte_t *ptep;
BUG_ON(pmd_leaf(pmd));
@@ -257,7 +257,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
unsigned long next;
do {
- pmd_t old_pmd = READ_ONCE(*pmdp);
+ pmd_t old_pmd = pmdp_get(pmdp);
next = pmd_addr_end(addr, end);
@@ -272,7 +272,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
* only allow updates to the permission attributes.
*/
BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),
- READ_ONCE(pmd_val(*pmdp))));
+ pmd_val(pmdp_get(pmdp))));
} else {
int ret;
@@ -282,7 +282,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
return ret;
VM_WARN_ON_ONCE(pmd_val(old_pmd) != 0 &&
- pmd_val(old_pmd) != READ_ONCE(pmd_val(*pmdp)));
+ pmd_val(old_pmd) != pmd_val(pmdp_get(pmdp)));
}
phys += next - addr;
} while (pmdp++, addr = next, addr != end);
@@ -293,7 +293,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
static bool pmd_range_has_valid_noncont(pmd_t *pmdp)
{
for (int i = 0; i < CONT_PMDS; i++) {
- pte_t pte = pmd_pte(READ_ONCE(pmdp[i]));
+ pte_t pte = pmd_pte(pmdp_get(pmdp + i));
if (pte_valid(pte) && !pte_cont(pte))
return true;
@@ -1553,7 +1553,7 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
do {
next = pmd_addr_end(addr, end);
pmdp = pmd_offset(pudp, addr);
- pmd = READ_ONCE(*pmdp);
+ pmd = pmdp_get(pmdp);
if (pmd_none(pmd))
continue;
@@ -1708,7 +1708,7 @@ static void free_empty_pmd_table(pud_t *pudp, unsigned long addr,
do {
next = pmd_addr_end(addr, end);
pmdp = pmd_offset(pudp, addr);
- pmd = READ_ONCE(*pmdp);
+ pmd = pmdp_get(pmdp);
if (pmd_none(pmd))
continue;
@@ -1729,7 +1729,7 @@ static void free_empty_pmd_table(pud_t *pudp, unsigned long addr,
*/
pmdp = pmd_offset(pudp, 0UL);
for (i = 0; i < PTRS_PER_PMD; i++) {
- if (!pmd_none(READ_ONCE(pmdp[i])))
+ if (!pmd_none(pmdp_get(pmdp + i)))
return;
}
@@ -1881,7 +1881,7 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), mk_pmd_sect_prot(prot));
/* Only allow permission changes for now */
- if (!pgattr_change_is_safe(READ_ONCE(pmd_val(*pmdp)),
+ if (!pgattr_change_is_safe(pmd_val(pmdp_get(pmdp)),
pmd_val(new_pmd)))
return 0;
@@ -1906,7 +1906,7 @@ int pud_clear_huge(pud_t *pudp)
int pmd_clear_huge(pmd_t *pmdp)
{
- if (!pmd_leaf(READ_ONCE(*pmdp)))
+ if (!pmd_leaf(pmdp_get(pmdp)))
return 0;
pmd_clear(pmdp);
return 1;
@@ -1917,7 +1917,7 @@ int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
pte_t *table;
pmd_t pmd;
- pmd = READ_ONCE(*pmdp);
+ pmd = pmdp_get(pmdp);
if (!pmd_table(pmd)) {
VM_WARN_ON(1);
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index bbe98ac9ad8c..0ca07bd5ded9 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -414,7 +414,7 @@ bool kernel_page_present(struct page *page)
return pud_valid(pud);
pmdp = pmd_offset(pudp, addr);
- pmd = READ_ONCE(*pmdp);
+ pmd = pmdp_get(pmdp);
if (pmd_none(pmd))
return false;
if (pmd_leaf(pmd))
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index cca9706a875c..b27b2d2c20c3 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c
@@ -74,7 +74,7 @@ static int copy_pmd(struct trans_pgd_info *info, pud_t *dst_pudp,
src_pmdp = pmd_offset(src_pudp, start);
do {
- pmd_t pmd = READ_ONCE(*src_pmdp);
+ pmd_t pmd = pmdp_get(src_pmdp);
next = pmd_addr_end(addr, end);
if (pmd_none(pmd))
--
2.43.0
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH V3 1/4] arm64/mm: Use pmdp_get() for PMD accesses
2026-09-24 6:22 ` [PATCH V3 1/4] arm64/mm: Use pmdp_get() for PMD accesses Anshuman Khandual
@ 2026-09-24 12:09 ` Ryan Roberts
0 siblings, 0 replies; 9+ messages in thread
From: Ryan Roberts @ 2026-09-24 12:09 UTC (permalink / raw)
To: Anshuman Khandual, linux-arm-kernel
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Lorenzo Stoakes,
Andrew Morton, David Hildenbrand, Mike Rapoport, Linu Cherian,
linux-kernel, linux-mm, kasan-dev
On 24/09/2026 07:22, Anshuman Khandual wrote:
> Replace READ_ONCE() with pmdp_get() for PMD accesses in preparation for
> supporting both D64 and D128 translation table formats.
>
> READ_ONCE() cannot currently be used for 128-bit page table entries on
> arm64 because it does not provide the required 128-bit single-copy
> atomicity, causing builds to fail for accesses wider than 64 bits.
>
> Although LDP/STP provide the required atomicity when FEAT_LSE is
> available (as required by FEAT_D128), extending READ_ONCE() to support
> 128-bit accesses is undesirable. READ_ONCE() is a general-purpose API,
> so doing so could encourage other 128-bit users that would either fail
> to build in configurations without D128 support or, if D128 becomes a
> runtime option, silently permit tearing on systems without the required
> hardware support.
>
> Instead, standardize PMD accesses on the existing page-table helpers.
> These can be overridden on arm64 to provide 128-bit single-copy
> atomicity when required.
>
> For now override pmdp_get() which is same as the generic memory default
> to avoid build dependency problem for callers in header <asm/pgtable.h>.
>
> No functional change intended.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kasan-dev@googlegroups.com
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
> Changes in V3
>
> - Added platform override for pmdp_get()
> - Replaced READ_ONCE() in pmdp_test_and_clear_young()
>
> arch/arm64/include/asm/pgtable.h | 11 +++++++++--
> arch/arm64/mm/fault.c | 2 +-
> arch/arm64/mm/fixmap.c | 2 +-
> arch/arm64/mm/hugetlbpage.c | 2 +-
> arch/arm64/mm/kasan_init.c | 4 ++--
> arch/arm64/mm/mmu.c | 22 +++++++++++-----------
> arch/arm64/mm/pageattr.c | 2 +-
> arch/arm64/mm/trans_pgd.c | 2 +-
> 8 files changed, 27 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 763c5a411d64..9ad2d03e86ad 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -84,6 +84,12 @@ static inline void arch_leave_lazy_mmu_mode(void)
> arch_flush_lazy_mmu_mode();
> }
>
> +#define pmdp_get pmdp_get
> +static inline pmd_t pmdp_get(pmd_t *pmdp)
> +{
> + return READ_ONCE(*pmdp);
> +}
> +
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>
> @@ -811,7 +817,8 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
> }
>
> /* Find an entry in the third-level page table. */
> -#define pte_offset_phys(dir,addr) (pmd_page_paddr(READ_ONCE(*(dir))) + pte_index(addr) * sizeof(pte_t))
> +#define pte_offset_phys(dir, addr) (pmd_page_paddr(pmdp_get(dir)) + \
> + pte_index(addr) * sizeof(pte_t))
>
> #define pte_set_fixmap(addr) ((pte_t *)set_fixmap_offset(FIX_PTE, addr))
> #define pte_set_fixmap_offset(pmd, addr) pte_set_fixmap(pte_offset_phys(pmd, addr))
> @@ -1291,7 +1298,7 @@ static inline bool pmdp_test_and_clear_young(struct vm_area_struct *vma,
> unsigned long address, pmd_t *pmdp)
> {
> /* Operation applies to PMD table entry only if FEAT_HAFT is enabled */
> - VM_WARN_ON(pmd_table(READ_ONCE(*pmdp)) && !system_supports_haft());
> + VM_WARN_ON(pmd_table(pmdp_get(pmdp)) && !system_supports_haft());
> return __ptep_test_and_clear_young(vma, address, (pte_t *)pmdp);
> }
> #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG */
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 2cecf6ba6df7..2757ee0c4300 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -188,7 +188,7 @@ static void show_pte(unsigned long addr)
> break;
>
> pmdp = pmd_offset_lockless(pudp, pud, addr);
> - pmd = READ_ONCE(*pmdp);
> + pmd = pmdp_get(pmdp);
> ptval_to_str(pxd_str, pmd_val(pmd));
> pr_cont(", pmd=%s", pxd_str);
> if (pmd_none(pmd) || pmd_bad(pmd))
> diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
> index f66a0016dd02..3cdac8021d4f 100644
> --- a/arch/arm64/mm/fixmap.c
> +++ b/arch/arm64/mm/fixmap.c
> @@ -42,7 +42,7 @@ static inline pte_t *fixmap_pte(unsigned long addr)
>
> static void __init early_fixmap_init_pte(pmd_t *pmdp, unsigned long addr)
> {
> - pmd_t pmd = READ_ONCE(*pmdp);
> + pmd_t pmd = pmdp_get(pmdp);
> pte_t *ptep;
>
> if (pmd_none(pmd)) {
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 8e799c1fe0aa..cdaa4500faf9 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -304,7 +304,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
> addr &= CONT_PMD_MASK;
>
> pmdp = pmd_offset(pudp, addr);
> - pmd = READ_ONCE(*pmdp);
> + pmd = pmdp_get(pmdp);
> if (!(sz == PMD_SIZE || sz == CONT_PMD_SIZE) &&
> pmd_none(pmd))
> return NULL;
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 45fbdce684c8..7ca833c5de5e 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -62,7 +62,7 @@ static phys_addr_t __init kasan_alloc_raw_page(int node)
> static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
> bool early)
> {
> - if (pmd_none(READ_ONCE(*pmdp))) {
> + if (pmd_none(pmdp_get(pmdp))) {
> phys_addr_t pte_phys = early ?
