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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 681CFC4727E for ; Wed, 7 Oct 2020 16:25:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E5D421707 for ; Wed, 7 Oct 2020 16:25:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728591AbgJGQZB (ORCPT ); Wed, 7 Oct 2020 12:25:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:59260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726504AbgJGQZB (ORCPT ); Wed, 7 Oct 2020 12:25:01 -0400 Received: from gaia (unknown [95.149.105.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3B21E216C4; Wed, 7 Oct 2020 16:24:56 +0000 (UTC) Date: Wed, 7 Oct 2020 17:24:53 +0100 From: Catalin Marinas To: chenzhou Cc: will@kernel.org, james.morse@arm.com, tglx@linutronix.de, mingo@redhat.com, dyoung@redhat.com, bhe@redhat.com, corbet@lwn.net, John.P.donnelly@oracle.com, prabhakar.pkin@gmail.com, bhsharma@redhat.com, horms@verge.net.au, robh+dt@kernel.org, arnd@arndb.de, nsaenzjulienne@suse.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-doc@vger.kernel.org, guohanjun@huawei.com, xiexiuqi@huawei.com, huawei.libin@huawei.com, wangkefeng.wang@huawei.com Subject: Re: [PATCH v12 9/9] kdump: update Documentation about crashkernel Message-ID: <20201007162453.GR3462@gaia> References: <20200907134745.25732-1-chenzhou10@huawei.com> <20200907134745.25732-10-chenzhou10@huawei.com> <20201005171936.GD14576@gaia> <8644712d-1331-1efc-1cd2-6da8640145b7@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8644712d-1331-1efc-1cd2-6da8640145b7@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 06, 2020 at 10:10:54AM +0800, chenzhou wrote: > On 2020/10/6 1:19, Catalin Marinas wrote: > > On Mon, Sep 07, 2020 at 09:47:45PM +0800, Chen Zhou wrote: > >> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst > >> index 2da65fef2a1c..549611abc581 100644 > >> --- a/Documentation/admin-guide/kdump/kdump.rst > >> +++ b/Documentation/admin-guide/kdump/kdump.rst > > [...] > >> @@ -316,8 +325,18 @@ Boot into System Kernel > >> kernel will automatically locate the crash kernel image within the > >> first 512MB of RAM if X is not given. > >> > >> - On arm64, use "crashkernel=Y[@X]". Note that the start address of > >> - the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000). > >> + On arm64, use "crashkernel=X" to try low allocation in DMA zone, and > >> + fall back to high allocation if it fails. And go for high allocation > >> + directly if the required size is too large. > >> + We can also use "crashkernel=X,high" to select a high region above > >> + DMA zone, which also tries to allocate at least 256M low memory in > >> + DMA zone automatically. > >> + "crashkernel=Y,low" can be used to allocate specified size low memory > >> + in DMA zone. > >> + For non-RPi4 platforms, change DMA zone memtioned above to DMA32 zone. > > I don't think we should mention non-RPi4 explicitly here. I don't even > > understand what the suggestion is since the only way is to disable > > ZONE_DMA in the kernel config. I'd just stick to ZONE_DMA description > > here. > How about like this: > If the kernel config ZONE_DMA is disabled, just try low allocation in DMA32 zone > and high allocation above DMA32 zone. Something like: "allocate 256M low memory in the DMA zone automatically (or the DMA32 zone if CONFIG_ZONE_DMA is disabled)". I'd keep it short. -- Catalin