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h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZimIwZ5GXmjKnSTq+el2RiaDXGsmQviBAqWAjRnxJ9q788vA7UgWgY6+04Vlmqsjx GNUqPDTPVkXJx9fxvEYYZVnFyT6WCL8UOSq6eKNwJ8hgKciIH8N+m+/1cM3q9Wj3On LZu1MZXGRpUkmAaNqTnmVJDjwi2CjdWiIdYSA8fY= 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, Mark Rtland , linx-arm-kernel@lists.infradead.org, linx-kernel@vger.kernel.org, kasan-dev@googlegrops.com Subject: [PATCH V2 1/4] arm64/mm: Use pmdp_get() for PMD accesses Date: Tue, 22 Sep 2026 11:46:35 +0530 Message-ID: <20260922061638.3967467-2-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260922061638.3967467-1-anshuman.khandual@arm.com> References: <20260922061638.3967467-1-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: euq1ko8gb1xbq4g3ugddzq1qrspn3aib X-Rspamd-Queue-Id: BCB04A0004 X-Rspamd-Server: rspam07 X-HE-Tag: 1790057808-772384 X-HE-Meta: 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 Yc/N7bJq oJQlzU8udV7LIay9U95Cnji0iR2Gq5KWMr9EjHVSIrJF/6nxriwwsIzOP2TLCcL0B/D+FEgHx8axzjewyZSvaqjpzVl3ByL2ASCmmCO8DLkmqs8ndp8yJ5e2PKutCoqAzvc5E50oguG0psICx63RuYotM6/K0Qo2SBXaoXfmfqTvUOx5F4prGGAcggBAsgvMP7q1zA0FZTcvgZ8NryXxA0D0fZDrGajSB7ZYwg5cLx9mtRzsZY97I5OhpgeyVPUy+5HY+jtC43LWQR2eto5BykUIY06Dtp2D8ndiNAnBnR4eE9a5DFnurq1APkU2rjtY6krxKhd4uWSRiSRp+bUT+PqXof6vleDK2x7XzXc3ZQVxzlVF7Y30VKTHKj5Dhe94pK8Conr+OWYcZn+l6KtQVykM1Zu2Dp2mVPCV1cZ6DM/KcY8TSFMQsKGGHIHliLC/6iO7DIN6sly84RTLk5Vm2OoAf4RjW0fOcv/vwQQCXc4jSqfk= 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. No functional change intended. Cc: Catalin Marinas Cc: Will Deacon Cc: Ryan Roberts Cc: Mark Rtland Cc: linx-arm-kernel@lists.infradead.org Cc: linx-kernel@vger.kernel.org Cc: kasan-dev@googlegrops.com Reviewed-by: Ryan Roberts Signed-off-by: Anshuman Khandual --- arch/arm64/include/asm/pgtable.h | 3 ++- 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, 20 insertions(+), 19 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 763c5a411d64..b953ea0ba3ed 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -811,7 +811,8 @@ 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)) 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