> __pa_symbol(kasan_early_shadow_pte)
> : kasan_alloc_zeroed_page(node);
> @@ -138,7 +138,7 @@ static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
> do {
> next = pmd_addr_end(addr, end);
> kasan_pte_populate(pmdp, addr, next, node, early);
> - } while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)));
> + } while (pmdp++, addr = next, addr != end && pmd_none(pmdp_get(pmdp)));
> }
>
> static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index e589fb00d1e3..95621913679e 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -200,7 +200,7 @@ static int alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr,
> int flags)
> {
> unsigned long next;
> - pmd_t pmd = READ_ONCE(*pmdp);
> + pmd_t pmd = pmdp_get(pmdp);
> pte_t *ptep;
>
> BUG_ON(pmd_leaf(pmd));
> @@ -257,7 +257,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
> unsigned long next;
>
> do {
> - pmd_t old_pmd = READ_ONCE(*pmdp);
> + pmd_t old_pmd = pmdp_get(pmdp);
>
> next = pmd_addr_end(addr, end);
>
> @@ -272,7 +272,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
> * only allow updates to the permission attributes.
> */
> BUG_ON(!pgattr_change_is_safe(pmd_val(old_pmd),
> - READ_ONCE(pmd_val(*pmdp))));
> + pmd_val(pmdp_get(pmdp))));
> } else {
> int ret;
>
> @@ -282,7 +282,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
> return ret;
>
> VM_WARN_ON_ONCE(pmd_val(old_pmd) != 0 &&
> - pmd_val(old_pmd) != READ_ONCE(pmd_val(*pmdp)));
> + pmd_val(old_pmd) != pmd_val(pmdp_get(pmdp)));
> }
> phys += next - addr;
> } while (pmdp++, addr = next, addr != end);
> @@ -293,7 +293,7 @@ static int init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end,
> static bool pmd_range_has_valid_noncont(pmd_t *pmdp)
> {
> for (int i = 0; i < CONT_PMDS; i++) {
> - pte_t pte = pmd_pte(READ_ONCE(pmdp[i]));
> + pte_t pte = pmd_pte(pmdp_get(pmdp + i));
>
> if (pte_valid(pte) && !pte_cont(pte))
> return true;
> @@ -1553,7 +1553,7 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
> do {
> next = pmd_addr_end(addr, end);
> pmdp = pmd_offset(pudp, addr);
> - pmd = READ_ONCE(*pmdp);
> + pmd = pmdp_get(pmdp);
> if (pmd_none(pmd))
> continue;
>
> @@ -1708,7 +1708,7 @@ static void free_empty_pmd_table(pud_t *pudp, unsigned long addr,
> do {
> next = pmd_addr_end(addr, end);
> pmdp = pmd_offset(pudp, addr);
> - pmd = READ_ONCE(*pmdp);
> + pmd = pmdp_get(pmdp);
> if (pmd_none(pmd))
> continue;
>
> @@ -1729,7 +1729,7 @@ static void free_empty_pmd_table(pud_t *pudp, unsigned long addr,
> */
> pmdp = pmd_offset(pudp, 0UL);
> for (i = 0; i < PTRS_PER_PMD; i++) {
> - if (!pmd_none(READ_ONCE(pmdp[i])))
> + if (!pmd_none(pmdp_get(pmdp + i)))
> return;
> }
>
> @@ -1881,7 +1881,7 @@ int pmd_set_huge(pmd_t *pmdp, phys_addr_t phys, pgprot_t prot)
> pmd_t new_pmd = pfn_pmd(__phys_to_pfn(phys), mk_pmd_sect_prot(prot));
>
> /* Only allow permission changes for now */
> - if (!pgattr_change_is_safe(READ_ONCE(pmd_val(*pmdp)),
> + if (!pgattr_change_is_safe(pmd_val(pmdp_get(pmdp)),
> pmd_val(new_pmd)))
> return 0;
>
> @@ -1906,7 +1906,7 @@ int pud_clear_huge(pud_t *pudp)
>
> int pmd_clear_huge(pmd_t *pmdp)
> {
> - if (!pmd_leaf(READ_ONCE(*pmdp)))
> + if (!pmd_leaf(pmdp_get(pmdp)))
> return 0;
> pmd_clear(pmdp);
> return 1;
> @@ -1917,7 +1917,7 @@ int pmd_free_pte_page(pmd_t *pmdp, unsigned long addr)
> pte_t *table;
> pmd_t pmd;
>
> - pmd = READ_ONCE(*pmdp);
> + pmd = pmdp_get(pmdp);
>
> if (!pmd_table(pmd)) {
> VM_WARN_ON(1);
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index bbe98ac9ad8c..0ca07bd5ded9 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -414,7 +414,7 @@ bool kernel_page_present(struct page *page)
> return pud_valid(pud);
>
> pmdp = pmd_offset(pudp, addr);
> - pmd = READ_ONCE(*pmdp);
> + pmd = pmdp_get(pmdp);
> if (pmd_none(pmd))
> return false;
> if (pmd_leaf(pmd))
> diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
> index cca9706a875c..b27b2d2c20c3 100644
> --- a/arch/arm64/mm/trans_pgd.c
> +++ b/arch/arm64/mm/trans_pgd.c
> @@ -74,7 +74,7 @@ static int copy_pmd(struct trans_pgd_info *info, pud_t *dst_pudp,
>
> src_pmdp = pmd_offset(src_pudp, start);
> do {
> - pmd_t pmd = READ_ONCE(*src_pmdp);
> + pmd_t pmd = pmdp_get(src_pmdp);
>
> next = pmd_addr_end(addr, end);
> if (pmd_none(pmd))
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH V3 2/4] arm64/mm: Use pudp_get() for PUD accesses
2026-09-24 6:22 [PATCH V3 0/4] arm64/mm: Convert pgtable READ_ONCE() as pxdp_get() Anshuman Khandual
2026-09-24 6:22 ` [PATCH V3 1/4] arm64/mm: Use pmdp_get() for PMD accesses Anshuman Khandual
@ 2026-09-24 6:22 ` Anshuman Khandual
2026-09-24 12:10 ` Ryan Roberts
2026-09-24 6:22 ` [PATCH V3 3/4] arm64/mm: Use p4dp_get() for P4D accesses Anshuman Khandual
2026-09-24 6:22 ` [PATCH V3 4/4] arm64/mm: Use pgdp_get() for PGD accesses Anshuman Khandual
3 siblings, 1 reply; 9+ messages in thread
From: Anshuman Khandual @ 2026-09-24 6:22 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Anshuman Khandual, Catalin Marinas, Will Deacon, Ryan Roberts,
Mark Rutland, Lorenzo Stoakes, Andrew Morton, David Hildenbrand,
Mike Rapoport, Linu Cherian, linux-kernel, linux-mm, kasan-dev
Replace READ_ONCE() with pudp_get() for PUD accesses in preparation for
supporting both D64 and D128 translation table formats.
READ_ONCE() cannot currently be used for 128-bit page table entries on
arm64 because it does not provide the required 128-bit single-copy
atomicity, causing builds to fail for accesses wider than 64 bits.
Although LDP/STP provide the required atomicity when FEAT_LSE is available
(as required by FEAT_D128), extending READ_ONCE() to support 128-bit
accesses is undesirable. READ_ONCE() is a general-purpose API, so doing so
could encourage other 128-bit users that would either fail to build in
configurations without D128 support or, if D128 becomes a runtime option,
silently permit tearing on systems without the required hardware support.
Instead, standardize PUD accesses on the existing page-table helpers. These
can be overridden on arm64 to provide 128-bit single-copy atomicity when
required.
For now override pudp_get() which is same as the generic memory default in
order to be consistent with similar helpers.
