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 11606C98310 for ; Thu, 24 Sep 2026 06:22:59 +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=kxyIbo/u3CdsE7qDsWfTtiTeOUnmJko1bwoqVR/WV28=; b=qLV792vLnJXfHwvDhcwbeaQNz7 vxKdomf0bvIiury6xSp0hqu8LHzm1EsjYKx9V19AVU4NkoouAxfpP0W9Qle+yu5ChhgyrSD6yZpoA R3UlALsjT/AYnRgkaKQk15dkWhJwbeJlEPS3hsBef2rYeTOjkIgjGTJX7id6xIpO1Rx/5OsmzAtzs IlQWIG/r9RDoIRpo5K95rp2ffN5uAOFdos4a1f5AH2oBrZjEWB+Nb/+JJRE1NjEx6wHJ5BKyt5J2I Mg+TcE8hN0TNqGuWOyNh3U64cUrhegi1luIlaQvJw9A/GZLM/hsJ4sks4EFvcZODAijjoBRjiWDgG EgmJ0FvQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x9cr6-0000000A993-0LGu; Thu, 24 Sep 2026 06:22:52 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x9cqx-0000000A960-1oBU for linux-arm-kernel@bombadil.infradead.org; Thu, 24 Sep 2026 06:22:47 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:MIME-Version :References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description; bh=kxyIbo/u3CdsE7qDsWfTtiTeOUnmJko1bwoqVR/WV28=; b=PdI0njl9TXMwvIS97PId9aiMH/ yyBbdX7dgYSyjkOYgwRXAfvkNOSJQG8YOXO6ZwUbKXELLQWvtY5/ByDJrPAfA1TU1jDc1SAcR3dt5 3pi24a7e++I7d8PPHaPPEPDXr/QAaROyRRC5jFzaEPVP7hh/mHH08TRhN1C/fIlysxCwv6q4AFwRn pbDQaSw4qGFNpQwvVZ1UH+bgXjlwg0c5zce00+Nv3kCn8kO0tPeabfuHR76SdaaegRRC4YoXMmWGO YWy31o8bjuDZDCetjWo/DgB/uhirZ95a7s6JZGpbGewRbX4pf304IQeA9tABVhrysNIeXmNgcDh8Q TgvtvR2w==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.99.2 #2 (Red Hat Linux)) id 1x9cqr-0000000Fajm-3HZD for linux-arm-kernel@lists.infradead.org; Thu, 24 Sep 2026 06:22:42 +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 6F1641650; Wed, 23 Sep 2026 23:22:30 -0700 (PDT) Received: from localhost (a085714.arm.com [10.164.19.28]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 37B9F3F86C; Wed, 23 Sep 2026 23:22:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1790230953; bh=Izqyl3NqNDKyfXa9ucdwjbJWtozKpu+9KkF7o0jxLqU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OPa+4zC9f9wtpdd0jHUw79KM+PmDxqo33Qy51Nr+CSk2x54pJbO4UOQECBNk17oDq 47MeSSMtXam3UGJyZu6M9VB3iRorzwxWRsq7g8W5HqFQbtmH5CdE98QL3hJFujMxol IgHW3ux46V5woHgSfjyTUXHAUC4ccX0FKBiX3G6Q= 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 3/4] arm64/mm: Use p4dp_get() for P4D accesses Date: Thu, 24 Sep 2026 11:52:13 +0530 Message-ID: <20260924062214.1635078-4-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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260924_072240_163324_1215D04E X-CRM114-Status: GOOD ( 21.14 ) 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 p4dp_get() for P4D 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 P4D 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 p4dp_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 p4dp_get() - Replaced READ_ONCE() in pud_offset_phys() and pud_offset() arch/arm64/include/asm/pgtable.h | 10 ++++++++-- 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 | 12 ++++++------ arch/arm64/mm/pageattr.c | 2 +- arch/arm64/mm/trans_pgd.c | 4 ++-- 8 files changed, 22 insertions(+), 16 deletions(-) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index b46930f844a2..f235f68a7518 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -96,6 +96,12 @@ static inline pud_t pudp_get(pud_t *pudp) return READ_ONCE(*pudp); } +#define p4dp_get p4dp_get +static inline p4d_t p4dp_get(p4d_t *p4dp) +{ + return READ_ONCE(*p4dp); +} + #ifdef CONFIG_TRANSPARENT_HUGEPAGE #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE @@ -976,7 +982,7 @@ static inline phys_addr_t pud_offset_phys(p4d_t *p4dp, unsigned long addr) { VM_WARN_ON_ONCE(!pgtable_l4_enabled()); - return p4d_page_paddr(READ_ONCE(*p4dp)) + pud_index(addr) * sizeof(pud_t); + return p4d_page_paddr(p4dp_get(p4dp)) + pud_index(addr) * sizeof(pud_t); } static inline @@ -990,7 +996,7 @@ pud_t *pud_offset_lockless(p4d_t *p4dp, p4d_t p4d, unsigned long addr) static inline pud_t *pud_offset(p4d_t *p4dp, unsigned long addr) { - return pud_offset_lockless(p4dp, READ_ONCE(*p4dp), addr); + return pud_offset_lockless(p4dp, p4dp_get(p4dp), addr); } #define pud_offset pud_offset diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 435e2e14c070..a6afd8929a10 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -174,7 +174,7 @@ static void show_pte(unsigned long addr) break; p4dp = p4d_offset_lockless(pgdp, pgd, addr); - p4d = READ_ONCE(*p4dp); + p4d = p4dp_get(p4dp); ptval_to_str(pxd_str, p4d_val(p4d)); pr_cont(", p4d=%s", pxd_str); if (p4d_none(p4d) || p4d_bad(p4d)) diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c index d9a870836faf..2a0fe0b0f771 100644 --- a/arch/arm64/mm/fixmap.c +++ b/arch/arm64/mm/fixmap.c @@ -74,7 +74,7 @@ static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr, static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end) { - p4d_t p4d = READ_ONCE(*p4dp); + p4d_t p4d = p4dp_get(p4dp); pud_t *pudp; if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) && diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index c9ad5e75b073..5771bf49e1fe 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -288,7 +288,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, return NULL; p4dp = p4d_offset(pgdp, addr); - if (!p4d_present(READ_ONCE(*p4dp))) + if (!p4d_present(p4dp_get(p4dp))) return NULL; pudp = pud_offset(p4dp, addr); diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c index aad29bcc7622..4dd8c1186471 100644 --- a/arch/arm64/mm/kasan_init.c +++ b/arch/arm64/mm/kasan_init.c @@ -89,7 +89,7 @@ static pmd_t *__init kasan_pmd_offset(pud_t *pudp, unsigned long addr, int node, static pud_t *__init kasan_pud_offset(p4d_t *p4dp, unsigned long addr, int node, bool early) { - if (p4d_none(READ_ONCE(*p4dp))) { + if (p4d_none(p4dp_get(p4dp))) { phys_addr_t pud_phys = early ? __pa_symbol(kasan_early_shadow_pud) : kasan_alloc_zeroed_page(node); @@ -162,7 +162,7 @@ static void __init kasan_p4d_populate(pgd_t *pgdp, unsigned long addr, do { next = p4d_addr_end(addr, end); kasan_pud_populate(p4dp, addr, next, node, early); - } while (p4dp++, addr = next, addr != end && p4d_none(READ_ONCE(*p4dp))); + } while (p4dp++, addr = next, addr != end && p4d_none(p4dp_get(p4dp))); } static void __init kasan_pgd_populate(unsigned long addr, unsigned long end, diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 22efaee79293..83709d987e7c 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -367,7 +367,7 @@ static int alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, { int ret = 0; unsigned long next; - p4d_t p4d = READ_ONCE(*p4dp); + p4d_t p4d = p4dp_get(p4dp); pud_t *pudp; if (p4d_none(p4d)) { @@ -457,7 +457,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end, } do { - p4d_t old_p4d = READ_ONCE(*p4dp); + p4d_t old_p4d = p4dp_get(p4dp); next = p4d_addr_end(addr, end); @@ -467,7 +467,7 @@ static int alloc_init_p4d(pgd_t *pgdp, unsigned long addr, unsigned long end, goto out; VM_WARN_ON_ONCE(p4d_val(old_p4d) != 0 && - p4d_val(old_p4d) != READ_ONCE(p4d_val(*p4dp))); + p4d_val(old_p4d) != (p4d_val(p4dp_get(p4dp)))); phys += next - addr; } while (p4dp++, addr = next, addr != end); @@ -1622,7 +1622,7 @@ static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr, do { next = p4d_addr_end(addr, end); p4dp = p4d_offset(pgdp, addr); - p4d = READ_ONCE(*p4dp); + p4d = p4dp_get(p4dp); if (p4d_none(p4d)) continue; @@ -1788,7 +1788,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr, do { next = p4d_addr_end(addr, end); p4dp = p4d_offset(pgdp, addr); - p4d = READ_ONCE(*p4dp); + p4d = p4dp_get(p4dp); if (p4d_none(p4d)) continue; @@ -1809,7 +1809,7 @@ static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr, */ p4dp = p4d_offset(pgdp, 0UL); for (i = 0; i < PTRS_PER_P4D; i++) { - if (!p4d_none(READ_ONCE(p4dp[i]))) + if (!p4d_none(p4dp_get(p4dp + i))) return; } diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 07b2fa4de57f..826856ef64a8 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -403,7 +403,7 @@ bool kernel_page_present(struct page *page) return false; p4dp = p4d_offset(pgdp, addr); - if (p4d_none(READ_ONCE(*p4dp))) + if (p4d_none(p4dp_get(p4dp))) return false; pudp = pud_offset(p4dp, addr); diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c index d119119455f1..7afe2beca4ba 100644 --- a/arch/arm64/mm/trans_pgd.c +++ b/arch/arm64/mm/trans_pgd.c @@ -99,7 +99,7 @@ static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp, unsigned long next; unsigned long addr = start; - if (p4d_none(READ_ONCE(*dst_p4dp))) { + if (p4d_none(p4dp_get(dst_p4dp))) { dst_pudp = trans_alloc(info); if (!dst_pudp) return -ENOMEM; @@ -145,7 +145,7 @@ static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp, src_p4dp = p4d_offset(src_pgdp, start); do { next = p4d_addr_end(addr, end); - if (p4d_none(READ_ONCE(*src_p4dp))) + if (p4d_none(p4dp_get(src_p4dp))) continue; if (copy_pud(info, dst_p4dp, src_p4dp, addr, next)) return -ENOMEM; -- 2.43.0