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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2BF4C83013 for ; Wed, 2 Jul 2025 08:32:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 702606B00BF; Wed, 2 Jul 2025 04:32:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6B2916B00C0; Wed, 2 Jul 2025 04:32:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 57A7F6B00C1; Wed, 2 Jul 2025 04:32:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 40FBE6B00BF for ; Wed, 2 Jul 2025 04:32:42 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id D9DB016079F for ; Wed, 2 Jul 2025 08:32:41 +0000 (UTC) X-FDA: 83618658522.19.F9189E8 Received: from mail-wm1-f44.google.com (mail-wm1-f44.google.com [209.85.128.44]) by imf07.hostedemail.com (Postfix) with ESMTP id C850440004 for ; Wed, 2 Jul 2025 08:32:39 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=SHo25pBX; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf07.hostedemail.com: domain of jannh@google.com designates 209.85.128.44 as permitted sender) smtp.mailfrom=jannh@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1751445159; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding:in-reply-to: references:dkim-signature; bh=XvcsilU1sW9ZroJrInpDuRq5bTBfyCF/BMtQir5LxGI=; b=yfL/VYa2LJYby3jCXEbHjF5aWW5UyEUawAF3GTVqlOq5LYrhEj2EEgxzG2x3QJ2gXHAG1u TCA9+M6lAEHatoxf1G7O8/d4u8rlZ7L7RVp2kv+cGRHJCPM/ZWEh1/WVGFb6jrj7I+ntOG xyms/pw0cLKZorUcwc93iob/+ic37F4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1751445159; a=rsa-sha256; cv=none; b=h6XxXk1buds7K1Cs+jhIbfFCvRevwb2KAGHABhScCNA1scwbBFIpkTYokimMDxCNj+IST3 kWtrW87HKDvKmifoiGhGQwwzhIlVFLODwgYzb85+9Ra/xvAxbpp0WOV1SK+XLBOxoDNT5y yhkQTnfQF9B3DEPaKvI6PHXla5y7b58= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=SHo25pBX; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf07.hostedemail.com: domain of jannh@google.com designates 209.85.128.44 as permitted sender) smtp.mailfrom=jannh@google.com Received: by mail-wm1-f44.google.com with SMTP id 5b1f17b1804b1-45390dcca6dso94275e9.1 for ; Wed, 02 Jul 2025 01:32:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1751445158; x=1752049958; darn=kvack.org; h=cc:to:message-id:content-transfer-encoding:mime-version:subject :date:from:from:to:cc:subject:date:message-id:reply-to; bh=XvcsilU1sW9ZroJrInpDuRq5bTBfyCF/BMtQir5LxGI=; b=SHo25pBXpfBPUdjej6Zn1ADWN3tAWHqZsuBrp2En4rwLr/L8wN2QISTRfZlu0ps1CR c320fwxJzoJjW3XoSas0ukwBFqv9fiXRITReX0Mcqbaw459mXSAbnJL+XVIdPFGPexNO 3Exi2aZCZy65Ql3NEAArhBryrpnI5CdI8wb87BTouxvJ1HUdzheWrS7Dj/3li6+SJndQ lizJdC6x69T4ACAWXH0hMtV1qYhvQAUvyBznSQiRY52OhGdR96ApOHcJDWMxq7ft0oVE DdL+16I85uACaly9aqMbbUhz74ByliHvQ0j2CUIN5bNXAh176wJEM9sgtU4JOn8Yv1uL SQdQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751445158; x=1752049958; h=cc:to:message-id:content-transfer-encoding:mime-version:subject :date:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=XvcsilU1sW9ZroJrInpDuRq5bTBfyCF/BMtQir5LxGI=; b=NmtvAKt0RQaq7nLMMI694HY0Nx0ZWBvFHXzq/OhiycjfOK4vHSNS7Lrt4yKpv+agrQ 9+tCf3++rvIjGzbfu+OmKv3jWh7BRAJuLOaI/ckOKUS7moNNkpKUgFkIHrSNAAiTKVgB C5veeFDZgSZZNsFSjySFCkZsx5Wy/9FU8hF5kojd79ska6milg2hiMRgYTE/iH1YmSb3 lChMcB3CqKiHgEctdWVsGzqnZFook+ZpOA2i101B/3VT/guTrkNeL0FYFimAhw0EiQbD DGFgDzqnQnp41lq/GtPRK+a5HyuDHiHAOPErZ50cSawSbBBUXxQ9Ubro/CexAEqf4Ejj erLQ== X-Forwarded-Encrypted: i=1; AJvYcCWZeSsCYVQ+/P1vYp5/u+xALRs6zpXPE5GgctIv7wwcQlumMV2nwpeZcdbXqGiqkC15xdDq7Ag8kw==@kvack.org X-Gm-Message-State: AOJu0YzrnotbK3i0507qLoz7i9tEVki5XEycy/fSipf2oogGJ1MiGMJP 2xBPs/w+iBdvGlpeh+zBfdzoQMFXv+xXdinYUKZ+gyHOAO1vF0bBTD5ElMWCgVL1xw== X-Gm-Gg: ASbGncviObRil7KT9LiKLbPHV6HfisaT34HR3ZLZhicb2lcJel5DPxkGXibRZfTAphA rTql5jcTqzyv9Pzf5wkRo0wq7wypltj8xFbN5GP6/vSdW0vxzhd2V4xPiOQHL/7xCphwP4AKXpR wFkFBW1JW/KhCghzMCjoNb2uxdjf5udoY+rktcugjJArhD6bUeHosWo/00XUnTGlxlSpK++2izK ye7WBuMB3RMokEqAM1iiXI6/8N0FJT3oBHzHjyYd6oe9E7C+zTd0kzkmuYq58XbhgweOiEKZZFP RbV3sp5k3feYV6bHHWHr10A5tBK0kjuAWrshF9k0kazPiZ025w== X-Google-Smtp-Source: AGHT+IFpZv2X4ec+NbYvtOFfMUhTvi0IIqKMta9hdoetaYBvp/OQbbyq8JB7TaOnylqpXCpoJ83zzg== X-Received: by 2002:a05:600c:a301:b0:453:5ffb:e007 with SMTP id 5b1f17b1804b1-453e03a982cmr2406815e9.4.1751445157740; Wed, 02 Jul 2025 01:32:37 -0700 (PDT) Received: from localhost ([2a00:79e0:9d:4:a624:383a:b7f6:98b6]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-4538a3fe587sm194408345e9.19.2025.07.02.01.32.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Jul 2025 01:32:37 -0700 (PDT) From: Jann Horn Date: Wed, 02 Jul 2025 10:32:04 +0200 Subject: [PATCH v2] x86/mm: Disable hugetlb page table sharing on 32-bit MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250702-x86-2level-hugetlb-v2-1-1a98096edf92@google.com> X-B4-Tracking: v=1; b=H4sIAIPuZGgC/32NQQ6DIBBFr2Jm3WkAg5queg/josIIJFQasMTGc PdSD9Dle8l//4BE0VGCW3NApOySC2sFcWlA2cdqCJ2uDIIJybqW4T50KDxl8mjfhjY/48z1sNA spFQEdfiKtLj9jI5TZevSFuLn/Mj8Z//mMkeOrO+Vlq0eavVuQjCerio8YSqlfAGMxjZptQAAA A== X-Change-ID: 20250630-x86-2level-hugetlb-b1d8feb255ce To: Dave Hansen , Andy Lutomirski , Peter Zijlstra Cc: Muchun Song , Oscar Salvador , Vitaly Chikunov , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dave Hansen , stable@vger.kernel.org, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1751445128; l=2325; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=eAWfGBOp2OE5o/uIStw/ne4ImpbU6xw1RGKMdwD5PrM=; b=3IjgsDhfn/5nRf4zEn2iPWeV2Su1iX72bqKFpVCmdzkQTIJkAmz8QikSuctlSlKeSLatqT9Nr pRjGbWN0vROA/pzHLwqxQRbqBtzR/FFfjEDRD+fhdunfjKxp7ptnLTV X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= X-Stat-Signature: yizkxryqakcitw6e3ou3y8huuw4xxanb