From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.7 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id A48177D2F0 for ; Thu, 11 Jul 2019 08:12:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728090AbfGKIMJ (ORCPT ); Thu, 11 Jul 2019 04:12:09 -0400 Received: from foss.arm.com ([217.140.110.172]:43146 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727974AbfGKIMJ (ORCPT ); Thu, 11 Jul 2019 04:12:09 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4D5992B; Thu, 11 Jul 2019 01:12:08 -0700 (PDT) Received: from [10.1.25.146] (e111740.arm.com [10.1.25.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A25713F59C; Thu, 11 Jul 2019 01:12:06 -0700 (PDT) Subject: Re: [v1 0/5] allow to reserve memory for normal kexec kernel To: Pavel Tatashin , James Morse Cc: Sasha Levin , Jonathan Corbet , Catalin Marinas , Bhupesh Sharma , Linux Doc Mailing List , kexec mailing list , Linux Kernel Mailing List , James Morris , Eric Biederman , will@kernel.org, linux-arm-kernel References: <20190708211528.12392-1-pasha.tatashin@soleen.com> <2d60f302-5161-638a-76cd-d7d79e5631fe@arm.com> From: Vladimir Murzin Message-ID: <93f99d54-9fe4-a191-4877-080ad78322bb@arm.com> Date: Thu, 11 Jul 2019 09:12:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi, On 7/10/19 4:56 PM, Pavel Tatashin wrote: > On Wed, Jul 10, 2019 at 11:19 AM James Morse wrote: >> >> Hi Pasha, >> >> On 09/07/2019 14:07, Pavel Tatashin wrote: >>>>> Enabling MMU and D-Cache for relocation would essentially require the >>>>> same changes in kernel. Could you please share exactly why these were >>>>> not accepted upstream into kexec-tools? >>>> >>>> Because '--no-checks' is a much simpler alternative. >>>> >>>> More of the discussion: >>>> https://lore.kernel.org/linux-arm-kernel/5599813d-f83c-d154-287a-c131c48292ca@arm.com/ >>>> >>>> While you can make purgatory a fully-fledged operating system, it doesn't really need to >>>> do anything on arm64. Errata-workarounds alone are a reason not do start down this path. >>> >>> Thank you James. I will summaries the information gathered from the >>> yesterday's/today's discussion and add it to the cover letter together >>> with ARM64 tag. I think, the patch series makes sense for ARM64 only, >>> unless there are other platforms that disable caching/MMU during >>> relocation. >> >> I'd prefer not to reserve additional memory for regular kexec just to avoid the relocation. >> If the kernel's relocation work is so painful we can investigate doing it while the MMU is >> enabled. If you can compare regular-kexec with kexec_file_load() you eliminate the >> purgatory part of the work. > > Relocation time is exactly the same for regular-kexec and > kexec_file_load(). So, the relocation is indeed painful for our case. > I am working on adding MMU enabled kernel relocation. Out of curiosity, does enabling only I-cache make a difference? IIRC, it doesn't require setting MMU, in contrast to D-cache. Cheers Vladimir > > Pasha > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >