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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 44042C3A5A8 for ; Mon, 2 Sep 2019 07:29:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1BDD723774 for ; Mon, 2 Sep 2019 07:29:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="RSg8SK30" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729783AbfIBH3y (ORCPT ); Mon, 2 Sep 2019 03:29:54 -0400 Received: from merlin.infradead.org ([205.233.59.134]:42206 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729408AbfIBH3y (ORCPT ); Mon, 2 Sep 2019 03:29:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=kuvYA3T0maxhdGUw985D46q7bOf4rHWESmnw46BzIyU=; b=RSg8SK30rWjj+TGxS+skngBb9 2fH0Zbvox/26y8ns9l17onRj+Z0upMjen1Jy9C225gpAYncbszcWwsNoaRVXtRhycw5sQPRXxvqZF MZcgdzGUMBphpdnOn16uYyMgLt+qN6EW1z0DTDeFTlEiZTt3odbqEu+DJSqCou9wwYKKH0FxT6dWN I+zp9Ai4QHlNhoBhF21uUvEYbhfjZl2GTj5O4kluEqPaq3MIV3nvvVSecP3gXpoqPTIw8UHW+LeG+ 00NHCbD42nXGQS4hidMqlBA/pQDia+x5u1X7c5K0Y5fMyiWYIiSoxiwz3DDXxm0RHe9+pK3isf+sd NVR1Me1xA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1i4gik-0004XZ-Fx; Mon, 02 Sep 2019 07:25:50 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 6DC0530116F; Mon, 2 Sep 2019 09:25:06 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 1636C29B6185F; Mon, 2 Sep 2019 09:25:42 +0200 (CEST) Date: Mon, 2 Sep 2019 09:25:42 +0200 From: Peter Zijlstra To: Yunsheng Lin Cc: dalias@libc.org, linux-sh@vger.kernel.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, heiko.carstens@de.ibm.com, linuxarm@huawei.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, mpe@ellerman.id.au, x86@kernel.org, rppt@linux.ibm.com, borntraeger@de.ibm.com, dledford@redhat.com, mingo@redhat.com, jeffrey.t.kirsher@intel.com, benh@kernel.crashing.org, jhogan@kernel.org, nfont@linux.vnet.ibm.com, mattst88@gmail.com, len.brown@intel.com, gor@linux.ibm.com, anshuman.khandual@arm.com, bp@alien8.de, luto@kernel.org, tglx@linutronix.de, naveen.n.rao@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org, rth@twiddle.net, axboe@kernel.dk, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, ralf@linux-mips.org, tbogendoerfer@suse.de, paul.burton@mips.com, linux-alpha@vger.kernel.org, ink@jurassic.park.msu.ru, akpm@linux-foundation.org, robin.murphy@arm.com, davem@davemloft.net Subject: Re: [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Message-ID: <20190902072542.GN2369@hirez.programming.kicks-ass.net> References: <1567231103-13237-1-git-send-email-linyunsheng@huawei.com> <1567231103-13237-3-git-send-email-linyunsheng@huawei.com> <20190831085539.GG2369@hirez.programming.kicks-ass.net> <4d89c688-49e4-a2aa-32ee-65e36edcd913@huawei.com> <20190831161247.GM2369@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, Sep 02, 2019 at 01:46:51PM +0800, Yunsheng Lin wrote: > On 2019/9/1 0:12, Peter Zijlstra wrote: > > 1) because even it is not set, the device really does belong to a node. > > It is impossible a device will have magic uniform access to memory when > > CPUs cannot. > > So it means dev_to_node() will return either NUMA_NO_NODE or a > valid node id? NUMA_NO_NODE := -1, which is not a valid node number. It is also, like I said, not a valid device location on a NUMA system. Just because ACPI/BIOS is shit, doesn't mean the device doesn't have a node association. It just means we don't know and might have to guess. > > 2) is already true today, cpumask_of_node() requires a valid node_id. > > Ok, most of the user does check node_id before calling > cpumask_of_node(), but does a little different type of checking: > > 1) some does " < 0" check; > 2) some does "== NUMA_NO_NODE" check; > 3) some does ">= MAX_NUMNODES" check; > 4) some does "< 0 || >= MAX_NUMNODES || !node_online(node)" check. The one true way is: '(unsigned)node_id >= nr_node_ids' > > 3) is just wrong and increases overhead for everyone. > > Ok, cpumask_of_node() is also used in some critical path such > as scheduling, which may not need those checking, the overhead > is unnecessary. > > But for non-critical path such as setup or configuration path, > it better to have consistent checking, and also simplify the > user code that calls cpumask_of_node(). > > Do you think it is worth the trouble to add a new function > such as cpumask_of_node_check(maybe some other name) to do > consistent checking? > > Or caller just simply check if dev_to_node()'s return value is > NUMA_NO_NODE before calling cpumask_of_node()? It is not a matter of convenience. The function is called cpumask_of_node(), when node < 0 || node >= nr_node_ids, it is not a valid node, therefore the function shouldn't return anything except an error. Also note that the CONFIG_DEBUG_PER_CPU_MAPS version of cpumask_of_node() already does this (although it wants the below fix). --- diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c index e6dad600614c..5f49c10201c7 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -861,7 +861,7 @@ void numa_remove_cpu(int cpu) */ const struct cpumask *cpumask_of_node(int node) { - if (node >= nr_node_ids) { + if ((unsigned)node >= nr_node_ids) { printk(KERN_WARNING "cpumask_of_node(%d): node > nr_node_ids(%u)\n", node, nr_node_ids);