No functional change intended.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kasan-dev@googlegroups.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V3
- Added platform override for pudp_get()
arch/arm64/include/asm/pgtable.h | 9 ++++++++-
arch/arm64/mm/fault.c | 2 +-
arch/arm64/mm/fixmap.c | 2 +-
arch/arm64/mm/hugetlbpage.c | 4 ++--
arch/arm64/mm/kasan_init.c | 4 ++--
arch/arm64/mm/mmu.c | 20 ++++++++++----------
arch/arm64/mm/pageattr.c | 2 +-
arch/arm64/mm/trans_pgd.c | 4 ++--
8 files changed, 27 insertions(+), 20 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 9ad2d03e86ad..b46930f844a2 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -90,6 +90,12 @@ static inline pmd_t pmdp_get(pmd_t *pmdp)
return READ_ONCE(*pmdp);
}
+#define pudp_get pudp_get
+static inline pud_t pudp_get(pud_t *pudp)
+{
+ return READ_ONCE(*pudp);
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
@@ -879,7 +885,8 @@ static inline pmd_t *pud_pgtable(pud_t pud)
}
/* Find an entry in the second-level page table. */
-#define pmd_offset_phys(dir, addr) (pud_page_paddr(READ_ONCE(*(dir))) + pmd_index(addr) * sizeof(pmd_t))
+#define pmd_offset_phys(dir, addr) (pud_page_paddr(pudp_get(dir)) + \
+ pmd_index(addr) * sizeof(pmd_t))
#define pmd_set_fixmap(addr) ((pmd_t *)set_fixmap_offset(FIX_PMD, addr))
#define pmd_set_fixmap_offset(pud, addr) pmd_set_fixmap(pmd_offset_phys(pud, addr))
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 2757ee0c4300..435e2e14c070 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -181,7 +181,7 @@ static void show_pte(unsigned long addr)
break;
pudp = pud_offset_lockless(p4dp, p4d, addr);
- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
ptval_to_str(pxd_str, pud_val(pud));
pr_cont(", pud=%s", pxd_str);
if (pud_none(pud) || pud_bad(pud))
diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
index 3cdac8021d4f..d9a870836faf 100644
--- a/arch/arm64/mm/fixmap.c
+++ b/arch/arm64/mm/fixmap.c
@@ -56,7 +56,7 @@ static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
unsigned long end)
{
unsigned long next;
- pud_t pud = READ_ONCE(*pudp);
+ pud_t pud = pudp_get(pudp);
pmd_t *pmdp;
if (pud_none(pud))
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index cdaa4500faf9..c9ad5e75b073 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -262,7 +262,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
WARN_ON(addr & (sz - 1));
ptep = pte_alloc_huge(mm, pmdp, addr);
} else if (sz == PMD_SIZE) {
- if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp)))
+ if (want_pmd_share(vma, addr) && pud_none(pudp_get(pudp)))
ptep = huge_pmd_share(mm, vma, addr, pudp);
else
ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
@@ -292,7 +292,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
return NULL;
pudp = pud_offset(p4dp, addr);
- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
if (sz != PUD_SIZE && pud_none(pud))
return NULL;
/* hugepage or swap? */
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 7ca833c5de5e..aad29bcc7622 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -76,7 +76,7 @@ static pte_t *__init kasan_pte_offset(pmd_t *pmdp, 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(READ_ONCE(*pudp))) {
+ if (pud_none(pudp_get(pudp))) {
phys_addr_t pmd_phys = early ?
__pa_symbol(kasan_early_shadow_pmd)
: kasan_alloc_zeroed_page(node);
@@ -150,7 +150,7 @@ static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
do {
next = pud_addr_end(addr, end);
kasan_pmd_populate(pudp, addr, next, node, early);
- } while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
+ } while (pudp++, addr = next, addr != end && pud_none(pudp_get(pudp)));
}
static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 95621913679e..22efaee79293 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -309,7 +309,7 @@ static int alloc_init_cont_pmd(pud_t *pudp, unsigned long addr,
{
int ret;
unsigned long next;
- pud_t pud = READ_ONCE(*pudp);
+ pud_t pud = pudp_get(pudp);
pmd_t *pmdp;
/*
@@ -390,7 +390,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
}
do {
- pud_t old_pud = READ_ONCE(*pudp);
+ pud_t old_pud = pudp_get(pudp);
next = pud_addr_end(addr, end);
@@ -408,7 +408,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
* only allow updates to the permission attributes.
*/
BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),
- READ_ONCE(pud_val(*pudp))));
+ pud_val(pudp_get(pudp))));
} else {
ret = alloc_init_cont_pmd(pudp, addr, next, phys, prot,
pgtable_alloc, flags);
@@ -416,7 +416,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
goto out;
VM_WARN_ON_ONCE(pud_val(old_pud) != 0 &&
- pud_val(old_pud) != READ_ONCE(pud_val(*pudp)));
+ pud_val(old_pud) != pud_val(pudp_get(pudp)));
}
phys += next - addr;
} while (pudp++, addr = next, addr != end);
@@ -1591,7 +1591,7 @@ static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
do {
next = pud_addr_end(addr, end);
pudp = pud_offset(p4dp, addr);
- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
if (pud_none(pud))
continue;
@@ -1748,7 +1748,7 @@ static void free_empty_pud_table(p4d_t *p4dp, unsigned long addr,
do {
next = pud_addr_end(addr, end);
pudp = pud_offset(p4dp, addr);
- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
if (pud_none(pud))
continue;
@@ -1769,7 +1769,7 @@ static void free_empty_pud_table(p4d_t *p4dp, unsigned long addr,
*/
pudp = pud_offset(p4dp, 0UL);
for (i = 0; i < PTRS_PER_PUD; i++) {
- if (!pud_none(READ_ONCE(pudp[i])))
+ if (!pud_none(pudp_get(pudp + i)))
return;
}
@@ -1867,7 +1867,7 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));
/* Only allow permission changes for now */
- if (!pgattr_change_is_safe(READ_ONCE(pud_val(*pudp)),
+ if (!pgattr_change_is_safe(pud_val(pudp_get(pudp)),
pud_val(new_pud)))
return 0;
@@ -1898,7 +1898,7 @@ void p4d_clear_huge(p4d_t *p4dp)
int pud_clear_huge(pud_t *pudp)
{
- if (!pud_leaf(READ_ONCE(*pudp)))
+ if (!pud_leaf(pudp_get(pudp)))
return 0;
pud_clear(pudp);
return 1;
@@ -1938,7 +1938,7 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
pud_t pud;
unsigned long next, end;
- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
if (!pud_table(pud)) {
VM_WARN_ON(1);
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 0ca07bd5ded9..07b2fa4de57f 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -407,7 +407,7 @@ bool kernel_page_present(struct page *page)
return false;
pudp = pud_offset(p4dp, addr);
- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
if (pud_none(pud))
return false;
if (pud_leaf(pud))
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index b27b2d2c20c3..d119119455f1 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c
@@ -64,7 +64,7 @@ static int copy_pmd(struct trans_pgd_info *info, pud_t *dst_pudp,
unsigned long next;
unsigned long addr = start;
- if (pud_none(READ_ONCE(*dst_pudp))) {
+ if (pud_none(pudp_get(dst_pudp))) {
dst_pmdp = trans_alloc(info);
if (!dst_pmdp)
return -ENOMEM;
@@ -109,7 +109,7 @@ static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp,
src_pudp = pud_offset(src_p4dp, start);
do {
- pud_t pud = READ_ONCE(*src_pudp);
+ pud_t pud = pudp_get(src_pudp);
next = pud_addr_end(addr, end);
if (pud_none(pud))
--
2.43.0
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH V3 2/4] arm64/mm: Use pudp_get() for PUD accesses
2026-09-24 6:22 ` [PATCH V3 2/4] arm64/mm: Use pudp_get() for PUD accesses Anshuman Khandual
@ 2026-09-24 12:10 ` Ryan Roberts
0 siblings, 0 replies; 9+ messages in thread
From: Ryan Roberts @ 2026-09-24 12:10 UTC (permalink / raw)
To: Anshuman Khandual, linux-arm-kernel
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Lorenzo Stoakes,
Andrew Morton, David Hildenbrand, Mike Rapoport, Linu Cherian,
linux-kernel, linux-mm, kasan-dev
On 24/09/2026 07:22, Anshuman Khandual wrote:
> Replace READ_ONCE() with pudp_get() for PUD accesses in preparation for
> supporting both D64 and D128 translation table formats.
>
> READ_ONCE() cannot currently be used for 128-bit page table entries on
> arm64 because it does not provide the required 128-bit single-copy
> atomicity, causing builds to fail for accesses wider than 64 bits.
>
> Although LDP/STP provide the required atomicity when FEAT_LSE is available
> (as required by FEAT_D128), extending READ_ONCE() to support 128-bit
> accesses is undesirable. READ_ONCE() is a general-purpose API, so doing so
> could encourage other 128-bit users that would either fail to build in
> configurations without D128 support or, if D128 becomes a runtime option,
> silently permit tearing on systems without the required hardware support.
