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=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 EEE01ECDE5F for ; Mon, 23 Jul 2018 14:34:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A6F7420779 for ; Mon, 23 Jul 2018 14:34:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A6F7420779 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388402AbeGWPgV (ORCPT ); Mon, 23 Jul 2018 11:36:21 -0400 Received: from mx2.suse.de ([195.135.220.15]:39390 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388183AbeGWPgV (ORCPT ); Mon, 23 Jul 2018 11:36:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 73659AD39; Mon, 23 Jul 2018 14:34:46 +0000 (UTC) Date: Mon, 23 Jul 2018 16:34:43 +0200 From: Michal Hocko To: Baoquan He Cc: Andrew Morton , linux-kernel@vger.kernel.org, robh+dt@kernel.org, dan.j.williams@intel.com, nicolas.pitre@linaro.org, josh@joshtriplett.org, fengguang.wu@intel.com, bp@suse.de, andy.shevchenko@gmail.com, patrik.r.jakobsson@gmail.com, airlied@linux.ie, kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, dmitry.torokhov@gmail.com, frowand.list@gmail.com, keith.busch@intel.com, jonathan.derrick@intel.com, lorenzo.pieralisi@arm.com, bhelgaas@google.com, tglx@linutronix.de, brijesh.singh@amd.com, jglisse@redhat.com, thomas.lendacky@amd.com, gregkh@linuxfoundation.org, baiyaowei@cmss.chinamobile.com, richard.weiyang@gmail.com, devel@linuxdriverproject.org, linux-input@vger.kernel.org, linux-nvdimm@lists.01.org, devicetree@vger.kernel.org, linux-pci@vger.kernel.org, ebiederm@xmission.com, vgoyal@redhat.com, dyoung@redhat.com, yinghai@kernel.org, monstr@monstr.eu, davem@davemloft.net, chris@zankel.net, jcmvbkbc@gmail.com, gustavo@padovan.org, maarten.lankhorst@linux.intel.com, seanpaul@chromium.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org Subject: Re: [PATCH v7 4/4] kexec_file: Load kernel at top of system RAM if required Message-ID: <20180723143443.GD18181@dhcp22.suse.cz> References: <20180718024944.577-1-bhe@redhat.com> <20180718024944.577-5-bhe@redhat.com> <20180718153326.b795e9ea7835432a56cd7011@linux-foundation.org> <20180719151753.GB7147@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180719151753.GB7147@localhost.localdomain> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 19-07-18 23:17:53, Baoquan He wrote: > Kexec has been a formal feature in our distro, and customers owning > those kind of very large machine can make use of this feature to speed > up the reboot process. On uefi machine, the kexec_file loading will > search place to put kernel under 4G from top to down. As we know, the > 1st 4G space is DMA32 ZONE, dma, pci mmcfg, bios etc all try to consume > it. It may have possibility to not be able to find a usable space for > kernel/initrd. From the top down of the whole memory space, we don't > have this worry. I do not have the full context here but let me note that you should be careful when doing top-down reservation because you can easily get into hotplugable memory and break the hotremove usecase. We even warn when this is done. See memblock_find_in_range_node -- Michal Hocko SUSE Labs