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 506B7C76196 for ; Fri, 7 Apr 2023 12:05:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240646AbjDGMF2 (ORCPT ); Fri, 7 Apr 2023 08:05:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240678AbjDGMF1 (ORCPT ); Fri, 7 Apr 2023 08:05:27 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D09C58A5B; Fri, 7 Apr 2023 05:05:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6BD1A60F87; Fri, 7 Apr 2023 12:05:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF5B7C433EF; Fri, 7 Apr 2023 12:05:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1680869122; bh=O1PgNY99xnStr1ysLAs1BX2iTotKJxWBIm8q8t8h7FE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=A3BWCBHVMwHlO3r3sfy+Rpi2fFBvTr8G2at1muuXs3wnTMTc12JtAM0jVv1+kmicM uhf+vXhef0GYwiJXXkW815xf+QATj3GYgjLjiNbmdvlokpHx1fkpBiYZRlxnLcQ+Nj 1fhJMDWQUbpH3kVcudRpZTNwRBEy7Dc2sp5F31os8FFSY2SmCXjQNJqMQOgMXAs2Ma gqZPVAQm3CWZcGzoH8oGSMN82djNJJj1rjQPQS05TncXDGZ0uQ4oqoEjcnkRCYr6SX RhBPke7pYYt1uSYVx5OMieBAvYOe29xk+ZvC1cwO5zXEbYzdXiXmAEU4gyfwUz9Bj1 RSYIXBAgYWbMA== Date: Fri, 7 Apr 2023 14:05:17 +0200 From: Simon Horman To: Chen Jiahao Cc: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, kexec@lists.infradead.org, linux-doc@vger.kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, conor.dooley@microchip.com, guoren@kernel.org, heiko@sntech.de, bjorn@rivosinc.com, alex@ghiti.fr, akpm@linux-foundation.org, atishp@rivosinc.com, bhe@redhat.com, thunder.leizhen@huawei.com Subject: Re: [PATCH -next v3 0/2] support allocating crashkernel above 4G explicitly on riscv Message-ID: References: <20230406220206.3067006-1-chenjiahao16@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230406220206.3067006-1-chenjiahao16@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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?