>
> Instead, standardize PUD accesses on the existing page-table helpers. These
> can be overridden on arm64 to provide 128-bit single-copy atomicity when
> required.
>
> For now override pudp_get() which is same as the generic memory default in
> order to be consistent with similar helpers.
>
> No functional change intended.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kasan-dev@googlegroups.com
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
> Changes in V3
>
> - Added platform override for pudp_get()
>
> arch/arm64/include/asm/pgtable.h | 9 ++++++++-
> arch/arm64/mm/fault.c | 2 +-
> arch/arm64/mm/fixmap.c | 2 +-
> arch/arm64/mm/hugetlbpage.c | 4 ++--
> arch/arm64/mm/kasan_init.c | 4 ++--
> arch/arm64/mm/mmu.c | 20 ++++++++++----------
> arch/arm64/mm/pageattr.c | 2 +-
> arch/arm64/mm/trans_pgd.c | 4 ++--
> 8 files changed, 27 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 9ad2d03e86ad..b46930f844a2 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -90,6 +90,12 @@ static inline pmd_t pmdp_get(pmd_t *pmdp)
> return READ_ONCE(*pmdp);
> }
>
> +#define pudp_get pudp_get
> +static inline pud_t pudp_get(pud_t *pudp)
> +{
> + return READ_ONCE(*pudp);
> +}
> +
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>
> @@ -879,7 +885,8 @@ static inline pmd_t *pud_pgtable(pud_t pud)
> }
>
> /* Find an entry in the second-level page table. */
> -#define pmd_offset_phys(dir, addr) (pud_page_paddr(READ_ONCE(*(dir))) + pmd_index(addr) * sizeof(pmd_t))
> +#define pmd_offset_phys(dir, addr) (pud_page_paddr(pudp_get(dir)) + \
> + pmd_index(addr) * sizeof(pmd_t))
>
> #define pmd_set_fixmap(addr) ((pmd_t *)set_fixmap_offset(FIX_PMD, addr))
> #define pmd_set_fixmap_offset(pud, addr) pmd_set_fixmap(pmd_offset_phys(pud, addr))
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 2757ee0c4300..435e2e14c070 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -181,7 +181,7 @@ static void show_pte(unsigned long addr)
> break;
>
> pudp = pud_offset_lockless(p4dp, p4d, addr);
> - pud = READ_ONCE(*pudp);
> + pud = pudp_get(pudp);
> ptval_to_str(pxd_str, pud_val(pud));
> pr_cont(", pud=%s", pxd_str);
> if (pud_none(pud) || pud_bad(pud))
> diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
> index 3cdac8021d4f..d9a870836faf 100644
> --- a/arch/arm64/mm/fixmap.c
> +++ b/arch/arm64/mm/fixmap.c
> @@ -56,7 +56,7 @@ static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
> unsigned long end)
> {
> unsigned long next;
> - pud_t pud = READ_ONCE(*pudp);
> + pud_t pud = pudp_get(pudp);
> pmd_t *pmdp;
>
> if (pud_none(pud))
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index cdaa4500faf9..c9ad5e75b073 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -262,7 +262,7 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
> WARN_ON(addr & (sz - 1));
> ptep = pte_alloc_huge(mm, pmdp, addr);
> } else if (sz == PMD_SIZE) {
> - if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp)))
> + if (want_pmd_share(vma, addr) && pud_none(pudp_get(pudp)))
> ptep = huge_pmd_share(mm, vma, addr, pudp);
> else
> ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
> @@ -292,7 +292,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
> return NULL;
>
> pudp = pud_offset(p4dp, addr);
> - pud = READ_ONCE(*pudp);
> + pud = pudp_get(pudp);
> if (sz != PUD_SIZE && pud_none(pud))
> return NULL;
> /* hugepage or swap? */
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 7ca833c5de5e..aad29bcc7622 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -76,7 +76,7 @@ static pte_t *__init kasan_pte_offset(pmd_t *pmdp, 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(READ_ONCE(*pudp))) {
> + if (pud_none(pudp_get(pudp))) {
> phys_addr_t pmd_phys = early ?
> __pa_symbol(kasan_early_shadow_pmd)
> : kasan_alloc_zeroed_page(node);
> @@ -150,7 +150,7 @@ static void __init kasan_pud_populate(p4d_t *p4dp, unsigned long addr,
> do {
> next = pud_addr_end(addr, end);
> kasan_pmd_populate(pudp, addr, next, node, early);
> - } while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)));
> + } while (pudp++, addr = next, addr != end && pud_none(pudp_get(pudp)));
> }
>
> static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 95621913679e..22efaee79293 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -309,7 +309,7 @@ static int alloc_init_cont_pmd(pud_t *pudp, unsigned long addr,
> {
> int ret;
> unsigned long next;
> - pud_t pud = READ_ONCE(*pudp);
> + pud_t pud = pudp_get(pudp);
> pmd_t *pmdp;
>
> /*
> @@ -390,7 +390,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
> }
>
> do {
> - pud_t old_pud = READ_ONCE(*pudp);
> + pud_t old_pud = pudp_get(pudp);
>
> next = pud_addr_end(addr, end);
>
> @@ -408,7 +408,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
> * only allow updates to the permission attributes.
> */
> BUG_ON(!pgattr_change_is_safe(pud_val(old_pud),
> - READ_ONCE(pud_val(*pudp))));
> + pud_val(pudp_get(pudp))));
> } else {
> ret = alloc_init_cont_pmd(pudp, addr, next, phys, prot,
> pgtable_alloc, flags);
> @@ -416,7 +416,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
> goto out;
>
> VM_WARN_ON_ONCE(pud_val(old_pud) != 0 &&
> - pud_val(old_pud) != READ_ONCE(pud_val(*pudp)));
> + pud_val(old_pud) != pud_val(pudp_get(pudp)));
> }
> phys += next - addr;
> } while (pudp++, addr = next, addr != end);
> @@ -1591,7 +1591,7 @@ static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
> do {
> next = pud_addr_end(addr, end);
> pudp = pud_offset(p4dp, addr);
> - pud = READ_ONCE(*pudp);
> + pud = pudp_get(pudp);
> if (pud_none(pud))
> continue;
>
> @@ -1748,7 +1748,7 @@ static void free_empty_pud_table(p4d_t *p4dp, unsigned long addr,
> do {
> next = pud_addr_end(addr, end);
> pudp = pud_offset(p4dp, addr);
> - pud = READ_ONCE(*pudp);
> + pud = pudp_get(pudp);
> if (pud_none(pud))
> continue;
>
> @@ -1769,7 +1769,7 @@ static void free_empty_pud_table(p4d_t *p4dp, unsigned long addr,
> */
> pudp = pud_offset(p4dp, 0UL);
> for (i = 0; i < PTRS_PER_PUD; i++) {
> - if (!pud_none(READ_ONCE(pudp[i])))
> + if (!pud_none(pudp_get(pudp + i)))
> return;
> }
>
> @@ -1867,7 +1867,7 @@ int pud_set_huge(pud_t *pudp, phys_addr_t phys, pgprot_t prot)
> pud_t new_pud = pfn_pud(__phys_to_pfn(phys), mk_pud_sect_prot(prot));
>
> /* Only allow permission changes for now */
> - if (!pgattr_change_is_safe(READ_ONCE(pud_val(*pudp)),
> + if (!pgattr_change_is_safe(pud_val(pudp_get(pudp)),
> pud_val(new_pud)))
> return 0;
>
> @@ -1898,7 +1898,7 @@ void p4d_clear_huge(p4d_t *p4dp)
>
> int pud_clear_huge(pud_t *pudp)
> {
> - if (!pud_leaf(READ_ONCE(*pudp)))
> + if (!pud_leaf(pudp_get(pudp)))
> return 0;
> pud_clear(pudp);
> return 1;
> @@ -1938,7 +1938,7 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
> pud_t pud;
> unsigned long next, end;
>
> - pud = READ_ONCE(*pudp);
> + pud = pudp_get(pudp);
>
> if (!pud_table(pud)) {
> VM_WARN_ON(1);
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 0ca07bd5ded9..07b2fa4de57f 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -407,7 +407,7 @@ bool kernel_page_present(struct page *page)
> return false;
>
> pudp = pud_offset(p4dp, addr);
> - pud = READ_ONCE(*pudp);
> + pud = pudp_get(pudp);
> if (pud_none(pud))
> return false;
> if (pud_leaf(pud))
> diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
> index b27b2d2c20c3..d119119455f1 100644
> --- a/arch/arm64/mm/trans_pgd.c
> +++ b/arch/arm64/mm/trans_pgd.c
> @@ -64,7 +64,7 @@ static int copy_pmd(struct trans_pgd_info *info, pud_t *dst_pudp,
> unsigned long next;
> unsigned long addr = start;
>
> - if (pud_none(READ_ONCE(*dst_pudp))) {
> + if (pud_none(pudp_get(dst_pudp))) {
> dst_pmdp = trans_alloc(info);
> if (!dst_pmdp)
> return -ENOMEM;
> @@ -109,7 +109,7 @@ static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp,
>
> src_pudp = pud_offset(src_p4dp, start);
> do {
> - pud_t pud = READ_ONCE(*src_pudp);
> + pud_t pud = pudp_get(src_pudp);
>
> next = pud_addr_end(addr, end);
> if (pud_none(pud))
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH V3 3/4] arm64/mm: Use p4dp_get() for P4D accesses
2026-09-24 6:22 [PATCH V3 0/4] arm64/mm: Convert pgtable READ_ONCE() as pxdp_get() Anshuman Khandual
2026-09-24 6:22 ` [PATCH V3 1/4] arm64/mm: Use pmdp_get() for PMD accesses Anshuman Khandual
2026-09-24 6:22 ` [PATCH V3 2/4] arm64/mm: Use pudp_get() for PUD accesses Anshuman Khandual
@ 2026-09-24 6:22 ` Anshuman Khandual
2026-09-24 12:10 ` Ryan Roberts
2026-09-24 6:22 ` [PATCH V3 4/4] arm64/mm: Use pgdp_get() for PGD accesses Anshuman Khandual
3 siblings, 1 reply; 9+ messages in thread
From: Anshuman Khandual @ 2026-09-24 6:22 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Anshuman Khandual, Catalin Marinas, Will Deacon, Ryan Roberts,
Mark Rutland, Lorenzo Stoakes, Andrew Morton, David Hildenbrand,
Mike Rapoport, Linu Cherian, linux-kernel, linux-mm, kasan-dev
Replace READ_ONCE() with p4dp_get() for P4D accesses in preparation for
supporting both D64 and D128 translation table formats.
