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c=simple/simple; d=arm.com; s=foss; t=1790057811; bh=YY1OaMPb64xJn1b27visI3ZEml4aTTF4OARXpGvoiBs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KrSj76Tl2tA6GkRkFYOY4euoKjudnSXomBvK8dIRRdxQ/KkBQHRk9plGZDshFnNOy dCH8xiR1sBwE1P1qOb6AYtcp9WOdcy7jf35iblUwnpMW4lOQ4CJ1628Hq+GlIf2bnl uyr9KnU84Nr/g7Z/LQKSptCA5ti32TFEFiKr4CEo= 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 V2 2/4] arm64/mm: Use pudp_get() for PUD accesses Date: Tue, 22 Sep 2026 11:46:36 +0530 Message-ID: <20260922061638.3967467-3-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-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 8D475C0003 X-Stat-Signature: 851h1k3bzouutrpfjmg8j4ddkf8ie415 X-HE-Tag: 1790057812-932564 X-HE-Meta: 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 PwNVOKnt RlW0qb0AC4/Li5lGxGk9y1/2NYc9A+u2sh7keK6uYmv2fpzNGwl7MupphiZEfeqGt85LfAuYkmk7Q99QHgN+zpwmDqwyGXYpbYlBgNAH+Jv40+JA5/hF3CtOyJanjZ9xZIYhVXHXNFj2y3qjXF+q5ebQ32CkreJUe8ATe8NuhvBbO+0kkBD2QDe2mSdihJ4RwMwY5DohOjyjTF8M/wpfMQaAz6fFNouEeqA7fUCGlQnK8uFKleKnUPNLM8BOlM+RqTfdQVPHZMFhn5qGhdHa3qiLsV8W7sW4xhHI6EuqtZzXIyC6A1+RoNxHf7qp7mh7je7DA7m2ruU9IglDmLNTIZdfktUSzenCaG9uR4hGNjBuBTc6OVtxXkzBL3hQhzicUBUHa9B+1WjSXdOPTdUaMUBTuNMHuinI41NzRUNOzvjUR8HcOfJHAvHQIevHN9yzkaF0oghYw6kvbxmZ0ZEA4IZbwc2r+PVCoHCGxc8R7OiQn1fs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. 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 --- arch/arm64/include/asm/pgtable.h | 3 ++- 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, 21 insertions(+), 20 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index b953ea0ba3ed..ae41946c54f2 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -873,7 +873,8 @@ 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