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 8A108C4167D for ; Mon, 6 Nov 2023 23:17:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233431AbjKFXRY (ORCPT ); Mon, 6 Nov 2023 18:17:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233639AbjKFXQl (ORCPT ); Mon, 6 Nov 2023 18:16:41 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCDA4212D; Mon, 6 Nov 2023 15:15:44 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BC3B5C433C8; Mon, 6 Nov 2023 23:15:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699312544; bh=LO4hMTKUYKEyxNtgfrH8fljSkWOJqgcyCWbJec+fCtU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EjxUKW/XPr1kKEnoemDmi+JbLDztAfofijTD6ZN/lKJYzHYg/xqKLnvVMiggG87vL 4XduvWJIS2mvkwb7hP7l5PPBBGzegULKfmC4Az54ioaiIJjMVUnT8gZZeTJRfYGrAY VfwJSeSPug6AsT51oeeWLoB7K2YUW98zS88t2cCxKeYD3YbKVShkkykvSN9MXuRCnr p/rChto+JfNyx+nm0jxHnaqC/sDhv2fREdRZG1WhG8zl79NUES0QjjyaDKTKjDLBe8 WKRxeCyECehUgggaRr0B5cFTLtUsHOOl0sUmL/3ff4dOgcEOLXNJHJ/dEPBVfek1e2 HV9uezaHmMo7A== 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 6.5 13/13] x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size Date: Mon, 6 Nov 2023 18:15:06 -0500 Message-ID: <20231106231514.3735077-13-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106231514.3735077-1-sashal@kernel.org> References: <20231106231514.3735077-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.5.10 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 e3bae2b60a0db..ef2844d691735 100644 --- a/arch/x86/include/asm/numa.h +++ b/arch/x86/include/asm/numa.h @@ -12,13 +12,6 @@ #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 2aadb2019b4f2..55e3d895f15c3 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -601,13 +601,6 @@ 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