READ_ONCE() cannot currently be used for 128-bit page table entries on
arm64 because it does not provide the required 128-bit single-copy
atomicity, causing builds to fail for accesses wider than 64 bits.
Although LDP/STP provide the required atomicity when FEAT_LSE is
available (as required by FEAT_D128), extending READ_ONCE() to support
128-bit accesses is undesirable. READ_ONCE() is a general-purpose API,
so doing so could encourage other 128-bit users that would either fail
to build in configurations without D128 support or, if D128 becomes a
runtime option, silently permit tearing on systems without the required
hardware support.
Instead, standardize P4D accesses on the existing page-table helpers.
These can be overridden on arm64 to provide 128-bit single-copy
atomicity when required.
For now override p4dp_get() which is same as the generic memory default
to avoid build dependency problem for callers in header <asm/pgtable.h>.
No functional change intended.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kasan-dev@googlegroups.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V3
- Added platform override for p4dp_get()
- Replaced READ_ONCE() in pud_offset_phys() and pud_offset()
arch/arm64/include/asm/pgtable.h | 10 ++++++++--
arch/arm64/mm/fault.c | 2 +-
arch/arm64/mm/fixmap.c | 2 +-
arch/arm64/mm/hugetlbpage.c | 2 +-
arch/arm64/mm/kasan_init.c | 4 ++--
arch/arm64/mm/mmu.c | 12 ++++++------
arch/arm64/mm/pageattr.c | 2 +-
arch/arm64/mm/trans_pgd.c | 4 ++--
8 files changed, 22 insertions(+), 16 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index b46930f844a2..f235f68a7518 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -96,6 +96,12 @@ static inline pud_t pudp_get(pud_t *pudp)
return READ_ONCE(*pudp);
}
+#define p4dp_get p4dp_get
+static inline p4d_t p4dp_get(p4d_t *p4dp)
+{
+ return READ_ONCE(*p4dp);
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
@@ -976,7 +982,7 @@ static inline phys_addr_t pud_offset_phys(p4d_t *p4dp, unsigned long addr)
{
VM_WARN_ON_ONCE(!pgtable_l4_enabled());
- return p4d_page_paddr(READ_ONCE(*p4dp)) + pud_index(addr) * sizeof(pud_t);
+ return p4d_page_paddr(p4dp_get(p4dp)) + pud_index(addr) * sizeof(pud_t);
}
static inline
@@ -990,7 +996,7 @@ pud_t *pud_offset_lockless(p4d_t *p4dp, p4d_t p4d, unsigned long addr)
static inline pud_t *pud_offset(p4d_t *p4dp, unsigned long addr)
{
- return pud_offset_lockless(p4dp, READ_ONCE(*p4dp), addr);
+ return pud_offset_lockless(p4dp, p4dp_get(p4dp), addr);
}
#define pud_offset pud_offset
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 435e2e14c070..a6afd8929a10 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -174,7 +174,7 @@ static void show_pte(unsigned long addr)
break;
p4dp = p4d_offset_lockless(pgdp, pgd, addr);
- p4d = READ_ONCE(*p4dp);
+ p4d = p4dp_get(p4dp);
ptval_to_str(pxd_str, p4d_val(p4d));
pr_cont(", p4d=%s", pxd_str);
if (p4d_none(p4d) || p4d_bad(p4d))
diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
index d9a870836faf..2a0fe0b0f771 100644
--- a/arch/arm64/mm/fixmap.c
+++ b/arch/arm64/mm/fixmap.c
@@ -74,7 +74,7 @@ static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr,
unsigned long end)
{
- p4d_t p4d = READ_ONCE(*p4dp);
+ p4d_t p4d = p4dp_get(p4dp);
pud_t *pudp;
if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) &&
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index c9ad5e75b073..5771bf49e1fe 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -288,7 +288,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
return NULL;
p4dp = p4d_offset(pgdp, addr);
- if (!p4d_present(READ_ONCE(*p4dp)))
+ if (!p4d_present(p4dp_get(p4dp)))
return NULL;
pudp = pud_offset(p4dp, addr);
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index aad29bcc7622..4dd8c1186471 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -89,7 +89,7 @@ static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node,
bool early)
{
- if (p4d_none(READ_ONCE(*p4dp))) {
+ if (p4d_none(p4dp_get(p4dp))) {
phys_addr_t pud_phys = early ?
__pa_symbol(kasan_early_shadow_pud)
: kasan_alloc_zeroed_page(node);
@@ -162,7 +162,7 @@ static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
do {
next = p4d_addr_end(addr, end);
kasan_pud_populate(p4dp, addr, next, node, early);
- } while (p4dp++, addr = next, addr != end && p4d_none(READ_ONCE(*p4dp)));
+ } while (p4dp++, addr = next, addr != end && p4d_none(p4dp_get(p4dp)));
}
static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 22efaee79293..83709d987e7c 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -367,7 +367,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
{
int ret = 0;
unsigned long next;
- p4d_t p4d = READ_ONCE(*p4dp);
+ p4d_t p4d = p4dp_get(p4dp);
pud_t *pudp;
if (p4d_none(p4d)) {
@@ -457,7 +457,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
}
do {
- p4d_t old_p4d = READ_ONCE(*p4dp);
+ p4d_t old_p4d = p4dp_get(p4dp);
next = p4d_addr_end(addr, end);
@@ -467,7 +467,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
goto out;
VM_WARN_ON_ONCE(p4d_val(old_p4d) != 0 &&
- p4d_val(old_p4d) != READ_ONCE(p4d_val(*p4dp)));
+ p4d_val(old_p4d) != (p4d_val(p4dp_get(p4dp))));
phys += next - addr;
} while (p4dp++, addr = next, addr != end);
@@ -1622,7 +1622,7 @@ static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr,
do {
next = p4d_addr_end(addr, end);
p4dp = p4d_offset(pgdp, addr);
- p4d = READ_ONCE(*p4dp);
+ p4d = p4dp_get(p4dp);
if (p4d_none(p4d))
continue;
@@ -1788,7 +1788,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr,
do {
next = p4d_addr_end(addr, end);
p4dp = p4d_offset(pgdp, addr);
- p4d = READ_ONCE(*p4dp);
+ p4d = p4dp_get(p4dp);
if (p4d_none(p4d))
continue;
@@ -1809,7 +1809,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr,
*/
p4dp = p4d_offset(pgdp, 0UL);
for (i = 0; i < PTRS_PER_P4D; i++) {
- if (!p4d_none(READ_ONCE(p4dp[i])))
+ if (!p4d_none(p4dp_get(p4dp + i)))
return;
}
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 07b2fa4de57f..826856ef64a8 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -403,7 +403,7 @@ bool kernel_page_present(struct page *page)
return false;
p4dp = p4d_offset(pgdp, addr);
- if (p4d_none(READ_ONCE(*p4dp)))
+ if (p4d_none(p4dp_get(p4dp)))
return false;
pudp = pud_offset(p4dp, addr);
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index d119119455f1..7afe2beca4ba 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c
@@ -99,7 +99,7 @@ static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp,
unsigned long next;
unsigned long addr = start;
- if (p4d_none(READ_ONCE(*dst_p4dp))) {
+ if (p4d_none(p4dp_get(dst_p4dp))) {
dst_pudp = trans_alloc(info);
if (!dst_pudp)
return -ENOMEM;
@@ -145,7 +145,7 @@ static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp,
src_p4dp = p4d_offset(src_pgdp, start);
do {
next = p4d_addr_end(addr, end);
- if (p4d_none(READ_ONCE(*src_p4dp)))
+ if (p4d_none(p4dp_get(src_p4dp)))
continue;
if (copy_pud(info, dst_p4dp, src_p4dp, addr, next))
return -ENOMEM;
--
2.43.0
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH V3 3/4] arm64/mm: Use p4dp_get() for P4D accesses
2026-09-24 6:22 ` [PATCH V3 3/4] arm64/mm: Use p4dp_get() for P4D accesses Anshuman Khandual
@ 2026-09-24 12:10 ` Ryan Roberts
0 siblings, 0 replies; 9+ messages in thread
From: Ryan Roberts @ 2026-09-24 12:10 UTC (permalink / raw)
To: Anshuman Khandual, linux-arm-kernel
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Lorenzo Stoakes,
Andrew Morton, David Hildenbrand, Mike Rapoport, Linu Cherian,
linux-kernel, linux-mm, kasan-dev
On 24/09/2026 07:22, Anshuman Khandual wrote:
> Replace READ_ONCE() with p4dp_get() for P4D accesses in preparation for
> supporting both D64 and D128 translation table formats.
