Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754604AbbHXNrP (ORCPT ); Mon, 24 Aug 2015 09:47:15 -0400 Received: from foss.arm.com ([217.140.101.70]:37319 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753921AbbHXNrO (ORCPT ); Mon, 24 Aug 2015 09:47:14 -0400 Message-ID: <55DB205E.9070205@arm.com> Date: Mon, 24 Aug 2015 14:47:10 +0100 From: Marc Zyngier Organization: ARM Ltd User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.7.0 MIME-Version: 1.0 To: Ganapatrao Kulkarni CC: Robert Richter , Will Deacon , Thomas Gleixner , Jason Cooper , "linux-arm-kernel@lists.infradead.org" , Tirumalesh Chalamarla , Robert Richter , "linux-kernel@vger.kernel.org" , Ganapatrao Kulkarni Subject: Re: [PATCH] irqchip, gicv3-its, numa: Workaround for Cavium ThunderX erratum 23144 References: <20150822131050.GK1820@rric.localdomain> <55DAEF3C.5090303@arm.com> <55DB11F3.1070604@arm.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2098 Lines: 52 On 24/08/15 14:27, Ganapatrao Kulkarni wrote: > On Mon, Aug 24, 2015 at 6:15 PM, Marc Zyngier wrote: >>>>> static void its_enable_cavium_thunderx(void *data) >>>>> { >>>>> - struct its_node *its = data; >>>>> + struct its_node __maybe_unused *its = data; >>>>> >>>>> - its->flags |= ITS_FLAGS_CAVIUM_THUNDERX; >>>>> +#ifdef CONFIG_CAVIUM_ERRATUM_22375 >>>>> + its->flags |= ITS_WORKAROUND_CAVIUM_22375; >>>>> + pr_info("ITS: Enabling workaround for 22375, 24313\n"); >>>>> +#endif >>>>> + >>>>> +#ifdef CONFIG_CAVIUM_ERRATUM_23144 >>>>> + if (num_possible_nodes() > 1) { >>>>> + its->numa_node = its_get_node_thunderx(its); >>>> >>>> I'd rather see numa_node being always initialized to something useful. >>>> If you're adding numa support, why can't this be initialized via >>>> standard topology bindings? >>> IIUC, topology defines only cpu topology. >> >> Well, welcome to a much more complex system where both your CPUs and >> your IOs have some degree of affinity. This needs to be described >> properly, and not hacked on the side. > ok, will add description for the function. I sense that you misunderstood what I meant. What I'd like to see is some topology information coming from DT, showing the relationship between a device (your ITS) and a given node (your socket). This can then be used from two purposes: - find the optimal affinity for a MSI so that it doesn't default to a foreign node (a reasonable performance expectation), - work around implementation bugs where an LPI cannot be routed to a redistributor that is on a foreign node. I really don't feel like adding a hack just for the second point, and I'd rather get the big picture right so that your workaround is just a special case of the generic one. Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/