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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham 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 52B13C0044C for ; Wed, 7 Nov 2018 16:25:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2215020827 for ; Wed, 7 Nov 2018 16:25:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2215020827 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731401AbeKHB4F (ORCPT ); Wed, 7 Nov 2018 20:56:05 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:47602 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727372AbeKHB4F (ORCPT ); Wed, 7 Nov 2018 20:56:05 -0500 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 8D64912FE9D66; Thu, 8 Nov 2018 00:24:58 +0800 (CST) Received: from [127.0.0.1] (10.202.226.41) by DGGEMS402-HUB.china.huawei.com (10.3.19.202) with Microsoft SMTP Server id 14.3.408.0; Thu, 8 Nov 2018 00:24:50 +0800 Subject: Re: [PATCH] of, numa: Validate some distance map rules To: Rob Herring , Will Deacon References: <1541507973-149965-1-git-send-email-john.garry@huawei.com> <20181107154430.GA9996@brain-police> <20181107155552.GB18618@bogus> CC: , , , , , From: John Garry Message-ID: <5b81e832-4ad0-13f2-1857-0764d175c61b@huawei.com> Date: Wed, 7 Nov 2018 16:24:45 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <20181107155552.GB18618@bogus> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.226.41] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/11/2018 15:55, Rob Herring wrote: > On Wed, Nov 07, 2018 at 03:44:31PM +0000, Will Deacon wrote: >> Hi John, >> >> On Tue, Nov 06, 2018 at 08:39:33PM +0800, John Garry wrote: >>> Currently the NUMA distance map parsing does not validate the distance >>> table for the distance-matrix rules 1-2 in [1]. >>> >>> However the arch NUMA code may enforce some of these rules, but not all. >>> Such is the case for the arm64 port, which does not enforce the rule that >>> the distance between separates nodes cannot equal LOCAL_DISTANCE. >>> >>> The patch adds the following rules validation: >>> - distance of node to self equals LOCAL_DISTANCE >>> - distance of separate nodes > LOCAL_DISTANCE >>> >>> A note on dealing with symmetrical distances between nodes: >>> >>> Validating symmetrical distances between nodes is difficult. If it were >>> mandated in the bindings that every distance must be recorded in the >>> table, validating symmetrical distances would be straightforward. However, >>> it isn't. >>> >>> In addition to this, it is also possible to record [b, a] distance only >>> (and not [a, b]). So, when processing the table for [b, a], we cannot >>> assert that current distance of [a, b] != [b, a] as invalid, as [a, b] >>> distance may not be present in the table and current distance would be >>> default at REMOTE_DISTANCE. >>> >>> As such, we maintain the policy that we overwrite distance [a, b] = [b, a] >>> for b > a. This policy is different to kernel ACPI SLIT validation, which >>> allows non-symmetrical distances (ACPI spec SLIT rules allow it). However, >>> the debug message is dropped as it may be misleading (for a distance which >>> is later overwritten). >>> >>> Some final notes on semantics: >>> >>> - It is implied that it is the responsibility of the arch NUMA code to >>> reset the NUMA distance map for an error in distance map parsing. >>> >>> - It is the responsibility of the FW NUMA topology parsing (whether OF or >>> ACPI) to enforce NUMA distance rules, and not arch NUMA code. >>> >>> [1] Documents/devicetree/bindings/numa.txt >>> >>> Signed-off-by: John Garry >> >> Is it worth mentioning that the lack of this check was leading to a kernel >> crash with a malformed DT entry? Yeah, I was thinking in hindsight that I should have mentioned the yet-unresolved crash we avoid. > > So should be marked for stable too? Probably. So this patch is masking a crash I have observed, which may be good enough reason on its own. In addition, I would still say that failing to validate the distance map falls into the "oh, that's not good" category of stable rules. > >> >>> diff --git a/drivers/of/of_numa.c b/drivers/of/of_numa.c >>> index 35c64a4295e0..fe6b13608e51 100644 >>> --- a/drivers/of/of_numa.c >>> +++ b/drivers/of/of_numa.c >>> @@ -104,9 +104,14 @@ static int __init of_numa_parse_distance_map_v1(struct device_node *map) >>> distance = of_read_number(matrix, 1); >>> matrix++; >>> >>> + if ((nodea == nodeb && distance != LOCAL_DISTANCE) || >>> + (nodea != nodeb && distance <= LOCAL_DISTANCE)) { >>> + pr_err("Invalid distance[node%d -> node%d] = %d\n", >>> + nodea, nodeb, distance); >>> + return -EINVAL; >>> + } >>> + >>> numa_set_distance(nodea, nodeb, distance); >>> - pr_debug("distance[node%d -> node%d] = %d\n", >>> - nodea, nodeb, distance); >> >> Looks good to me, although I'm not sure which tree this should go through. >> >> Acked-by: Will Deacon > Thanks Will. > I'll take it. Please resend with the comment Will asked for. > OK, I'll repost an updated version. > Rob > Cheers, john > . >