>
> READ_ONCE() cannot currently be used for 128-bit page table entries on
> arm64 because it does not provide the required 128-bit single-copy
> atomicity, causing builds to fail for accesses wider than 64 bits.
>
> Although LDP/STP provide the required atomicity when FEAT_LSE is
> available (as required by FEAT_D128), extending READ_ONCE() to support
> 128-bit accesses is undesirable. READ_ONCE() is a general-purpose API,
> so doing so could encourage other 128-bit users that would either fail
> to build in configurations without D128 support or, if D128 becomes a
> runtime option, silently permit tearing on systems without the required
> hardware support.
>
> Instead, standardize P4D accesses on the existing page-table helpers.
> These can be overridden on arm64 to provide 128-bit single-copy
> atomicity when required.
>
> For now override p4dp_get() which is same as the generic memory default
> to avoid build dependency problem for callers in header <asm/pgtable.h>.
>
> No functional change intended.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kasan-dev@googlegroups.com
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
> Changes in V3
>
> - Added platform override for p4dp_get()
> - Replaced READ_ONCE() in pud_offset_phys() and pud_offset()
>
> arch/arm64/include/asm/pgtable.h | 10 ++++++++--
> arch/arm64/mm/fault.c | 2 +-
> arch/arm64/mm/fixmap.c | 2 +-
> arch/arm64/mm/hugetlbpage.c | 2 +-
> arch/arm64/mm/kasan_init.c | 4 ++--
> arch/arm64/mm/mmu.c | 12 ++++++------
> arch/arm64/mm/pageattr.c | 2 +-
> arch/arm64/mm/trans_pgd.c | 4 ++--
> 8 files changed, 22 insertions(+), 16 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index b46930f844a2..f235f68a7518 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -96,6 +96,12 @@ static inline pud_t pudp_get(pud_t *pudp)
> return READ_ONCE(*pudp);
> }
>
> +#define p4dp_get p4dp_get
> +static inline p4d_t p4dp_get(p4d_t *p4dp)
> +{
> + return READ_ONCE(*p4dp);
> +}
> +
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>
> @@ -976,7 +982,7 @@ static inline phys_addr_t pud_offset_phys(p4d_t *p4dp, unsigned long addr)
> {
> VM_WARN_ON_ONCE(!pgtable_l4_enabled());
>
> - return p4d_page_paddr(READ_ONCE(*p4dp)) + pud_index(addr) * sizeof(pud_t);
> + return p4d_page_paddr(p4dp_get(p4dp)) + pud_index(addr) * sizeof(pud_t);
> }
>
> static inline
> @@ -990,7 +996,7 @@ pud_t *pud_offset_lockless(p4d_t *p4dp, p4d_t p4d, unsigned long addr)
>
> static inline pud_t *pud_offset(p4d_t *p4dp, unsigned long addr)
> {
> - return pud_offset_lockless(p4dp, READ_ONCE(*p4dp), addr);
> + return pud_offset_lockless(p4dp, p4dp_get(p4dp), addr);
> }
> #define pud_offset pud_offset
>
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 435e2e14c070..a6afd8929a10 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -174,7 +174,7 @@ static void show_pte(unsigned long addr)
> break;
>
> p4dp = p4d_offset_lockless(pgdp, pgd, addr);
> - p4d = READ_ONCE(*p4dp);
> + p4d = p4dp_get(p4dp);
> ptval_to_str(pxd_str, p4d_val(p4d));
> pr_cont(", p4d=%s", pxd_str);
> if (p4d_none(p4d) || p4d_bad(p4d))
> diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
> index d9a870836faf..2a0fe0b0f771 100644
> --- a/arch/arm64/mm/fixmap.c
> +++ b/arch/arm64/mm/fixmap.c
> @@ -74,7 +74,7 @@ static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
> static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr,
> unsigned long end)
> {
> - p4d_t p4d = READ_ONCE(*p4dp);
> + p4d_t p4d = p4dp_get(p4dp);
> pud_t *pudp;
>
> if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) &&
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index c9ad5e75b073..5771bf49e1fe 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -288,7 +288,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
> return NULL;
>
> p4dp = p4d_offset(pgdp, addr);
> - if (!p4d_present(READ_ONCE(*p4dp)))
> + if (!p4d_present(p4dp_get(p4dp)))
> return NULL;
>
> pudp = pud_offset(p4dp, addr);
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index aad29bcc7622..4dd8c1186471 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -89,7 +89,7 @@ static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node,
> static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node,
> bool early)
> {
> - if (p4d_none(READ_ONCE(*p4dp))) {
> + if (p4d_none(p4dp_get(p4dp))) {
> phys_addr_t pud_phys = early ?
> __pa_symbol(kasan_early_shadow_pud)
> : kasan_alloc_zeroed_page(node);
> @@ -162,7 +162,7 @@ static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr,
> do {
> next = p4d_addr_end(addr, end);
> kasan_pud_populate(p4dp, addr, next, node, early);
> - } while (p4dp++, addr = next, addr != end && p4d_none(READ_ONCE(*p4dp)));
> + } while (p4dp++, addr = next, addr != end && p4d_none(p4dp_get(p4dp)));
> }
>
> static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 22efaee79293..83709d987e7c 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -367,7 +367,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
> {
> int ret = 0;
> unsigned long next;
> - p4d_t p4d = READ_ONCE(*p4dp);
> + p4d_t p4d = p4dp_get(p4dp);
> pud_t *pudp;
>
> if (p4d_none(p4d)) {
> @@ -457,7 +457,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
> }
>
> do {
> - p4d_t old_p4d = READ_ONCE(*p4dp);
> + p4d_t old_p4d = p4dp_get(p4dp);
>
> next = p4d_addr_end(addr, end);
>
> @@ -467,7 +467,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
> goto out;
>
> VM_WARN_ON_ONCE(p4d_val(old_p4d) != 0 &&
> - p4d_val(old_p4d) != READ_ONCE(p4d_val(*p4dp)));
> + p4d_val(old_p4d) != (p4d_val(p4dp_get(p4dp))));
>
> phys += next - addr;
> } while (p4dp++, addr = next, addr != end);
> @@ -1622,7 +1622,7 @@ static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr,
> do {
> next = p4d_addr_end(addr, end);
> p4dp = p4d_offset(pgdp, addr);
> - p4d = READ_ONCE(*p4dp);
> + p4d = p4dp_get(p4dp);
> if (p4d_none(p4d))
> continue;
>
> @@ -1788,7 +1788,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr,
> do {
> next = p4d_addr_end(addr, end);
> p4dp = p4d_offset(pgdp, addr);
> - p4d = READ_ONCE(*p4dp);
> + p4d = p4dp_get(p4dp);
> if (p4d_none(p4d))
> continue;
>
> @@ -1809,7 +1809,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr,
> */
> p4dp = p4d_offset(pgdp, 0UL);
> for (i = 0; i < PTRS_PER_P4D; i++) {
> - if (!p4d_none(READ_ONCE(p4dp[i])))
> + if (!p4d_none(p4dp_get(p4dp + i)))
> return;
> }
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 07b2fa4de57f..826856ef64a8 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -403,7 +403,7 @@ bool kernel_page_present(struct page *page)
> return false;
>
> p4dp = p4d_offset(pgdp, addr);
> - if (p4d_none(READ_ONCE(*p4dp)))
> + if (p4d_none(p4dp_get(p4dp)))
> return false;
>
> pudp = pud_offset(p4dp, addr);
> diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
> index d119119455f1..7afe2beca4ba 100644
> --- a/arch/arm64/mm/trans_pgd.c
> +++ b/arch/arm64/mm/trans_pgd.c
> @@ -99,7 +99,7 @@ static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp,
> unsigned long next;
> unsigned long addr = start;
>
> - if (p4d_none(READ_ONCE(*dst_p4dp))) {
> + if (p4d_none(p4dp_get(dst_p4dp))) {
> dst_pudp = trans_alloc(info);
> if (!dst_pudp)
> return -ENOMEM;
> @@ -145,7 +145,7 @@ static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp,
> src_p4dp = p4d_offset(src_pgdp, start);
> do {
> next = p4d_addr_end(addr, end);
> - if (p4d_none(READ_ONCE(*src_p4dp)))
> + if (p4d_none(p4dp_get(src_p4dp)))
> continue;
> if (copy_pud(info, dst_p4dp, src_p4dp, addr, next))
> return -ENOMEM;
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH V3 4/4] arm64/mm: Use pgdp_get() for PGD accesses
2026-09-24 6:22 [PATCH V3 0/4] arm64/mm: Convert pgtable READ_ONCE() as pxdp_get() Anshuman Khandual
` (2 preceding siblings ...)
