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 X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8623ACA9EC7 for ; Wed, 30 Oct 2019 11:33:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 604592083E for ; Wed, 30 Oct 2019 11:33:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572435217; bh=fnnpfaC9BEEar7C5BqFB3BIb9m+9ZYBV8LUNLwzwOes=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=CU0A9vL2dtUDMaoaZk82hygyXPrU8gMDXL6c1h/im/OByqYT19AWU+09OAB8odudE oLLKix7CF53oS6KM1aQChWeMYn3sZyySKZm0aJPOpqgjG8IyerhN0VhL4QuRiAl7/3 EHOPIh7MozRCEZuJyLlxEm5HW+CAP77RWnD8MK4I= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726488AbfJ3Ldg (ORCPT ); Wed, 30 Oct 2019 07:33:36 -0400 Received: from mx2.suse.de ([195.135.220.15]:52524 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726225AbfJ3Ldg (ORCPT ); Wed, 30 Oct 2019 07:33:36 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 09DEAADDD; Wed, 30 Oct 2019 11:33:32 +0000 (UTC) Date: Wed, 30 Oct 2019 12:33:28 +0100 From: Michal Hocko To: Peter Zijlstra Cc: Yunsheng Lin , catalin.marinas@arm.com, will@kernel.org, mingo@redhat.com, bp@alien8.de, rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, heiko.carstens@de.ibm.com, gor@linux.ibm.com, borntraeger@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, ralf@linux-mips.org, paul.burton@mips.com, jhogan@kernel.org, jiaxun.yang@flygoat.com, chenhc@lemote.com, akpm@linux-foundation.org, rppt@linux.ibm.com, anshuman.khandual@arm.com, tglx@linutronix.de, cai@lca.pw, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, len.brown@intel.com, axboe@kernel.dk, dledford@redhat.com, jeffrey.t.kirsher@intel.com, linux-alpha@vger.kernel.org, naveen.n.rao@linux.vnet.ibm.com, mwb@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, tbogendoerfer@suse.de, linux-mips@vger.kernel.org, rafael@kernel.org, gregkh@linuxfoundation.org, bhelgaas@google.com, linux-pci@vger.kernel.org, rjw@rjwysocki.net, lenb@kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH v7] numa: make node_to_cpumask_map() NUMA_NO_NODE aware Message-ID: <20191030113328.GA31513@dhcp22.suse.cz> References: <1572428068-180880-1-git-send-email-linyunsheng@huawei.com> <20191030101449.GW4097@hirez.programming.kicks-ass.net> <20191030102229.GY31513@dhcp22.suse.cz> <20191030102800.GX4097@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191030102800.GX4097@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 30-10-19 11:28:00, Peter Zijlstra wrote: > On Wed, Oct 30, 2019 at 11:22:29AM +0100, Michal Hocko wrote: > > On Wed 30-10-19 11:14:49, Peter Zijlstra wrote: > > > On Wed, Oct 30, 2019 at 05:34:28PM +0800, Yunsheng Lin wrote: > > > > When passing the return value of dev_to_node() to cpumask_of_node() > > > > without checking if the device's node id is NUMA_NO_NODE, there is > > > > global-out-of-bounds detected by KASAN. > > > > > > > > From the discussion [1], NUMA_NO_NODE really means no node affinity, > > > > which also means all cpus should be usable. So the cpumask_of_node() > > > > should always return all cpus online when user passes the node id as > > > > NUMA_NO_NODE, just like similar semantic that page allocator handles > > > > NUMA_NO_NODE. > > > > > > > > But we cannot really copy the page allocator logic. Simply because the > > > > page allocator doesn't enforce the near node affinity. It just picks it > > > > up as a preferred node but then it is free to fallback to any other numa > > > > node. This is not the case here and node_to_cpumask_map will only restrict > > > > to the particular node's cpus which would have really non deterministic > > > > behavior depending on where the code is executed. So in fact we really > > > > want to return cpu_online_mask for NUMA_NO_NODE. > > > > > > > > Also there is a debugging version of node_to_cpumask_map() for x86 and > > > > arm64, which is only used when CONFIG_DEBUG_PER_CPU_MAPS is defined, this > > > > patch changes it to handle NUMA_NO_NODE as normal node_to_cpumask_map(). > > > > > > > > [1] https://lkml.org/lkml/2019/9/11/66 > > > > Signed-off-by: Yunsheng Lin > > > > Suggested-by: Michal Hocko > > > > Acked-by: Michal Hocko > > > > Acked-by: Paul Burton # MIPS bits > > > > > > Still: > > > > > > Nacked-by: Peter Zijlstra (Intel) > > > > Do you have any other proposal that doesn't make any wild guesses about > > which node to use instead of the undefined one? > > It only makes 'wild' guesses when the BIOS is shit and it complains > about that. I really do not see how this is any better than simply using the online cpu mask in the same "broken" situation. We are effectivelly talking about a suboptimal path for suboptimal setups. I haven't heard any actual technical argument why cpu_online_mask is any worse than adding some sort of failover guessing which node to use as a replacement. I completely do you point about complaining loud about broken BIOS/fw. It seems we just disagree where we should workaround those issues because as of now we simply do generate semi random behavior because of an uninitialized memory access. > Or do you like you BIOS broken? I do not see anything like that in my response nor in my previous communication. Moreover a patch to warn about this should be on the way to get merged AFAIK. -- Michal Hocko SUSE Labs