From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 253EE3306F; Fri, 24 Nov 2023 19:22:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="EQyKm7mj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1536AC433C8; Fri, 24 Nov 2023 19:22:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700853743; bh=GSh6zGcHe751DCQwy2F3U3ZwggB5C0ieqcDfEge8cmk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EQyKm7mjS0N90ppHMcrHQ+O6ln9uiDSHKPHde2gVTOWMIWeaI1PDNLniaEO0uKCVz qdla80zBo2xWiPdZy16RVswJNMzHJO/31YtudvH5o0jEQ47CgXr2ZhlfqXWrvsCx8K PC9tCRTZEdPOqSE/oPYFM3WoAN7Ywgg8LAE5c+gQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Qi Zheng , Mario Casquero , "Mike Rapoport (IBM)" , Ingo Molnar , David Hildenbrand , Michal Hocko , Dave Hansen , Rik van Riel , Sasha Levin Subject: [PATCH 5.4 005/159] x86/mm: Drop the 4 MB restriction on minimal NUMA node memory size Date: Fri, 24 Nov 2023 17:53:42 +0000 Message-ID: <20231124171942.129997117@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124171941.909624388@linuxfoundation.org> References: <20231124171941.909624388@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ 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