From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:43144 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725851AbfIWPRQ (ORCPT ); Mon, 23 Sep 2019 11:17:16 -0400 Date: Mon, 23 Sep 2019 17:15:19 +0200 From: Peter Zijlstra Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware Message-ID: <20190923151519.GE2369@hirez.programming.kicks-ass.net> References: <1568724534-146242-1-git-send-email-linyunsheng@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1568724534-146242-1-git-send-email-linyunsheng@huawei.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Yunsheng Lin Cc: 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, mhocko@kernel.org, gregkh@linuxfoundation.org On Tue, Sep 17, 2019 at 08:48:54PM +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://lore.kernel.org/patchwork/patch/1125789/ That is bloody unusable, don't do that. Use: https://lkml.kernel.org/r/$MSGID if anything. Then I can find it in my local mbox without having to resort to touching a mouse and shitty browser software. (also patchwork is absolute crap for reading email threads) Anyway, I found it -- I think, I refused to click the link. I replied there. > Signed-off-by: Yunsheng Lin > Suggested-by: Michal Hocko > Acked-by: Michal Hocko > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c > index 4123100e..9859acb 100644 > --- a/arch/x86/mm/numa.c > +++ b/arch/x86/mm/numa.c > @@ -861,6 +861,9 @@ void numa_remove_cpu(int cpu) > */ > const struct cpumask *cpumask_of_node(int node) > { > + if (node == NUMA_NO_NODE) > + return cpu_online_mask; This mandates the caller holds cpus_read_lock() or something, I'm pretty sure that if I put: lockdep_assert_cpus_held(); here, it comes apart real quick. Without holding the cpu hotplug lock, the online mask is gibberish. > + > if ((unsigned)node >= nr_node_ids) { > printk(KERN_WARNING > "cpumask_of_node(%d): (unsigned)node >= nr_node_ids(%u)\n", I still think this makes absolutely no sense what so ever.