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 5AD8BCDB483 for ; Tue, 17 Oct 2023 07:53:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234683AbjJQHxF (ORCPT ); Tue, 17 Oct 2023 03:53:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59732 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234608AbjJQHxD (ORCPT ); Tue, 17 Oct 2023 03:53:03 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A4A2AB for ; Tue, 17 Oct 2023 00:53:01 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA132C433C7; Tue, 17 Oct 2023 07:52:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1697529180; bh=p4vpHmypakCe2FUK/2r5Z+O00L713pYXDijPBBsNJtM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=n3EcTVMYCp1luKu0MYqwDlTz6z3NwwAlbckflCa9SjThkR/IQPIVbYCG+RfqHTCP/ NPKfhTe7AKTD+QNo720QTt4hZ0/Zg5pZ8QJtEt87QHVB2DRB+S3s9IgWtHHNbkK0rd ftudnKKxgDiZ2Nkn9mWsAQv6u/NqfEfQb6q+4Q6TqSDuA9CX1iyJVfHkR+GNpH9ZuF 5swsQ9Y33VQI0JjskK79q5EYN8flWzVZ2hdrR5Zy2GbELOrfissMawNbqQXN6jBLgO x4AA6/EZ+3BlnN+nCEUxmNsnb4v2K5Coz321wwvQOffPpUg2XGbecOKJO5jnnBKn2H /tC5gCkMjhaSg== Date: Tue, 17 Oct 2023 10:52:46 +0300 From: Mike Rapoport To: David Hildenbrand Cc: x86@kernel.org, Andrew Morton , Andy Lutomirski , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Ingo Molnar , Michal Hocko , Peter Zijlstra , Qi Zheng , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] x86/mm: drop 4MB restriction on minimal NUMA node size Message-ID: <20231017075246.GA2824@kernel.org> References: <20231017062215.171670-1-rppt@kernel.org> <4207feb8-be8c-4d49-b880-31366c0414cb@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4207feb8-be8c-4d49-b880-31366c0414cb@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 17, 2023 at 09:28:14AM +0200, David Hildenbrand wrote: > On 17.10.23 08:22, Mike Rapoport wrote: > > From: "Mike Rapoport (IBM)" > > > > Qi Zheng reports crashes in a production environment and provides 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: > > > > [ 0.149844] BUG: kernel NULL pointer dereference, address: 0000000000000000 > > [ 0.150783] #PF: supervisor write access in kernel mode > > [ 0.151488] #PF: error_code(0x0002) - not-present page > > <...> > > [ 0.156056] RIP: 0010:_raw_spin_lock_irqsave+0x22/0x40 > > <...> > > [ 0.169781] Call Trace: > > [ 0.170159] > > [ 0.170448] deactivate_slab+0x187/0x3c0 > > [ 0.171031] ? bootstrap+0x1b/0x10e > > [ 0.171559] ? preempt_count_sub+0x9/0xa0 > > [ 0.172145] ? kmem_cache_alloc+0x12c/0x440 > > [ 0.172735] ? bootstrap+0x1b/0x10e > > [ 0.173236] bootstrap+0x6b/0x10e > > [ 0.173720] kmem_cache_init+0x10a/0x188 > > [ 0.174240] start_kernel+0x415/0x6ac > > [ 0.174738] secondary_startup_64_no_verify+0xe0/0xeb > > [ 0.175417] > > [ 0.175713] Modules linked in: > > [ 0.176117] CR2: 0000000000000000 > > > > The crashes happen because of inconsistency between nodemask that has > > nodes with less than 4MB as memoryless and the actual memory fed into > > 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. > > > > Since then a lot has changed and core mm won't confuse badly about small > > node sizes. > > > > Drop the limitation for the minimal node size. > > > > Reported-by: Qi Zheng > > Signed-off-by: Mike Rapoport (IBM) > > Acked-by: David Hildenbrand > > Acked-by: Michal Hocko > > Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > > That's just a resend I assume? Or has anything changed? Oh, I forgot RESEND prefix, sorry > -- > Cheers, > > David / dhildenb > -- Sincerely yours, Mike.