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=HEADER_FROM_DIFFERENT_DOMAINS, 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 5246DC43381 for ; Thu, 28 Mar 2019 13:21:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 21335206B8 for ; Thu, 28 Mar 2019 13:21:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726601AbfC1NV5 (ORCPT ); Thu, 28 Mar 2019 09:21:57 -0400 Received: from mga12.intel.com ([192.55.52.136]:5371 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725816AbfC1NV5 (ORCPT ); Thu, 28 Mar 2019 09:21:57 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Mar 2019 06:21:57 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,280,1549958400"; d="scan'208";a="138019257" Received: from smile.fi.intel.com (HELO smile) ([10.237.72.86]) by orsmga003.jf.intel.com with ESMTP; 28 Mar 2019 06:21:55 -0700 Received: from andy by smile with local (Exim 4.92) (envelope-from ) id 1h9Uyf-0002nM-T2; Thu, 28 Mar 2019 15:21:53 +0200 Date: Thu, 28 Mar 2019 15:21:53 +0200 From: Andy Shevchenko To: Borislav Petkov Cc: "H. Peter Anvin" , x86@kernel.org, Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 7/7] x86/boot: Support nocfg parameter for earlyprintk Message-ID: <20190328132153.GZ9224@smile.fi.intel.com> References: <20190319184325.72807-1-andriy.shevchenko@linux.intel.com> <20190319184325.72807-8-andriy.shevchenko@linux.intel.com> <20190328130317.GG22720@zn.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190328130317.GG22720@zn.tnic> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 28, 2019 at 02:03:17PM +0100, Borislav Petkov wrote: > On Tue, Mar 19, 2019 at 09:43:25PM +0300, Andy Shevchenko wrote: > > If by BIOS or by other means the serial port is configured > > user might want to skip reconfiguration in the boot code. > > That needs more explanation: how can that happen? I didn't get what is 'that' here? You mean that serial interface becomes configured before kernel even starts? See below. > How is the user > supposed to know whether the serial port is configured in order to use > this cmdline param? If the connection to the target is done via serial interface and firmware and / or bootloader already did necessary configuration. > Why can't the kernel detect whether the serial port is configured and > not touch that configuration? Because it can't at this stage. We simple can't afford to move all serial drivers (even partially) to the _boot_ part of the kernel. > A lot of why's and head scratching... What other why's should be answered? -- With Best Regards, Andy Shevchenko