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 DD287C83F12 for ; Tue, 29 Aug 2023 09:55:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234932AbjH2JzJ (ORCPT ); Tue, 29 Aug 2023 05:55:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231666AbjH2Jyl (ORCPT ); Tue, 29 Aug 2023 05:54:41 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 738D9E9; Tue, 29 Aug 2023 02:54:38 -0700 (PDT) Received: from dggpemm500016.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4RZjNP5yT5zhZHV; Tue, 29 Aug 2023 17:50:45 +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 15.1.2507.31; Tue, 29 Aug 2023 17:54:36 +0800 Message-ID: <4b4063c2-dfd3-474b-6827-8dbd1257af2d@huawei.com> Date: Tue, 29 Aug 2023 17:54:35 +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 v9 0/2] support allocating crashkernel above 4G explicitly on riscv To: , , , , , , , , , , , , , , , References: <20230726175000.2536220-1-chenjiahao16@huawei.com> Content-Language: en-US From: "chenjiahao (C)" In-Reply-To: <20230726175000.2536220-1-chenjiahao16@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.108.26] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm500016.china.huawei.com (7.185.36.25) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi folks, This is a friendly ping. Anyone has additional comments on this patch set? Best regards, Jiahao On 2023/7/27 1:49, 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 > > Following test cases have been performed as expected: > 1) crashkernel=256M //low=256M > 2) crashkernel=1G //low=1G > 3) crashkernel=4G //high=4G, low=128M(default) > 4) crashkernel=4G crashkernel=256M,high //high=4G, low=128M(default), high is ignored > 5) crashkernel=4G crashkernel=256M,low //high=4G, low=128M(default), low is ignored > 6) crashkernel=4G,high //high=4G, low=128M(default) > 7) crashkernel=256M,low //low=0M, invalid > 8) crashkernel=4G,high crashkernel=256M,low //high=4G, low=256M > 9) crashkernel=4G,high crashkernel=4G,low //high=0M, low=0M, invalid > 10) crashkernel=512M@0xd0000000 //low=512M > 11) crashkernel=1G,high crashkernel=0M,low //high=1G, low=0M > > Changes since [v9]: > 1. As per Conor's comment, rebase to correct base on riscv/for-next > branch. No code logic changed. > > Changes since [v8]: > 1. Rebase to newest mainline head, not modifying any code logic. > > Changes since [v7]: > 1. Minor refactor: move crash_low_size = DEFAULT_CRASH_KERNEL_LOW_SIZE > into the !high branch when the first allocation fails. Not changing > the result but further align with Arm64 logic, refer to Baoquan's > comment. > 2. Add test case "crashkernel=1G,high crashkernel=0M,low", the result > also matches our expectation. > > Changes since [v6]: > 1. Introduce the "high" flag to mark whether "crashkernel=X,high" > is passed. Fix the retrying logic between "crashkernel=X,high" > case and others when the first allocation attempt fails. > > Changes since [v5]: > 1. Update the crashkernel allocation logic when crashkernel=X,high > is specified. In this case, region above 4G will directly get > reserved as crashkernel, rather than trying lower 32bit allocation > first. > > Changes since [v4]: > 1. Update some imprecise code comments for cmdline parsing. > > Changes since [v3]: > 1. Update to print warning and return explicitly on failure when > crashkernel=size@offset is specified. Not changing the result > in this case but making the logic more straightforward. > 2. Some minor cleanup. > > Changes since [v2]: > 1. Update the allocation logic to ensure the high crashkernel > region is reserved strictly above dma32_phys_limit. > 2. Clean up some minor format problems. > > Chen Jiahao (2): > riscv: kdump: Implement crashkernel=X,[high,low] > docs: kdump: Update the crashkernel description for riscv > > .../admin-guide/kernel-parameters.txt | 15 +-- > arch/riscv/kernel/setup.c | 5 + > arch/riscv/mm/init.c | 93 +++++++++++++++++-- > 3 files changed, 99 insertions(+), 14 deletions(-) >