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 BF3CBC00449 for ; Fri, 5 Oct 2018 12:34:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 796B52087D for ; Fri, 5 Oct 2018 12:34:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 796B52087D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.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 S1728356AbeJETcc (ORCPT ); Fri, 5 Oct 2018 15:32:32 -0400 Received: from smtp.nue.novell.com ([195.135.221.5]:60536 "EHLO smtp.nue.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727616AbeJETcc (ORCPT ); Fri, 5 Oct 2018 15:32:32 -0400 Received: from ziggy.stardust ([37.223.143.164]) by smtp.nue.novell.com with ESMTP (TLS encrypted); Fri, 05 Oct 2018 14:33:57 +0200 Subject: Re: [PATCH] irqchip/gic-v3-its: Add early memory allocation errata To: Marc Zyngier , 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> From: Matthias Brugger Openpgp: preference=signencrypt Autocrypt: addr=mbrugger@suse.com; prefer-encrypt=mutual; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <95733d12-ee1d-9874-16a7-c614cc0ce8cd@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/10/2018 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 :) Regards, Matthias