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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 6453DC282CE for ; Tue, 9 Apr 2019 05:20:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D67620883 for ; Tue, 9 Apr 2019 05:20:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726837AbfDIFU0 (ORCPT ); Tue, 9 Apr 2019 01:20:26 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:44572 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725550AbfDIFUZ (ORCPT ); Tue, 9 Apr 2019 01:20:25 -0400 Received: by mail-pl1-f196.google.com with SMTP id g12so8649800pll.11 for ; Mon, 08 Apr 2019 22:20:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=1YUfMPM7RT1o5URCsP5/A8wjExy9E/3T5zL1WxdDFpI=; b=Of/aTY0hJb8/Y8LgFZSBARqjQcXchfxSD5iNTcnDOlULWZa4daZ7A8hlQw0ZykEYmt 6H7BIwaVaC9xbm1SBS5wE4HUz57B7kjEToWUDGl07k1GK6bM6Tprs/g5uiaes8UJunWN P/ehAEo7Y6mfbLTYFRrm1HdYexUC/kMcBo9cAs9xQvBKabWTG3c+/0phHbHuDvnrKHal L6eWkZg6xDKqa8TItVpdh1u+hYXMBksKz9P36k7E1vwecyTZxcLqqLPlmaffv45nHy1y sLFH8AB1p/iulP/Nk8KV8wPEGN+Iolfg9k5DoGH6OdRdwkht+1f9MxEA0K6wK7tfMrKl hjWg== X-Gm-Message-State: APjAAAVOB6Gs+OpRjMqRY5uabpd2ZEyMQnG9O4Xi/0ElVnIBxSrmz6Ix eTjLESgnX5+dfTMzcSwouwx1NA== X-Google-Smtp-Source: APXvYqzhrg94zZKMqARZTPlnpBF65FbExNLYEDlH8PaVsNnFFrNS5x/xA9UeSdVBUIhP+KvcD/Laog== X-Received: by 2002:a17:902:b715:: with SMTP id d21mr35489861pls.103.1554787224724; Mon, 08 Apr 2019 22:20:24 -0700 (PDT) Received: from localhost.localdomain ([209.132.188.81]) by smtp.gmail.com with ESMTPSA id y19sm43192451pfn.164.2019.04.08.22.20.19 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 08 Apr 2019 22:20:23 -0700 (PDT) Subject: Re: [PATCH 0/3] support reserving crashkernel above 4G on arm64 kdump To: Chen Zhou , catalin.marinas@arm.com, will.deacon@arm.com, akpm@linux-foundation.org, rppt@linux.ibm.com, ard.biesheuvel@linaro.org, takahiro.akashi@linaro.org Cc: wangkefeng.wang@huawei.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org References: <20190403030546.23718-1-chenzhou10@huawei.com> From: Bhupesh Sharma Message-ID: <49012d55-2020-e2ac-1102-59a5f3911a29@redhat.com> Date: Tue, 9 Apr 2019 13:20:16 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20190403030546.23718-1-chenzhou10@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chen, Thanks for the patchset. Before I review the patches in detail, I have a couple of generic queries. Please see them in-line: On 04/03/2019 11:05 AM, Chen Zhou wrote: > When crashkernel is reserved above 4G in memory, kernel should reserve > some amount of low memory for swiotlb and some DMA buffers. So there may > be two crash kernel regions, one is below 4G, the other is above 4G. > > Crash dump kernel reads more than one crash kernel regions via a dtb > property under node /chosen, > linux,usable-memory-range = . > > Besides, we need to modify kexec-tools: > arm64: support more than one crash kernel regions > > Chen Zhou (3): > arm64: kdump: support reserving crashkernel above 4G > arm64: kdump: support more than one crash kernel regions > kdump: update Documentation about crashkernel on arm64 > > Documentation/admin-guide/kernel-parameters.txt | 4 +- > arch/arm64/kernel/setup.c | 3 + > arch/arm64/mm/init.c | 108 ++++++++++++++++++++---- > include/linux/memblock.h | 1 + > mm/memblock.c | 40 +++++++++ > 5 files changed, 139 insertions(+), 17 deletions(-) I am wondering about the use-case for the same. I remember normally fedora-based arm64 systems can do well with a maximum crashkernel size of <=512MB reserved below the 4G boundary. So, do you mean that for your use-case (may be a huawei board based setup?), you need: - more than 512MB of crashkernel size, or - you want to split the crashkernel reservation across the 4GB boundary irrespective of the crashkernel size value. Thanks, Bhupesh