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h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eee0xbA8SYI+UnqHhB96wS8cBEoHBPgeBK4s30BWor/TVQIPRj8yB9qVvMkp3QXdC RCjAR5/PcuDAfJ9+ttTkkgPa/9ACBk2zS97xYTRDe2RQ7Z8f1e8LR+RHqLlWRlda2M kG1zdIiVDWxaDDw4kCyByys9lKNrVCJf0BZ1BMJ4= From: Anshuman Khandual To: linux-arm-kernel@lists.infradead.org Cc: Anshuman Khandual , Catalin Marinas , Will Deacon , Ryan Roberts , Mark Rutland , Lorenzo Stoakes , Andrew Morton , David Hildenbrand , Mike Rapoport , Linu Cherian , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com Subject: [PATCH V3 1/4] arm64/mm: Use pmdp_get() for PMD accesses Date: Thu, 24 Sep 2026 11:52:11 +0530 Message-ID: <20260924062214.1635078-2-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260924062214.1635078-1-anshuman.khandual@arm.com> References: <20260924062214.1635078-1-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 5ctc3nkfgyyxq5n6dr7h66m1mqfynqws X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 58D1480007 X-HE-Tag: 1790230947-809536 X-HE-Meta: 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 exlGUcp0 1s0skic7jKVufdG3XGW7yEdDF/Y9n77RHSNDqUPPfUR2Exn+4zAT8U8DFS+Z9GBfTgk8FQMhAqSuIN79lDlCul33SsEZ11iprADkmFMAFcLObSTaeK+pX2tp/zswS5Y57bazMkVFsCS81BjQ4p6XvEWlE64fYaXKqOFfDxOLAhG7TMHLiYhYp2NJ0R47nwsC3aL6rMxijaOECcwhkov5RfqSxjBTmBEJAkolpoDQXiWYYlO25apKgJ5UJ1rxrKpl0g8eBDjKU3e5nOAU2tJPMYCk9/1L+IZ2H8KNz0PYG8KPNZLFQXB6n9+rTOFYjhA31Myyq8SBwhKS5CHaQ9KbjEZYbG6zXa2s+IBj0UAFtjppt8OYc+xpwjBqlsD3NWB4XqAxMJmsqemZAxA3b2DioT12f2rD4EESh+XdF5uDrHWwZpNF5cYzZ8vFkM2lkpSweOrD1OFjxm+v/oJNmD0c4vuyQk5YMeN3IzWASl93U4hgEhaU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 . No functional change intended. Cc: Catalin Marinas Cc: Will Deacon Cc: Ryan Roberts Cc: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: kasan-dev@googlegroups.com Signed-off-by: Anshuman Khandual --- 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