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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 0351FC0044C for ; Wed, 7 Nov 2018 15:44:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C0DFA20827 for ; Wed, 7 Nov 2018 15:44:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0DFA20827 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.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 S1729977AbeKHBPa (ORCPT ); Wed, 7 Nov 2018 20:15:30 -0500 Received: from foss.arm.com ([217.140.101.70]:53350 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727546AbeKHBPa (ORCPT ); Wed, 7 Nov 2018 20:15:30 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 00DCA80D; Wed, 7 Nov 2018 07:44:37 -0800 (PST) Received: from brain-police (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6793F3F5BD; Wed, 7 Nov 2018 07:44:36 -0800 (PST) Date: Wed, 7 Nov 2018 15:44:31 +0000 From: Will Deacon To: John Garry Cc: robh+dt@kernel.org, frowand.list@gmail.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linuxarm@huawei.com, anshuman.khandual@arm.com, peterz@infradead.org Subject: Re: [PATCH] of, numa: Validate some distance map rules Message-ID: <20181107154430.GA9996@brain-police> References: <1541507973-149965-1-git-send-email-john.garry@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1541507973-149965-1-git-send-email-john.garry@huawei.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? > 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 Will