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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 881DEC4167B for ; Mon, 6 Nov 2023 23:23:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234136AbjKFXXd (ORCPT ); Mon, 6 Nov 2023 18:23:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233886AbjKFXXN (ORCPT ); Mon, 6 Nov 2023 18:23:13 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C4393AA3; Mon, 6 Nov 2023 15:17:09 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D142C116B0; Mon, 6 Nov 2023 23:17:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699312628; bh=g58stcoxTrEGJ7ZwubRe4Xu7OraTh6PKY/BU1DJAdyM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VwC3sqqC08t3o+NcEkmuKjUjMPNSzeYBmQQf9LuSE4pXqMBZSR7E7yC3RdkR9w2TI kXmq5M8Vc8NitLqG7yDf1chm3mJ/WMLgaSS2MfjOk4SNkD18KCZtRheKJ0nqYiE9Lo mezNgvsleV5yMnNuLWny+IehdT2QV8jTyocHyxMSGm4/Xovwu0uGn1mlV/XhJlQymd baHRMUkkb1vGyoOnPRGQTZFT+tvhB1F3aZf3rCq77b45Nx5pqIBOm3AisSQLhNasrG zA2XLwyXxaEcksCe0eihSMwXMe9A/ryWR1qmN8yliZP197MPkVmN1sTchuHbF+yc3l QWbVchj46YiRA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Mike Rapoport (IBM)" , Qi Zheng , Mario Casquero , Ingo Molnar , David Hildenbrand , Michal Hocko , Dave Hansen , Rik van Riel , Sasha Levin , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, luto@kernel.org, peterz@infradead.org Subject: [PATCH AUTOSEL 5.4 5/5] x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size Date: Mon, 6 Nov 2023 18:16:52 -0500 Message-ID: <20231106231655.3735872-5-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106231655.3735872-1-sashal@kernel.org> References: <20231106231655.3735872-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.4.259 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Mike Rapoport (IBM)" [ Upstream commit a1e2b8b36820d8c91275f207e77e91645b7c6836 ] 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 Signed-off-by: Sasha Levin --- 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 bbfde3d2662f4..4bcd9d0c7bee7 100644 --- a/arch/x86/include/asm/numa.h +++ b/arch/x86/include/asm/numa.h @@ -11,13 +11,6 @@ #define NR_NODE_MEMBLKS (MAX_NUMNODES*2) -/* - * 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; /* diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c index 67c617c4a7f20..7316dca7e846a 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -581,13 +581,6 @@ static int __init numa_register_memblks(struct numa_meminfo *mi) if (start >= end) continue; - /* - * 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); } -- 2.42.0