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 41C18C4167D for ; Mon, 6 Nov 2023 23:24:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233710AbjKFXYl (ORCPT ); Mon, 6 Nov 2023 18:24:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234521AbjKFXYO (ORCPT ); Mon, 6 Nov 2023 18:24:14 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A197C3279; Mon, 6 Nov 2023 15:16:51 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AFB4EC43391; Mon, 6 Nov 2023 23:16:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699312611; bh=nYIgUtZGCGM2kQo8Pi+PUrGDpG7Ddh9yGmaawtxnl8E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G2UijwqRFEasgHLinUZrndWfzA88RTR98/rneGX47yzg7y6muj/Z3BnjhkWDM2/my MPi4ypi4HrR7LVWToM1/COQfFGzcaH0VDipCo4pK29n7Zi1Q6t3uirxqGEPVDaNzSq pfqZgdlDXeXyV2LDhJvg+y7bZj75ZBaRF0ufhcCFJIU1T6m/DRrtFvA96+PvwYWPh9 BSYgkDlPwssIQREti9LIZT3poNDjmFAFaPjkxk8UluF07eMBjxNUeqy5q/J7tZWFeM iwmKm45OmLVGeBIdDekA809Df7bEJIZYMs6KncWoJuReoxi0zByP9kNmbmIXXH3QO0 RVfOD/UvqrKig== 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 5.10 5/5] x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size Date: Mon, 6 Nov 2023 18:16:36 -0500 Message-ID: <20231106231639.3735753-5-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106231639.3735753-1-sashal@kernel.org> References: <20231106231639.3735753-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.10.199 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 9dc31996c7edb..62a119170376b 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_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