From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5DF584028C3 for ; Thu, 24 Sep 2026 06:22:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790230960; cv=none; b=t7nlaq/LP9KDK1/iMXrYO0NXYGu1z7LoOrUEgTHGk9JxoYmdAS5Fv9NzvcMuFZL+4RIitXuU3TGGQnYAhd/Tacl6cTdu4A3SCekfqq5k/gSsh/QEdVg6Ig8xhQWq3LhzrOcufBqiWRe16dBWQ6p8bv5FwEQdLxAf8ZdSgA9+fio= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790230960; c=relaxed/simple; bh=MbarBIp95Pz3ZZkxqGhq8vWSNi6Qxjc6YojSk+L58R4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=oLeGEcnARtimTnXvfATfJLN3i8D3JBmuVbkY0UGkMjIwHXyAPgxW2buxjFWkz4K30ALYlw4PYpp+GB4NwhJRlUsixe4veORM4sCMUv8H6yXq3NdJebRtYT3KCqZ3t9yxG26iQ1/F+FEKrgsqluBTTI2vz+UJVV6ccuYuSqxRDf4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=Cm95oBd8; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="Cm95oBd8" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 484271682; Wed, 23 Sep 2026 23:22:34 -0700 (PDT) Received: from localhost (a085714.arm.com [10.164.19.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0F3B23F86C; Wed, 23 Sep 2026 23:22:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790230957; bh=MbarBIp95Pz3ZZkxqGhq8vWSNi6Qxjc6YojSk+L58R4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Cm95oBd8XRa6BEsVHeaJqsurIo0tIR1i4OeiLxj8Cdc7CcvCD46G8IgbYQsSmTzOc 3FcRm11y545CyEPF3NAyOUvtK4BtG2vOmoL2R3uMNR8dc9tNGNb5jGl/6JBpuZ+J8N qQf6LBycrt1yMY3dsWI4qtF0DGNZtG52JoaPJPQc= 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 4/4] arm64/mm: Use pgdp_get() for PGD accesses Date: Thu, 24 Sep 2026 11:52:14 +0530 Message-ID: <20260924062214.1635078-5-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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 . 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 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