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=-5.5 required=3.0 tests=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 62396CA9EC5 for ; Wed, 30 Oct 2019 11:36:16 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D639B2083E for ; Wed, 30 Oct 2019 11:36:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D639B2083E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4735xn1ZPnzDqTW for ; Wed, 30 Oct 2019 22:36:13 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=softfail (domain owner discourages use of this host) smtp.mailfrom=kernel.org (client-ip=195.135.220.15; helo=mx1.suse.de; envelope-from=mhocko@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=fail (p=none dis=none) header.from=kernel.org Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4735tm3Qd8zF3xh for ; Wed, 30 Oct 2019 22:33:36 +1100 (AEDT) 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 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) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dalias@libc.org, linux-sh@vger.kernel.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, heiko.carstens@de.ibm.com, jiaxun.yang@flygoat.com, linux-mips@vger.kernel.org, mwb@linux.vnet.ibm.com, paulus@samba.org, hpa@zytor.com, sparclinux@vger.kernel.org, chenhc@lemote.com, will@kernel.org, cai@lca.pw, linux-s390@vger.kernel.org, ysato@users.sourceforge.jp, linux-acpi@vger.kernel.org, x86@kernel.org, Yunsheng Lin , rppt@linux.ibm.com, borntraeger@de.ibm.com, dledford@redhat.com, mingo@redhat.com, jeffrey.t.kirsher@intel.com, jhogan@kernel.org, mattst88@gmail.com, lenb@kernel.org, len.brown@intel.com, gor@linux.ibm.com, anshuman.khandual@arm.com, gregkh@linuxfoundation.org, bp@alien8.de, luto@kernel.org, bhelgaas@google.com, tglx@linutronix.de, naveen.n.rao@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org, rth@twiddle.net, axboe@kernel.dk, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, ralf@linux-mips.org, tbogendoerfer@suse.de, paul.burton@mips.com, linux-alpha@vger.kernel.org, rafael@kernel.org, ink@jurassic.park.msu.ru, akpm@linux-foundation.org, robin.murphy@arm.com, davem@davemloft.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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