From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4546EC98305 for ; Tue, 22 Sep 2026 06:17:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=xLAWG+zZZwAZ8VbqEUmqIMJ4/VP13qJLKYc2nU29x0c=; b=B1XzyowsiTZMDapXBqzyp65Gob U66/cuLEjD9QsGeIrOCxpgjZc0LpTES9zYb/h0r9W7cgQJm6d6K3eaEJYmqymxH/4dJ8yHQxxdT+F hcs8Sm9AgOetTdsDndhUbMAicWSe7s0MCqGhbcLtx+sX/in3gmWgQSljzc5WFH+k4H+bBPf9IRi4l /+6V7tyhstL7NAyvd52hxwNZJwwu8Kp9JwY6Te3nd9Va1AuFe7jkdgaF2LY2iGD67CvAfaxVUSJKC xJF/dw8yz6VfDS3T+vwMMs/zmCoFP94pkGQBl/rcFBiI+N2bh79phnaXLoVCjtacrxMXiaMZVjtbM prpnhIhw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8toN-00000004JwO-3iqy; Tue, 22 Sep 2026 06:17:03 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x8toK-00000004JuD-1NtL for linux-arm-kernel@lists.infradead.org; Tue, 22 Sep 2026 06:17:02 +0000 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 9F29C152B; Mon, 21 Sep 2026 23:16:55 -0700 (PDT) Received: from localhost (a085714.arm.com [10.164.19.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6F45F3F632; Mon, 21 Sep 2026 23:16:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790057819; bh=YPhwXo+wZb0LPzJLyEuEwvluXfQVUw7xmrdIkATrj74=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cg8BnpDI/5IKSPk/5ru5ySdweqI1LGvk1Pa2oXZsbp3x36QOPFvgMuaia0rW5PPLp dhvJ7I7EH2FSskGukOJLnUcHlRc6HS7ihY1PRZ+toTOH90AQVnzXd62YuoU6TOJP+A 12/IDLzudXUaqgX2a99CidvFZ2M8FlWRhdaFPevo= 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 4/4] arm64/mm: Use pgdp_get() for PGD accesses Date: Tue, 22 Sep 2026 11:46:38 +0530 Message-ID: <20260922061638.3967467-5-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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260921_231701_880940_BD8F86F4 X-CRM114-Status: GOOD ( 17.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. 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/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 ++-- 6 files changed, 11 insertions(+), 11 deletions(-) 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