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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4BEEAC77B6F for ; Mon, 10 Apr 2023 10:04:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229845AbjDJKEx (ORCPT ); Mon, 10 Apr 2023 06:04:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229562AbjDJKEt (ORCPT ); Mon, 10 Apr 2023 06:04:49 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 846183580; Mon, 10 Apr 2023 03:04:48 -0700 (PDT) Received: from dggpemm500016.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Pw4HZ2W4Pz17Rv2; Mon, 10 Apr 2023 18:01:14 +0800 (CST) Received: from [10.67.108.26] (10.67.108.26) by dggpemm500016.china.huawei.com (7.185.36.25) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Mon, 10 Apr 2023 18:02:41 +0800 Message-ID: <6cadc27d-57fc-d71e-8edb-63f26c494ea2@huawei.com> Date: Mon, 10 Apr 2023 18:02:41 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH -next v3 0/2] support allocating crashkernel above 4G explicitly on riscv Content-Language: en-US To: Simon Horman CC: , , , , , , , , , , , , , , References: <20230406220206.3067006-1-chenjiahao16@huawei.com> From: "chenjiahao (C)" In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.108.26] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500016.china.huawei.com (7.185.36.25) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/7 20:05, Simon Horman wrote: > On Fri, Apr 07, 2023 at 06:02:04AM +0800, Chen Jiahao wrote: >> On riscv, the current crash kernel allocation logic is trying to >> allocate within 32bit addressible memory region by default, if >> failed, try to allocate without 4G restriction. >> >> In need of saving DMA zone memory while allocating a relatively large >> crash kernel region, allocating the reserved memory top down in >> high memory, without overlapping the DMA zone, is a mature solution. >> Hence this patchset introduces the parameter option crashkernel=X,[high,low]. >> >> One can reserve the crash kernel from high memory above DMA zone range >> by explicitly passing "crashkernel=X,high"; or reserve a memory range >> below 4G with "crashkernel=X,low". Besides, there are few rules need >> to take notice: >> 1. "crashkernel=X,[high,low]" will be ignored if "crashkernel=size" >> is specified. >> 2. "crashkernel=X,low" is valid only when "crashkernel=X,high" is passed >> and there is enough memory to be allocated under 4G. >> 3. When allocating crashkernel above 4G and no "crashkernel=X,low" is >> specified, a 128M low memory will be allocated automatically for >> swiotlb bounce buffer. >> See Documentation/admin-guide/kernel-parameters.txt for more information. >> >> To verify loading the crashkernel, adapted kexec-tools is attached below: >> https://github.com/chenjh005/kexec-tools/tree/build-test-riscv-v2 > Are you planning to submit the kexec-tools patches too? Yes, but current adaptation is a little informal. I will submit them later after further tests. BR, Jiahao