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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 AEFDAC00449 for ; Fri, 5 Oct 2018 13:42:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6D5BB2084D for ; Fri, 5 Oct 2018 13:42:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6D5BB2084D 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 S1728535AbeJEUlY (ORCPT ); Fri, 5 Oct 2018 16:41:24 -0400 Received: from foss.arm.com ([217.140.101.70]:52092 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727775AbeJEUlX (ORCPT ); Fri, 5 Oct 2018 16:41:23 -0400 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 79605ED1; Fri, 5 Oct 2018 06:42:36 -0700 (PDT) Received: from [10.4.13.99] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 126793F5B3; Fri, 5 Oct 2018 06:42:33 -0700 (PDT) Subject: Re: [PATCH] irqchip/gic-v3-its: Add early memory allocation errata To: Matthias Brugger , matthias.bgg@kernel.org, catalin.marinas@arm.com, will.deacon@arm.com, tglx@linutronix.de, jason@lakedaemon.net, robert.richter@cavium.com Cc: suzuki.poulose@arm.com, shankerd@codeaurora.org, xiexiuqi@huawei.com, Dave.Martin@arm.com, matthias.bgg@gmail.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20180912095232.2110-1-matthias.bgg@kernel.org> <95733d12-ee1d-9874-16a7-c614cc0ce8cd@arm.com> <8ef6b381-e170-30de-ad0e-fae8ccf189e5@suse.com> From: Marc Zyngier Organization: ARM Ltd Message-ID: <1d227152-2770-3e93-f78c-71e7a3b4fe76@arm.com> Date: Fri, 5 Oct 2018 14:42:32 +0100 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <8ef6b381-e170-30de-ad0e-fae8ccf189e5@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/10/18 13:33, Matthias Brugger wrote: > > > On 05/10/2018 12:55, Marc Zyngier wrote: >> Hi Matthias, >> >> On 04/10/18 23:11, Matthias Brugger wrote: >>> Friendly reminder, if anyone has any comment on the patch :) >>> >>> On 9/12/18 11:52 AM, matthias.bgg@kernel.org wrote: >>>> From: Matthias Brugger >>>> >>>> Some hardware does not implement two-level page tables so that >>>> the amount of contigious memory needed by the baser is bigger >>>> then the zone order. This is a known problem on Cavium Thunderx >>>> with 4K page size. >>>> >>>> We fix this by adding an errata which allocates the memory early >>>> in the boot cycle, using the memblock allocator. >>>> >>>> Signed-off-by: Matthias Brugger >>>> --- >>>>   arch/arm64/Kconfig               | 12 ++++++++ >>>>   arch/arm64/include/asm/cpucaps.h |  3 +- >>>>   arch/arm64/kernel/cpu_errata.c   | 33 +++++++++++++++++++++ >>>>   drivers/irqchip/irq-gic-v3-its.c | 50 ++++++++++++++++++++------------ >>>>   4 files changed, 79 insertions(+), 19 deletions(-) >> >> My only comment would be to state how much I dislike both the HW and the >> patch... ;-) The idea that we have some erratum that depends on the page size >> doesn't feel good at all. >> > > Well ugly HW needs ugly patches ;-) > >>>> >>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >>>> index 1b1a0e95c751..dfd9fe08f0b2 100644 >>>> --- a/arch/arm64/Kconfig >>>> +++ b/arch/arm64/Kconfig >>>> @@ -597,6 +597,18 @@ config QCOM_FALKOR_ERRATUM_E1041 >>>>           If unsure, say Y. >>>>   +config CAVIUM_ALLOC_ITS_TABLE_EARLY >>>> +    bool "Cavium Thunderx: Allocate the its table early" >>>> +    default y >>>> +    depends on ARM64_4K_PAGES && FORCE_MAX_ZONEORDER < 13 >> >> Here's a though: Why don't we ensure that FORCE_MAX_ZONEORDER is such as we >> could always allocate the same amount of memory, no matter what the page size >> is? That, or bump FORCE_MAX_ZONEORDER to 13 if the kernel includes support for TX1. >> > > Bumping FORCE_MAX_ZONEORDER when TX1 is supported was proposed here: > https://patchwork.kernel.org/patch/6322281/ > > To bring in some more history, the CMA approach ended with this discussion: > https://patchwork.kernel.org/patch/9888041/ > >> Any of this of course requires buy-in from the arm64 maintainers, as this is >> quite a departure from the way things work so far. >> > > With my distribution head on, I would prefer a solution that does not change > FORCE_MAX_ZONEORDER. That's how I came to the idea providing a third solution to > the same problem :) Why is that a problem? What impact does this have on your favourite distro? Thanks, M. -- Jazz is not dead. It just smells funny...