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=-8.5 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=ham 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 1FBEFC433E2 for ; Wed, 2 Sep 2020 17:13:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DF723207EA for ; Wed, 2 Sep 2020 17:13:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726490AbgIBRNt (ORCPT ); Wed, 2 Sep 2020 13:13:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:36612 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726269AbgIBRNs (ORCPT ); Wed, 2 Sep 2020 13:13:48 -0400 Received: from gaia (unknown [46.69.195.48]) (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 B3EC72071B; Wed, 2 Sep 2020 17:13:44 +0000 (UTC) Date: Wed, 2 Sep 2020 18:13:42 +0100 From: Catalin Marinas To: Chen Zhou 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 v11 5/5] kdump: update Documentation about crashkernel Message-ID: <20200902171341.GC16673@gaia> References: <20200801130856.86625-1-chenzhou10@huawei.com> <20200801130856.86625-6-chenzhou10@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200801130856.86625-6-chenzhou10@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Sat, Aug 01, 2020 at 09:08:56PM +0800, Chen Zhou wrote: > diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst > index 2da65fef2a1c..4b58f97351d5 100644 > --- a/Documentation/admin-guide/kdump/kdump.rst > +++ b/Documentation/admin-guide/kdump/kdump.rst > @@ -299,7 +299,15 @@ Boot into System Kernel > "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory > starting at physical address 0x01000000 (16MB) for the dump-capture kernel. > > - On x86 and x86_64, use "crashkernel=64M@16M". > + On x86 use "crashkernel=64M@16M". > + > + On x86_64, use "crashkernel=X" to select a region under 4G first, and > + fall back to reserve region above 4G. > + We can also use "crashkernel=X,high" to select a region above 4G, which > + also tries to allocate at least 256M below 4G automatically and > + "crashkernel=Y,low" can be used to allocate specified size low memory. > + Use "crashkernel=Y@X" if you really have to reserve memory from specified > + start address X. > > On ppc64, use "crashkernel=128M@32M". > > @@ -316,8 +324,15 @@ 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 ZONE_DMA, and > + fall back to high allocation if it fails. And go for high allocation > + directly if the required size is too large. If crash_base is outside I wouldn't mention crash_base in the admin guide. That's an implementation detail really and admins are not supposed to read the source code to make sense of the documentation. ZONE_DMA is also a kernel internal, so you'd need to define what it is for arm64. At least the DMA and DMA32 zones are printed during kernel boot. > + ZONE_DMA, try to allocate at least 256M in ZONE_DMA automatically. > + "crashkernel=Y,low" can be used to allocate specified size low memory. > + For non-RPi4 platforms, change ZONE_DMA memtioned above to ZONE_DMA32. > + Use "crashkernel=Y@X" if you really have to reserve memory from > + specified start address X. Note that the start address of the kernel, > + X if explicitly specified, must be aligned to 2MiB (0x200000). -- Catalin