2026-09-24 6:22 ` [PATCH V3 3/4] arm64/mm: Use p4dp_get() for P4D accesses Anshuman Khandual
@ 2026-09-24 6:22 ` Anshuman Khandual
2026-09-24 12:10 ` Ryan Roberts
3 siblings, 1 reply; 9+ messages in thread
From: Anshuman Khandual @ 2026-09-24 6:22 UTC (permalink / raw)
To: linux-arm-kernel
Cc: Anshuman Khandual, Catalin Marinas, Will Deacon, Ryan Roberts,
Mark Rutland, Lorenzo Stoakes, Andrew Morton, David Hildenbrand,
Mike Rapoport, Linu Cherian, linux-kernel, linux-mm, kasan-dev
Replace READ_ONCE() with pgdp_get() for PGD accesses in preparation for
supporting both D64 and D128 translation table formats.
READ_ONCE() cannot currently be used for 128-bit page table entries on
arm64 because it does not provide the required 128-bit single-copy
atomicity, causing builds to fail for accesses wider than 64 bits.
Although LDP/STP provide the required atomicity when FEAT_LSE is
available (as required by FEAT_D128), extending READ_ONCE() to support
128-bit accesses is undesirable. READ_ONCE() is a general-purpose API,
so doing so could encourage other 128-bit users that would either fail
to build in configurations without D128 support or, if D128 becomes a
runtime option, silently permit tearing on systems without the required
hardware support.
Instead, standardize PGD accesses on the existing page-table helpers.
These can be overridden on arm64 to provide 128-bit single-copy
atomicity when required.
For now override pgdp_get() which is same as the generic memory default
to avoid build dependency problem for callers in header <asm/pgtable.h>.
No functional change intended.
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: kasan-dev@googlegroups.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V3
- Added platform override for pgdp_get()
- Replaced READ_ONCE() in p4d_offset_phys() and p4d_offset()
arch/arm64/include/asm/pgtable.h | 10 ++++++++--
arch/arm64/mm/fault.c | 2 +-
arch/arm64/mm/hugetlbpage.c | 2 +-
arch/arm64/mm/kasan_init.c | 6 +++---
arch/arm64/mm/mmu.c | 6 +++---
arch/arm64/mm/pageattr.c | 2 +-
arch/arm64/mm/trans_pgd.c | 4 ++--
7 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index f235f68a7518..05d273f276b8 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -102,6 +102,12 @@ static inline p4d_t p4dp_get(p4d_t *p4dp)
return READ_ONCE(*p4dp);
}
+#define pgdp_get pgdp_get
+static inline pgd_t pgdp_get(pgd_t *pgdp)
+{
+ return READ_ONCE(*pgdp);
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
@@ -1102,7 +1108,7 @@ static inline phys_addr_t p4d_offset_phys(pgd_t *pgdp, unsigned long addr)
{
VM_WARN_ON_ONCE(!pgtable_l5_enabled());
- return pgd_page_paddr(READ_ONCE(*pgdp)) + p4d_index(addr) * sizeof(p4d_t);
+ return pgd_page_paddr(pgdp_get(pgdp)) + p4d_index(addr) * sizeof(p4d_t);
}
static inline
@@ -1116,7 +1122,7 @@ p4d_t *p4d_offset_lockless(pgd_t *pgdp, pgd_t pgd, unsigned long addr)
static inline p4d_t *p4d_offset(pgd_t *pgdp, unsigned long addr)
{
- return p4d_offset_lockless(pgdp, READ_ONCE(*pgdp), addr);
+ return p4d_offset_lockless(pgdp, pgdp_get(pgdp), addr);
}
static inline p4d_t *p4d_set_fixmap(unsigned long addr)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index a6afd8929a10..43f25418275a 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -160,7 +160,7 @@ static void show_pte(unsigned long addr)
guard(irqsave)();
pgdp = pgd_offset(mm, addr);
- pgd = READ_ONCE(*pgdp);
+ pgd = pgdp_get(pgdp);
ptval_to_str(pxd_str, pgd_val(pgd));
pr_alert("[%016lx] pgd=%s", addr, pxd_str);
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 5771bf49e1fe..e05e5b41ae50 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -284,7 +284,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
pmd_t *pmdp, pmd;
pgdp = pgd_offset(mm, addr);
- if (!pgd_present(READ_ONCE(*pgdp)))
+ if (!pgd_present(pgdp_get(pgdp)))
return NULL;
p4dp = p4d_offset(pgdp, addr);
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 4dd8c1186471..f61f5bc09467 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -102,7 +102,7 @@ static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node,
static p4d_t *__init kasan_p4d_offset(pgd_t *pgdp, unsigned long addr, int node,
bool early)
{
- if (pgd_none(READ_ONCE(*pgdp))) {
+ if (pgd_none(pgdp_get(pgdp))) {
phys_addr_t p4d_phys = early ?
__pa_symbol(kasan_early_shadow_p4d)
: kasan_alloc_zeroed_page(node);
@@ -256,7 +256,7 @@ static int __init root_level_idx(u64 addr)
static void __init clone_next_level(u64 addr, pgd_t *tmp_pg_dir, pud_t *pud)
{
int idx = root_level_idx(addr);
- pgd_t pgd = READ_ONCE(swapper_pg_dir[idx]);
+ pgd_t pgd = pgdp_get(swapper_pg_dir + idx);
pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
memcpy(pud, pudp, PAGE_SIZE);
@@ -280,7 +280,7 @@ static int __init next_level_idx(u64 addr)
*/
static void __init clear_next_level(int pgd_idx, int start, int end)
{
- pgd_t pgd = READ_ONCE(swapper_pg_dir[pgd_idx]);
+ pgd_t pgd = pgdp_get(swapper_pg_dir + pgd_idx);
pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
memset(&pudp[start], 0, (end - start) * sizeof(pud_t));
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 83709d987e7c..76d8d320aeed 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -434,7 +434,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
{
int ret;
unsigned long next;
- pgd_t pgd = READ_ONCE(*pgdp);
+ pgd_t pgd = pgdp_get(pgdp);
p4d_t *p4dp;
if (pgd_none(pgd)) {
@@ -1649,7 +1649,7 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end,
do {
next = pgd_addr_end(addr, end);
pgdp = pgd_offset_k(addr);
- pgd = READ_ONCE(*pgdp);
+ pgd = pgdp_get(pgdp);
if (pgd_none(pgd))
continue;
@@ -1827,7 +1827,7 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
do {
next = pgd_addr_end(addr, end);
pgdp = pgd_offset_k(addr);
- pgd = READ_ONCE(*pgdp);
+ pgd = pgdp_get(pgdp);
if (pgd_none(pgd))
continue;
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 826856ef64a8..dfa1356daac2 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -399,7 +399,7 @@ bool kernel_page_present(struct page *page)
unsigned long addr = (unsigned long)page_address(page);
pgdp = pgd_offset_k(addr);
- if (pgd_none(READ_ONCE(*pgdp)))
+ if (pgd_none(pgdp_get(pgdp)))
return false;
p4dp = p4d_offset(pgdp, addr);
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index 7afe2beca4ba..06470d690f9f 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c
@@ -134,7 +134,7 @@ static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp,
unsigned long next;
unsigned long addr = start;
- if (pgd_none(READ_ONCE(*dst_pgdp))) {
+ if (pgd_none(pgdp_get(dst_pgdp))) {
dst_p4dp = trans_alloc(info);
if (!dst_p4dp)
return -ENOMEM;
@@ -164,7 +164,7 @@ static int copy_page_tables(struct trans_pgd_info *info, pgd_t *dst_pgdp,
dst_pgdp = pgd_offset_pgd(dst_pgdp, start);
do {
next = pgd_addr_end(addr, end);
- if (pgd_none(READ_ONCE(*src_pgdp)))
+ if (pgd_none(pgdp_get(src_pgdp)))
continue;
if (copy_p4d(info, dst_pgdp, src_pgdp, addr, next))
return -ENOMEM;
--
2.43.0
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH V3 4/4] arm64/mm: Use pgdp_get() for PGD accesses
2026-09-24 6:22 ` [PATCH V3 4/4] arm64/mm: Use pgdp_get() for PGD accesses Anshuman Khandual
@ 2026-09-24 12:10 ` Ryan Roberts
0 siblings, 0 replies; 9+ messages in thread
From: Ryan Roberts @ 2026-09-24 12:10 UTC (permalink / raw)
To: Anshuman Khandual, linux-arm-kernel
Cc: Catalin Marinas, Will Deacon, Mark Rutland, Lorenzo Stoakes,
Andrew Morton, David Hildenbrand, Mike Rapoport, Linu Cherian,
linux-kernel, linux-mm, kasan-dev
On 24/09/2026 07:22, Anshuman Khandual wrote:
> Replace READ_ONCE() with pgdp_get() for PGD accesses in preparation for
> supporting both D64 and D128 translation table formats.
