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 29F59C47095 for ; Mon, 5 Oct 2020 17:19:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E081B20796 for ; Mon, 5 Oct 2020 17:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727527AbgJERTo (ORCPT ); Mon, 5 Oct 2020 13:19:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:46084 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725973AbgJERTn (ORCPT ); Mon, 5 Oct 2020 13:19:43 -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 AF9932078E; Mon, 5 Oct 2020 17:19:39 +0000 (UTC) Date: Mon, 5 Oct 2020 18:19:37 +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 v12 9/9] kdump: update Documentation about crashkernel Message-ID: <20201005171936.GD14576@gaia> References: <20200907134745.25732-1-chenzhou10@huawei.com> <20200907134745.25732-10-chenzhou10@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200907134745.25732-10-chenzhou10@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > + 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). > > Load the Dump-capture Kernel > ============================ > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index a1068742a6df..f7df572d8f64 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -727,6 +727,10 @@ > [KNL, X86-64] Select a region under 4G first, and > fall back to reserve region above 4G when '@offset' > hasn't been specified. > + [KNL, arm64] Try low allocation in DMA zone, fall back > + to high allocation if it fails when '@offset' hasn't been > + specified. For non-RPi4 platforms, change DMA zone to > + DMA32 zone. Same here, unclear what "change DMA zone to DMA32 zone" means. > See Documentation/admin-guide/kdump/kdump.rst for further details. > > crashkernel=range1:size1[,range2:size2,...][@offset] > @@ -743,6 +747,8 @@ > Otherwise memory region will be allocated below 4G, if > available. > It will be ignored if crashkernel=X is specified. > + [KNL, arm64] range in high memory. > + Allow kernel to allocate physical memory region from top. > crashkernel=size[KMG],low > [KNL, X86-64] range under 4G. When crashkernel=X,high > is passed, kernel could allocate physical memory region > @@ -751,13 +757,16 @@ > requires at least 64M+32K low memory, also enough extra > low memory is needed to make sure DMA buffers for 32-bit > devices won't run out. Kernel would try to allocate at > - at least 256M below 4G automatically. > + least 256M below 4G automatically. > This one let user to specify own low range under 4G > for second kernel instead. > 0: to disable low allocation. > It will be ignored when crashkernel=X,high is not used > or memory reserved is below 4G. > - > + [KNL, arm64] range in low memory. > + This one let user to specify a low range in DMA zone for > + crash dump kernel. For non-RPi4 platforms, change DMA zone > + to DMA32 zone. And again here. -- Catalin