X-Rspamd-Queue-Id: C850440004 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1751445159-643072 X-HE-Meta: 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 Ol/ccgmc ShCG5Pu652Sb5HxnQQX2mN3SojlkEMZYIaAfDRSJIc3QDWRabn+mHg8DLkkifrhE9CQ+Y9FUHQzJl73MNomTQju35pQFzKZSW1UmeSyHLS967rrQS3yDTP0ZzfPPtTbSijdYp1UXyWEHJ1Lb9QTEa5fbeaV5LX2QSebKLMxyYp9Zn3OIX+ZvkWq1DNzHDF/IUNZ4ly9hC2j98HqNJ15TQ6TSquqCuMWHBA1G2r0EQ/o59mAc0yDxRNtikzM3l5+u7ztOsNTjwRMtd1w8rzwosjjZTWQBNGAdYjU5q0XrZREY7pVWjWS+wD0kzkC7KAvW6879Ouqbxmo1lFB/YHvi85Ocs/pP7HQNCM/yZ0TQ8YBQLs44rz1md7oDDfSzKciB6qAzBl2iZ4nxAPRvHmv+Dku685Rz+u4kwwAV4gBdhfs7+svln+DyB+SlkQw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Only select ARCH_WANT_HUGE_PMD_SHARE on 64-bit x86. Page table sharing requires at least three levels because it involves shared references to PMD tables; 32-bit x86 has either two-level paging (without PAE) or three-level paging (with PAE), but even with three-level paging, having a dedicated PGD entry for hugetlb is only barely possible (because the PGD only has four entries), and it seems unlikely anyone's actually using PMD sharing on 32-bit. Having ARCH_WANT_HUGE_PMD_SHARE enabled on non-PAE 32-bit X86 (which has 2-level paging) became particularly problematic after commit 59d9094df3d7 ("mm: hugetlb: independent PMD page table shared count"), since that changes `struct ptdesc` such that the `pt_mm` (for PGDs) and the `pt_share_count` (for PMDs) share the same union storage - and with 2-level paging, PMDs are PGDs. (For comparison, arm64 also gates ARCH_WANT_HUGE_PMD_SHARE on the configuration of page tables such that it is never enabled with 2-level paging.) Reported-by: Vitaly Chikunov Closes: https://lore.kernel.org/r/srhpjxlqfna67blvma5frmy3aa@altlinux.org Suggested-by: Dave Hansen Tested-by: Vitaly Chikunov Fixes: cfe28c5d63d8 ("x86: mm: Remove x86 version of huge_pmd_share.") Cc: stable@vger.kernel.org Signed-off-by: Jann Horn --- I'm carrying over Vitaly Chikunov's "Tested-by" from v1. Changes in v2: - disable it for 32-bit entirely (Dave Hansen) - Link to v1: https://lore.kernel.org/r/20250630-x86-2level-hugetlb-v1-1-077cd53d8255@google.com --- arch/x86/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 71019b3b54ea..4e0fe688cc83 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -147,7 +147,7 @@ config X86 select ARCH_WANTS_DYNAMIC_TASK_STRUCT select ARCH_WANTS_NO_INSTR select ARCH_WANT_GENERAL_HUGETLB - select ARCH_WANT_HUGE_PMD_SHARE + select ARCH_WANT_HUGE_PMD_SHARE if X86_64 select ARCH_WANT_LD_ORPHAN_WARN select ARCH_WANT_OPTIMIZE_DAX_VMEMMAP if X86_64 select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64 --- base-commit: d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af change-id: 20250630-x86-2level-hugetlb-b1d8feb255ce -- Jann Horn