>
> READ_ONCE() cannot currently be used for 128-bit page table entries on
> arm64 because it does not provide the required 128-bit single-copy
> atomicity, causing builds to fail for accesses wider than 64 bits.
>
> Although LDP/STP provide the required atomicity when FEAT_LSE is
> available (as required by FEAT_D128), extending READ_ONCE() to support
> 128-bit accesses is undesirable. READ_ONCE() is a general-purpose API,
> so doing so could encourage other 128-bit users that would either fail
> to build in configurations without D128 support or, if D128 becomes a
> runtime option, silently permit tearing on systems without the required
> hardware support.
>
> Instead, standardize PGD accesses on the existing page-table helpers.
> These can be overridden on arm64 to provide 128-bit single-copy
> atomicity when required.
>
> For now override pgdp_get() which is same as the generic memory default
> to avoid build dependency problem for callers in header <asm/pgtable.h>.
>
> No functional change intended.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kasan-dev@googlegroups.com
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
> Changes in V3
>
> - Added platform override for pgdp_get()
> - Replaced READ_ONCE() in p4d_offset_phys() and p4d_offset()
>
> arch/arm64/include/asm/pgtable.h | 10 ++++++++--
> arch/arm64/mm/fault.c | 2 +-
> arch/arm64/mm/hugetlbpage.c | 2 +-
> arch/arm64/mm/kasan_init.c | 6 +++---
> arch/arm64/mm/mmu.c | 6 +++---
> arch/arm64/mm/pageattr.c | 2 +-
> arch/arm64/mm/trans_pgd.c | 4 ++--
> 7 files changed, 19 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index f235f68a7518..05d273f276b8 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -102,6 +102,12 @@ static inline p4d_t p4dp_get(p4d_t *p4dp)
> return READ_ONCE(*p4dp);
> }
>
> +#define pgdp_get pgdp_get
> +static inline pgd_t pgdp_get(pgd_t *pgdp)
> +{
> + return READ_ONCE(*pgdp);
> +}
> +
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
>
> @@ -1102,7 +1108,7 @@ static inline phys_addr_t p4d_offset_phys(pgd_t *pgdp, unsigned long addr)
> {
> VM_WARN_ON_ONCE(!pgtable_l5_enabled());
>
> - return pgd_page_paddr(READ_ONCE(*pgdp)) + p4d_index(addr) * sizeof(p4d_t);
> + return pgd_page_paddr(pgdp_get(pgdp)) + p4d_index(addr) * sizeof(p4d_t);
> }
>
> static inline
> @@ -1116,7 +1122,7 @@ p4d_t *p4d_offset_lockless(pgd_t *pgdp, pgd_t pgd, unsigned long addr)
>
> static inline p4d_t *p4d_offset(pgd_t *pgdp, unsigned long addr)
> {
> - return p4d_offset_lockless(pgdp, READ_ONCE(*pgdp), addr);
> + return p4d_offset_lockless(pgdp, pgdp_get(pgdp), addr);
> }
>
> static inline p4d_t *p4d_set_fixmap(unsigned long addr)
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index a6afd8929a10..43f25418275a 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -160,7 +160,7 @@ static void show_pte(unsigned long addr)
> guard(irqsave)();
>
> pgdp = pgd_offset(mm, addr);
> - pgd = READ_ONCE(*pgdp);
> + pgd = pgdp_get(pgdp);
> ptval_to_str(pxd_str, pgd_val(pgd));
> pr_alert("[%016lx] pgd=%s", addr, pxd_str);
>
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 5771bf49e1fe..e05e5b41ae50 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -284,7 +284,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm,
> pmd_t *pmdp, pmd;
>
> pgdp = pgd_offset(mm, addr);
> - if (!pgd_present(READ_ONCE(*pgdp)))
> + if (!pgd_present(pgdp_get(pgdp)))
> return NULL;
>
> p4dp = p4d_offset(pgdp, addr);
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 4dd8c1186471..f61f5bc09467 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -102,7 +102,7 @@ static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node,
> static p4d_t *__init kasan_p4d_offset(pgd_t *pgdp, unsigned long addr, int node,
> bool early)
> {
> - if (pgd_none(READ_ONCE(*pgdp))) {
> + if (pgd_none(pgdp_get(pgdp))) {
> phys_addr_t p4d_phys = early ?
> __pa_symbol(kasan_early_shadow_p4d)
> : kasan_alloc_zeroed_page(node);
> @@ -256,7 +256,7 @@ static int __init root_level_idx(u64 addr)
> static void __init clone_next_level(u64 addr, pgd_t *tmp_pg_dir, pud_t *pud)
> {
> int idx = root_level_idx(addr);
> - pgd_t pgd = READ_ONCE(swapper_pg_dir[idx]);
> + pgd_t pgd = pgdp_get(swapper_pg_dir + idx);
> pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
>
> memcpy(pud, pudp, PAGE_SIZE);
> @@ -280,7 +280,7 @@ static int __init next_level_idx(u64 addr)
> */
> static void __init clear_next_level(int pgd_idx, int start, int end)
> {
> - pgd_t pgd = READ_ONCE(swapper_pg_dir[pgd_idx]);
> + pgd_t pgd = pgdp_get(swapper_pg_dir + pgd_idx);
> pud_t *pudp = (pud_t *)__phys_to_kimg(__pgd_to_phys(pgd));
>
> memset(&pudp[start], 0, (end - start) * sizeof(pud_t));
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 83709d987e7c..76d8d320aeed 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -434,7 +434,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end,
> {
> int ret;
> unsigned long next;
> - pgd_t pgd = READ_ONCE(*pgdp);
> + pgd_t pgd = pgdp_get(pgdp);
> p4d_t *p4dp;
>
> if (pgd_none(pgd)) {
> @@ -1649,7 +1649,7 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end,
> do {
> next = pgd_addr_end(addr, end);
> pgdp = pgd_offset_k(addr);
> - pgd = READ_ONCE(*pgdp);
> + pgd = pgdp_get(pgdp);
> if (pgd_none(pgd))
> continue;
>
> @@ -1827,7 +1827,7 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
> do {
> next = pgd_addr_end(addr, end);
> pgdp = pgd_offset_k(addr);
> - pgd = READ_ONCE(*pgdp);
> + pgd = pgdp_get(pgdp);
> if (pgd_none(pgd))
> continue;
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 826856ef64a8..dfa1356daac2 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -399,7 +399,7 @@ bool kernel_page_present(struct page *page)
> unsigned long addr = (unsigned long)page_address(page);
>
> pgdp = pgd_offset_k(addr);
> - if (pgd_none(READ_ONCE(*pgdp)))
> + if (pgd_none(pgdp_get(pgdp)))
> return false;
>
> p4dp = p4d_offset(pgdp, addr);
> diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
> index 7afe2beca4ba..06470d690f9f 100644
> --- a/arch/arm64/mm/trans_pgd.c
> +++ b/arch/arm64/mm/trans_pgd.c
> @@ -134,7 +134,7 @@ static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp,
> unsigned long next;
> unsigned long addr = start;
>
> - if (pgd_none(READ_ONCE(*dst_pgdp))) {
> + if (pgd_none(pgdp_get(dst_pgdp))) {
> dst_p4dp = trans_alloc(info);
> if (!dst_p4dp)
> return -ENOMEM;
> @@ -164,7 +164,7 @@ static int copy_page_tables(struct trans_pgd_info *info, pgd_t *dst_pgdp,
> dst_pgdp = pgd_offset_pgd(dst_pgdp, start);
> do {
> next = pgd_addr_end(addr, end);
> - if (pgd_none(READ_ONCE(*src_pgdp)))
> + if (pgd_none(pgdp_get(src_pgdp)))
> continue;
> if (copy_p4d(info, dst_pgdp, src_pgdp, addr, next))
> return -ENOMEM;
^ permalink raw reply [flat|nested] 9+ messages in thread