From nobody Tue Dec 16 17:13:41 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A9E0CDB474 for ; Fri, 20 Oct 2023 08:56:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376542AbjJTI44 (ORCPT ); Fri, 20 Oct 2023 04:56:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48388 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376520AbjJTI4x (ORCPT ); Fri, 20 Oct 2023 04:56:53 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED694D46; Fri, 20 Oct 2023 01:56:50 -0700 (PDT) Date: Fri, 20 Oct 2023 08:56:48 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1697792209; h=from:from:sender:sender:reply-to: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:in-reply-to:references:references; bh=/v7dhIVAF1zthVlRMitXiJdAtF/pjTP4sYxVNTwMQgs=; b=4h7yOK8OhGX1XBcsSKVCHpn/IR3HxKvNvqGg9jwawgxci0ePxe9Ut5ZzZvOp7U5+VfXzm+ F+WGCJUglWDRj9T38Q5lO6tEnr2368DLhM5BSsltr4KAzDCZHXbGadFU9sr3L5YxsTMB5g BWTJI7OaP2vQuuebKKfxp1zBxWUbWalqS3J9pHnEei3xfJyC/zsIqFuG+aKj3wpja9RrrH JUvdTkI6YunBVmzT0oeWHg8KITl+Imlh/H++tqG/WTorYuZYpr9Gq7OOwV2KAvnOuTl/Lp Lrm0dlS7nlyNEMWi5VERtPLXr5DuP9AazsWjmOjhT6W248rLtqFEbmEFMvJv1Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1697792209; h=from:from:sender:sender:reply-to: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:in-reply-to:references:references; bh=/v7dhIVAF1zthVlRMitXiJdAtF/pjTP4sYxVNTwMQgs=; b=pR9VQ/Dw41GsLseKmOFMsavXxaM2aDd2p0usLsboW/IoWeEjOL1E8iU56ynRpbP4QVortT 32BCKmge8zGKdXBQ== From: "tip-bot2 for Mike Rapoport (IBM)" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/mm] x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size Cc: Qi Zheng , Mario Casquero , "Mike Rapoport (IBM)" , Ingo Molnar , David Hildenbrand , Michal Hocko , Dave Hansen , Rik van Riel , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <867br@gmail.com> References: <867br@gmail.com> MIME-Version: 1.0 Message-ID: <169779220868.3135.10791045037524733897.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the x86/mm branch of tip: Commit-ID: a1e2b8b36820d8c91275f207e77e91645b7c6836 Gitweb: https://git.kernel.org/tip/a1e2b8b36820d8c91275f207e77e91645= b7c6836 Author: Mike Rapoport (IBM) AuthorDate: Wed, 18 Oct 2023 12:42:50 +02:00 Committer: Ingo Molnar CommitterDate: Fri, 20 Oct 2023 10:40:22 +02:00 x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size Qi Zheng reported crashes in a production environment and provided a simplified example as a reproducer: | For example, if we use Qemu to start a two NUMA node kernel, | one of the nodes has 2M memory (less than NODE_MIN_SIZE), | and the other node has 2G, then we will encounter the | following panic: | | BUG: kernel NULL pointer dereference, address: 0000000000000000 | <...> | RIP: 0010:_raw_spin_lock_irqsave+0x22/0x40 | <...> | Call Trace: | | deactivate_slab() | bootstrap() | kmem_cache_init() | start_kernel() | secondary_startup_64_no_verify() The crashes happen because of inconsistency between the nodemask that has nodes with less than 4MB as memoryless, and the actual memory fed into the core mm. The commit: 9391a3f9c7f1 ("[PATCH] x86_64: Clear more state when ignoring empty node = in SRAT parsing") ... that introduced minimal size of a NUMA node does not explain why a node size cannot be less than 4MB and what boot failures this restriction might fix. Fixes have been submitted to the core MM code to tighten up the memory topologies it accepts and to not crash on weird input: mm: page_alloc: skip memoryless nodes entirely mm: memory_hotplug: drop memoryless node from fallback lists Andrew has accepted them into the -mm tree, but there are no stable SHA1's yet. This patch drops the limitation for minimal node size on x86: - which works around the crash without the fixes to the core MM. - makes x86 topologies less weird, - removes an arbitrary and undocumented limitation on NUMA topologies. [ mingo: Improved changelog clarity. ] Reported-by: Qi Zheng Tested-by: Mario Casquero Signed-off-by: Mike Rapoport (IBM) Signed-off-by: Ingo Molnar Acked-by: David Hildenbrand Acked-by: Michal Hocko Cc: Dave Hansen Cc: Rik van Riel Link: https://lore.kernel.org/r/ZS+2qqjEO5/867br@gmail.com --- arch/x86/include/asm/numa.h | 7 ------- arch/x86/mm/numa.c | 7 ------- 2 files changed, 14 deletions(-) diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h index e3bae2b..ef2844d 100644 --- a/arch/x86/include/asm/numa.h +++ b/arch/x86/include/asm/numa.h @@ -12,13 +12,6 @@ =20 #define NR_NODE_MEMBLKS (MAX_NUMNODES*2) =20 -/* - * Too small node sizes may confuse the VM badly. Usually they - * result from BIOS bugs. So dont recognize nodes as standalone - * NUMA entities that have less than this amount of RAM listed: - */ -#define NODE_MIN_SIZE (4*1024*1024) - extern int numa_off; =20 /* diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c index c01c550..aa39d67 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -602,13 +602,6 @@ static int __init numa_register_memblks(struct numa_me= minfo *mi) if (start >=3D end) continue; =20 - /* - * Don't confuse VM with a node that doesn't have the - * minimum amount of memory: - */ - if (end && (end - start) < NODE_MIN_SIZE) - continue; - alloc_node_data(nid); }