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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 DD7E3C43467 for ; Thu, 8 Oct 2020 09:48:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8790020725 for ; Thu, 8 Oct 2020 09:48:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729246AbgJHJsj (ORCPT ); Thu, 8 Oct 2020 05:48:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:39934 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725849AbgJHJsj (ORCPT ); Thu, 8 Oct 2020 05:48:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AAACFADC1; Thu, 8 Oct 2020 09:48:37 +0000 (UTC) Date: Thu, 8 Oct 2020 11:48:36 +0200 From: Joerg Roedel To: Arvind Sankar Cc: x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/5] x86/boot/64: Explicitly map boot_params and command line Message-ID: <20201008094836.GH3209@suse.de> References: <20201007195351.776555-1-nivedita@alum.mit.edu> <20201007195351.776555-5-nivedita@alum.mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201007195351.776555-5-nivedita@alum.mit.edu> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 07, 2020 at 03:53:50PM -0400, Arvind Sankar wrote: > This is fragile, as boot_params and the command line mappings are > required for the main kernel. If EARLY_PRINTK and RANDOMIZE_BASE are > disabled, a QEMU/OVMF boot never accesses the command line in the > decompressor stub, and so it never gets mapped. The main kernel accesses > it from the identity mapping if AMD_MEM_ENCRYPT is enabled, and will > crash. Looked again, and I think that is wrong for boot_params, which are touched unconditionally at the beginning of extract_kernel(). For the cmdline you are right, but one of CONFIG_ACPI, CONFIG_RANDOMIZE_BASE, CONFIG_X86_5LEVEL or CONFIG_EARLY_PRINTK is sufficient to have it touched during this boot stage. Regards, Joerg