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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 536C1C3A59B for ; Mon, 2 Sep 2019 05:47:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2069121897 for ; Mon, 2 Sep 2019 05:47:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729503AbfIBFrh (ORCPT ); Mon, 2 Sep 2019 01:47:37 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:5706 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729403AbfIBFrh (ORCPT ); Mon, 2 Sep 2019 01:47:37 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 841D5224CEFB5C28D060; Mon, 2 Sep 2019 13:47:28 +0800 (CST) Received: from [127.0.0.1] (10.74.191.121) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.439.0; Mon, 2 Sep 2019 13:47:19 +0800 Subject: Re: [PATCH v2 2/9] x86: numa: check the node id consistently for x86 To: Peter Zijlstra CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 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> From: Yunsheng Lin Message-ID: Date: Mon, 2 Sep 2019 13:46:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20190831161247.GM2369@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.74.191.121] X-CFilter-Loop: Reflected Sender: linux-mips-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org Archived-At: List-Archive: List-Post: On 2019/9/1 0:12, Peter Zijlstra wrote: > On Sat, Aug 31, 2019 at 06:09:39PM +0800, Yunsheng Lin wrote: >> >> >> On 2019/8/31 16:55, Peter Zijlstra wrote: >>> On Sat, Aug 31, 2019 at 01:58:16PM +0800, Yunsheng Lin wrote: >>>> According to Section 6.2.14 from ACPI spec 6.3 [1], the setting >>>> of proximity domain is optional, as below: >>>> >>>> This optional object is used to describe proximity domain >>>> associations within a machine. _PXM evaluates to an integer >>>> that identifies a device as belonging to a Proximity Domain >>>> defined in the System Resource Affinity Table (SRAT). >>> >>> That's just words.. what does it actually mean? >> >> It means the dev_to_node(dev) may return -1 if the bios does not >> implement the proximity domain feature, user may use that value >> to call cpumask_of_node and cpumask_of_node does not protect itself >> from node id being -1, which causes out of bound access. > >>>> @@ -69,6 +69,12 @@ extern const struct cpumask *cpumask_of_node(int node); >>>> /* Returns a pointer to the cpumask of CPUs on Node 'node'. */ >>>> static inline const struct cpumask *cpumask_of_node(int node) >>>> { >>>> + if (node >= nr_node_ids) >>>> + return cpu_none_mask; >>>> + >>>> + if (node < 0 || !node_to_cpumask_map[node]) >>>> + return cpu_online_mask; >>>> + >>>> return node_to_cpumask_map[node]; >>>> } >>>> #endif >>> >>> I _reallly_ hate this. Users are expected to use valid numa ids. Now >>> we're adding all this checking to all users. Why do we want to do that? >> >> As above, the dev_to_node(dev) may return -1. >> >>> >>> Using '(unsigned)node >= nr_nods_ids' is an error. >> >> 'node >= nr_node_ids' can be dropped if all user is expected to not call >> cpumask_of_node with node id greater or equal to nr_nods_ids. > > you copied my typo :-) I did note the typo, corrected the first one, but missed the second one :) > >> From what I can see, the problem can be fixed in three place: >> 1. Make user dev_to_node return a valid node id even when proximity >> domain is not set by bios(or node id set by buggy bios is not valid), >> which may need info from the numa system to make sure it will return >> a valid node. >> >> 2. User that call cpumask_of_node should ensure the node id is valid >> before calling cpumask_of_node, and user also need some info to >> make ensure node id is valid. >> >> 3. Make sure cpumask_of_node deal with invalid node id as this patchset. >> >> Which one do you prefer to make sure node id is valid, or do you >> have any better idea? >> >> Any detail advice and suggestion will be very helpful, thanks. > > 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? > > 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. > > 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()? > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . >